Accounting for systemic effects of anaerobic digestion development on farmers’ practices: implications for environmental assessment

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However, biogas production brings new challenges in agriculture, and it is difficult to draw clear conclusions on its agri-environmental effects from the current scientific literature. Current studies focus on one or more of the agri-environmental effects of on-farm biogas development (mainly greenhouse gas balance, carbon storage, and nitrogen losses), assuming that the farming system as a whole remains unchanged, but they rarely investigate how the performance of biogas relates to indirect changes in farm practices and activities. To better understand the changes in farm practices linked to biogas production, we surveyed 23 biogas farmers corresponding to 19 different on-farm biogas units in two areas of northeast France. We aimed to cover a diversity of configurations (e.g., of farm activities, installed biogas capacity, number of biogas farmers per project, and energy recovery methods) to capture a diversity of farm functioning. We analyzed these qualitative data by looking for recurring examples of changes in practices (or lack thereof) and drivers of the identified changes. Our results show various changes in practices and drivers of change resulting in a much more diverse range of environmental impacts than those generally assessed in the literature. This diversity of impacts depends on both the farm characteristics and the different organizations of farm activities that biogas farmers can develop. Here we show that the necessary conditions to attain the best environmental balance are not always met, contrary to the common assumptions in the biogas assessment literature. On-farm biogas sustainability research must better consider the dynamics of farming systems and the agency of farmers in on-farm biogas development. Biogas sustainability practices’ change anaerobic digestion systemic effects diversity farming system Figures Figure 1 1. Introduction Since the beginning of the 21st century, biogas produced from anaerobic digestion (AD) has developed around the world. Biogas production is mainly supported for its contribution to the energy transition, as a renewable decarbonized gas. The environmental impacts of AD vary greatly from one country to another, according to the feedstock digested (crops, manure, agricultural residues, biowaste), the technical options (AD unit technology, digestate management practices) and the magnitude of its development. In Europe, Germany is an example of high AD development: it has facilitated an increased in decarbonized electricity production, but at the same time, has seen negative impacts on biodiversity (Vergara and Lakes 2019 ) and food prices (Britz and Delzeit 2013 ). In France, AD was developed in agriculture (Fig. 1 ) with the aim of avoiding the negative agri-environmental impacts observed in Germany. French biogas policy has even supported biogas production for its contribution to sustainable agriculture. The current environmental balance of biogas in France is under debate, and the scientific literature has failed to draw clear conclusions on its agri-environmental impacts (Moinard 2021 ; Malet 2022 ; Cadiou et al. 2023 ). In this paper, we identify two main categories of studies that address this issue. The first category, which is the larger of the two, focuses on one or more of the agri-environmental effects of on-farm biogas development (mainly greenhouse gas balance, biodiversity, carbon storage, and nitrogen losses), assuming that the farming system as a whole remains unchanged. The literature in this category tends to assess direct changes limited to a few agricultural practices (Quakernack et al. 2012 ; Möller 2015 ; Bacenetti et al. 2016 ; Nicholson et al. 2017 ; Paolini et al. 2018 ; Greenberg et al. 2019 ; Launay et al. 2020 ; Esnouf et al. 2021 ), such as new methods of digestate fertilization, the introduction of energy cover crops, and manure digestion. Although these assessments analyse a range of different practices, they do not consider the systemic interactions between them. In general, the literature in this category assumes that farmers adopt the “best practices” recommended by agronomists (Cadiou et al. 2023 ) and that certain agri-environmental effects are rather consensual. For example, the view may be expressed that adopting best practices will improve the greenhouse gas (GHG) balance, which can bring climate benefits (Hijazi et al. 2016 ; Bacenetti et al. 2016 ; Ingrao et al. 2019 ; Malet 2022 ); or that increased use of digestate fertilizer decreases the need for synthetic nitrogen, if the best spreading practices are adopted (Clements et al. 2012 ; Nkoa 2014 ; Koszel and Lorencowicz 2015 ; Guilayn et al. 2019 ). Without the adoption of best practices, increased use of digestate could increase the risk of air (Nkoa 2014 ; Carton and Bulcke 2021 ; Moinard 2021 ) and water pollution (Möller 2015 ; Nicholson et al. 2017 , 2018 ; Räbiger et al. 2020 ; Purswani and Llorente 2021 ). Other issues lack consensus or are even the subject of contradictory conclusions, such as the effects of digestate on soil carbon, which depends considerably on return-to-soil practices (Moinard 2021 ). Finally, the literature in this category contains much uncertainty on some issues, because the long-term perspective remains poorly documented, such as the impacts of digestate spreading on soil biology (Sadet-Bourgeteau et al. 2020 ; van Midden et al. 2023 ) and the impacts of AD on soil compaction and regional biodiversity. The second category of literature, which is much smaller, identifies indirect mechanisms that can influence the adoption of practices, highlighting that, as well as direct change, the development of AD on farms sometimes triggers changes in practices in other farm activities. Thus Beausang et al. ( 2021 ) show that the sustainability of grass silage used as an AD feedstock, depends on whether it indirectly displaces feed for livestock elsewhere. Carton & Levavasseur ( 2022 ) show that soil carbon storage and biodiversity vary from one farm to another, on the introduction of energy cover crops to supply the AD unit. In Germany, Blumenstein et al. ( 2018 ) and Siegmeier et al. ( 2015 ) show, through qualitative modelling, that in some AD farms, higher crop yields and improved nitrogen management are coupled with a reducing labor and less energy costs. This body of research shows that the environmental performance of biogas can be related to other changes in the functioning of the farm or of the territory, even though few works really explore these links. Other papers show unexpected social, economic, and ecological outcomes. In Italy, an increase in a farm’s bioenergy crop production (Carrosio 2014 ; Cavicchi 2016 ) or a territorial-level increase in the need for biomass as an AD feedstock can lead to increases in farmland rent, which in turn can influence agricultural systems. In Germany, in the 2010s, AD development led to a huge increase in maize production, increased land prices, and increased food prices (Lüker-Jans et al. 2017 ; Vergara and Lakes 2019 ). Based on these two categories of literature, it is difficult to draw clear conclusions on the environmental impacts of on-farm biogas development. Very few studies empirically assess the impacts of AD looking at systemic mechanisms and their influence on several agri-environmental aspects. This article aims to contribute to the understanding of the real effects of AD on farming practices and therefore on the sustainability pathways of farms by answering the following two questions: how does on-farm AD development change farm practices?; and what are the related agri-environmental impacts? To this end, we mobilize the “farming system studies” framework, which assumes that a system approach is necessary to capture the reasoning that underlies practices and their evolution (Sebillotte 1974 ; Biggs 1985 ). It considers the agricultural system through the interaction between three scales: technical systems (field scale), production systems (farm scale) and agricultural territory (landscape scale) (Darnhofer et al. 2012 ; Cochet 2012 ). Technical systems include highly interconnected cropping, livestock and forage systems: changing a practice in one technical system often affects other practices within the system, and other systems (Meynard et al. 2001 ). This approach also enables us to understand the trade-offs between production factors (labour, land, expertise) on a farm, and how this influences technical systems. AD is a new farm technical system that can modify the existing links between and within other technical systems (cropping, livestock…). Beyond the consideration of AD as a technical system, its development necessarily requires the allocation of production factors. This, in turn, has consequences on the overall functioning of the farming system (Cochet et al. 2007 ). Such changes must be understood through “the meaning that actors give to [them]” (Darnhofer et al. 2012 ). The concept of “situated rationality” puts farmer strategies at the heart of the evolution of farming systems, viewing them as stakeholders and drivers of the emergence of new forms of sociotechnical organization (Osty et al. 1998 ). This framework moves us away from an analysis of biogas development based on “rational modernization” and towards an understanding of the underlying “logic” of farmers, knowing that they may have conflicting goals. Finally, this article puts forward the following hypothesis: changes in practices associated with the management of AD units can be linked to indirect mechanisms involving other practices, other farm activities, and even regional dynamics, resulting in a much more diverse range of environmental impacts than the effects generally documented in the literature. 2. Material and Methods We surveyed 23 AD farmers in two French areas, Vosges and Bas-Rhin (northeast France) corresponding to 19 different on-farm AD units. The two areas differed in terms of (i) AD type (mostly combined heat and power (CHP) in Vosges, compared to biomethane injection in Bas-Rhin) and (ii) agricultural context (predominantly mixed farming in Vosges compared to more diversified production in Bas-Rhin, with field crops, mixed farming, market gardening, pigs and poultry). The aim was to cover a diversity of configurations based on the following criteria: Activity of the farm contacted (suckler, dairy, mixed farming, pig farming, cereals) Number of AD unit project owners (individual, small or medium-sized collective) Installed capacity of the unit Energy recovery method (CHP or injection, and on-farm energy recovery activity) We tried to select the surveyed unit based on the digested feedstocks insofar as we were able to gather information on this criterion before the survey. We also selected biogas plants with a start-up date preferably before 2018, to gain perspective on farming systems changes. The choice of respondents therefore followed the “snowball sampling” method, to enable evolution in our field of investigation (Biernacki and Waldorf 1981 ; Handcock and Gile 2011 ): this approach involves making contact with an initial farmer, who then refers us to other farmers, from whom we get further referrals, and so on. In parallel, we gathered information on AD units and farms from technical publications, from AD unit websites, and from interviews with local stakeholders, to better select the farms surveyed according to our criteria. We stopped snowball sampling once we had covered a diverse range: in Vosges we surveyed 25% of the AD units in operation in 2021, and 50% in Bas-Rhin. Each farmer was interviewed for two to three hours, in two stages: a semi-structured interview in 2021, including a visit to the AD site, except for three farmers for whom the interview was conducted by phone; followed by a complementary semi-structured phone interview between January and June 2022. The author transcribed the interviews. Each farmer is designated by a letter. Interviews began by gathering data on (i) current farming systems and the technical AD system; and (ii) the origin and history of the AD project. The interview then moved to a discussion of the ways in which AD had modified the farm, focusing on the following points: Whether or not the farming system, technical systems and practices had changed following the start of the AD project; The interactions between farming system components, and potentially the interactions between other regional variables/components (other farms, food industry); The rationale behind these changes, or the maintenance of previous practices. Table 1 Characteristics of farms and AD units surveyed (from (Cadiou 2023 ) ). * It includes arable land and permanent grassland. Region Vosges Bas-Rhin Number of farms for each agricultural activity Multi-crop dairy 3 2 Mixed crop-livestock 6 4 Grass-fed meat farming (sheep and cattle) 1 1 Cereal 1 2 Monogastric livestock 0 3 Farm area characteristics: average and [range of variation] Average total cultivated area* (ha) 330 [80–680] 146 [40–370] Average area of permanent grassland (ha) 134 [25–360] 47 [0-150] Number of farmers having invested in the AD unit Individual unit (N = 1) 6 5 Small collective unit (N = 2) 1 2 Medium collective unit N = [4–7] 3 2 Total number of AD units surveyed 10 9 Total number of AD farmers surveyed 11 12 Year of unit start-up Interval between the oldest unit and the most recent unit [2013–2019] [2012–2020] Average installed capacity of units surveyed Cogeneration of heat and power (kW) 404 542 Biomethane injection (Nm3) 140 218 Biogas recovery method (cogeneration or injection) Number of cogeneration units out of total number of units 9 out of 10 5 out of 9 We analysed the data by looking for recurring examples of changes in practices (or lack of change) and of the drivers of the changes identified. In this way we have identified three main areas of technical change: crop rotations, fertilization, and forage and permanent grassland management. Data collected in the interviews on the description of practices were mainly qualitative and based on the observations of farmers. During the initial interviews, there was a back and forth with the literature to identify variables accessible to farmers, which enabled us to describe practices and to link them with agri-environmental effects based on the scientific literature. To characterize the sustainability of fertilization practices, we collected data on the digestate doses applied, the application calendar, application equipment, changes in mineral nitrogen fertilization, constraints, and levers for implementing good practices, and estimated nitrogen fertilizer savings on farms. Regarding the evolution of cropping systems, we collected data on crop succession, technical interventions (treatments, tillage), and the links between AD supply and crop rotation planning. Regarding forage management, we collected data on the evolution of forage cultivation (surface area, species, technical interventions) as well as on the established links between anaerobic digestion and livestock farming. 3. Results 3.1. Changes in crop rotations In the two areas studied, AD is developing by valorizing livestock manure, supplemented by more methanogenic feedstock such as energy crops, cover crops, crop residues, biowaste and by-products (see Table 2 ). Manure digestate is supported by French law, with a “manure” prime which gets to its maximum for a 60% manure supply or more. Table 2 Supply of surveyed AD plants (average percentage by volume of raw material according to feedstock category and ranges of variation in our sample). Source: farmers. Average percentage [variation range] per area 10 Vosges units 9 Bas-Rhin units Average percentage of livestock manure 71% [35–83%] 66% [30–90%] Average percentage of by-product (agricultural or agro-industrial) and biowaste 8% [0–16%] 22% [5–60%] Average percentage of energy crops 12% [5–45%] 4% [3–17%] Average percentage of energy cover crops 6% [4–18%] 7% [0–42%] These differentiated supplies depend on the available feedstock in the area, which in turn influences strategies for changing cropping systems. We have identified four different patterns of change: Pattern 1: Maintaining previous crops and marginal changes to the cropping system (two farmers) . The initial rotation changed little, the introduction of new energy cover crops (ECC) for the AD plant remaining marginal. Q and R farmers have only modified their summer ECC for biogas production (maize, sorghum, or mixed crops), as they didn’t want to affect the yields of their spring crops. But they did not rely on these summer ECC crops to supply the biogas plant, because of their low yields, due to summer drought. These farmers feed their AD unit with a diversified mix of feedstock harvested in the area: agricultural co-products (maize stover (R), livestock effluents (Q, R)), bio-waste (R), agro-industrial by-products (Q). Pattern 2: Maintaining previous crops and developing ECC (3 farmers). The farmers (J, O, T) have chosen to produce more biomass via winter or summer ECC, for biogas production, without however modifying the succession of main crops: T and J cover their soils extensively in winter with rye and ryegrass (80ha and 40ha respectively at J), while farmer O has introduced around 20 ha of winter CIVE, and has increased his summer ECC area further - even though it is not very productive. The most methanogenic feedstocks come in part from off-farm purchases, such as bio-waste (O) and agro-industrial co-products (J, O, T), which are supplemented by winter CIVE. Pattern 3: Modification of the cropping system to contribute to biogas production by introducing energy crops and ECC (12 farmers). Most farmers have modified their rotations to introduce energy and ECC to supply the AD units. Eleven farmers have increased their area under maize silage, and two farmers have introduced a triticale and rye mix intercrop. These crops replace cash crops, mostly cereals (A, C, E, H, I, V), but also rapeseed (B, G), and grain maize (K, L, M, S, V) (see Table 3 ). As in pattern 2, farmers have introduced ECC either between their main crops or following energy crops. Most farmers chose winter ECC (rye, triticale, meslin) or temporary ryegrass-type meadows (A, B, C, E, G, H, I, M, S, V, W), which are methanogenic, and whose production per hectare is regarded as good (A, B, E, G, H, M, S, V, W). Compared with pattern 2, some farmers have accepted that double cropping affects maize yield (main crop) because the average net margin per hectare is better from their point of view (B, C, G, H, I, S, V, W). Others have preferred not to grow a double crop including maize, as the double crop affects the maize yield too much (A, E, L), so they have switched to an energy winter crop that is maintained on the field for longer: therefore, growing a winter rye followed by a temporary grassland or a summer ECC (A, E). Growing these crops on their own ensures autonomy in supplying the AD unit and means that they are not dependent on the availability and price of feedstocks purchased locally. Table 3 Changes in crop rotation for Pattern 3 farmers with the development of AD Farmer Stopped cultivation… Replaced by… Double cropping (if concerned) A 5–6 ha of cereals 7–8 ha of permanent grassland 12–14 ha of rye Few ha of maize Double cropping possible depending on the year and the plot B 15–20 ha of rapeseed 15–20 ha of maize 10–15 ha of ryegrass (ECC) 50ha of summer ECC (mix of grasses and legumes) Double cropping before maize C 20 ha of barley 20 ha of maize Partial reintroduction of temporary grassland (alfalfa, clover) Double cropping with yield loss on the following maize crop E 30–40 ha of cereals 40 ha of rye, followed by a three-year ryegrass No double cropping because of the maize yield loss G 15 ha of rapeseed 15 ha of maize 65 ha of winter cover crops (15ha of rye, 50 ha of ryegrass) Few ha of summer ECC Double cropping before maize H x ha of permanent grassland (25-x) ha of triticale and clover 25 ha of maize/sorghum 25 ha of rye (ECC) Double cropping with yield loss on the following maize crop I 4–5 ha of permanent grassland 2ha of barley 6–7 ha of maize Few ha of temporary grassland cover K 25 ha of permanent grassland 10ha of maize 10–15 ha of alfalfa + 10 ha of cash crops 10 ha of rye followed by clover temporary grassland Increase in summer ECC L 15 ha of grain maize 15 ha of silage maize Adaptation of summer ECC species for biogas production M 20 ha of grain maize 20 ha of silage maize 15ha of rye (ECC) Few ha of ryegrass S 10 ha of grain maize 10 ha of silage maize 20-30ha of rye or ryegrass Double cropping with yield loss on the following maize crop V Varies from year to year: a few ha of irrigated grain maize Variable from year to year: a few ha of irrigated silage maize or sorghum, or other irrigated summer ECC Various surface of winter ECC Double cropping only on conventional crops W 12 ha of wheat and barley 12 ha of triticale-rye Double cropping with yield loss on the following maize crop Pattern 4: A major transformation of the cropping system linked to the dynamics of the agricultural activity in which AD takes place (four farmers). For some farmers, the development of AD is associated with major changes in their production activities. Three farms converted to organic farming in connection with AD. By fertilizing their organic crops with digestate, these farmers have significantly increased their yields (close to conventional farming yields), enabling them to make significant economic gains. “We wondered about going organic at the same time. The Chamber of Agriculture told us that we were crazy, that we would never grow enough to feed the AD plant, but then after a year of operation (...) we said to ourselves, why not go organic, especially because the digestate solves the fertilizer problem. And we also said to ourselves, if a crop fails in organic farming, we'll still be able to make the AD plant work, we won't have any dry losses. So finally, the conversion went more smoothly" (Farmer D) Farmer U chose to remain in conventional production but saw that AD opened an opportunity to transform his whole farming activity: he diversified by introducing new activities (AD unit, milk processing workshop) and changed his cropping system to supply AD and make his dairy farm more resilient. As part of these structural transformations, farmers have developed ECC cultivation in different ways. In organic arable farming, D opted for ECC followed by temporary grassland, as double cropping reduced maize yields too much (Table 3 , line 2). He also buys conventional maize silage to supply his AD unit. Farmer N has integrated ECC into his rotation, he is due to supply the collective unit (Table 3 , line 3). To do so, he has diversified his rotation from maize//wheat and green manure crop//beet; to wheat/ rye (ECC) //buckwheat/ triticale (ECC) //temporary grassland with clover (one year) ( where “/” denotes intra-annual succession and “//” is inter-annual succession). For F and U, the evolution of the rotation is more closely linked to changes in their livestock farming. Both farmers switched from maize-based animal feed to a grass-based diet (F, U) combined with a cessation of maize in the crop rotation. Farmer F did not introduce energy crops or ECC as he was already supplying his AD unit without difficulty: he has links with a biowaste processing company through which he has access to the biowaste and agro-industrial co-products market. Farmer U, on the other hand, has introduced meslin energy crops into his rotation. To increase his crop production (AD and cows), he ploughed up 10 ha of permanent grassland. Beyond the individual characteristics of farmers, we can identify three drivers that influence the patterns of change: Access and/or dependence on a market for methanogenic feedstocks. The farmers with the oldest AD units [beginning in 2012–2016] stress the fact that the price of co-products and bio-waste has risen considerably in recent years. Eleven farmers mention that, eight years ago, they were able to obtain these products at low cost or even free of charge, whereas now they face ever-increasing prices. For example, in 2021 farmer E bought mustard by-products for €56/tonne, compared to €28/tonne in 2013. The calculation of the biogas generated from a feedstock is at the heart of the construction of the supply of biogas plants: faced with the rising price of by-products, farmers adopted various strategies and decided whether to buy by-products, and whether to produce crops on their farms. Farmer T, for example, explained that to keep costs under control, he shifted his AD supply away from co-products and towards CIVE and energy crops (corn) – which equates to a recent change from pattern 2 to pattern 3. Conversely, farmer R, who does not want to produce more crops on his farm, has tried to diversify his supply with biowaste, which is less expensive than co-products (pattern 1). These dynamics show the importance of the structuring of the territorial biomass market in the development of crop successions. We show that, depending on a farmer’s objectives and the market for feedstocks, this quest for feedstock autonomy opens up different rotation patterns - within the regulatory limit of a maximum of 15% energy crops in the supply. The profitability requirement of the biogas plant. For farmers heavily dependent on ECC, the management of ECC is guided by the objective to produce as much biogas as possible. Since cultivating ECC requires more work than buying feedstock from outside the farm, it must be profitable. Farmers therefore often choose cereal (rye, triticale, meslin) for winter ECC and corn for summer ECC: which produces a lot of biomass. Among the farmers surveyed, two introduced legumes, marginally, via their summer (B) or winter (I) ECC. Reintroducing legumes does not serve their main objective, which is to produce as much biomass as possible. Synergy between organic farming and AD: a driver towards more diversified cropping systems. We observed synergies between AD and organic farming, involving the use of digestate as fertilizer. Among AD farmers who were converting to organic, this process leads to systemic changes in production systems, such as the lengthening and diversification of cropping systems. However, as two farmers demonstrated, the joint economic optimization of food and biogas production may rely on the purchase of non-organic crops from neighboring farmers (via biowaste for F, or via the purchase of manure and maize silage for D). 3.2. Changes in fertilization practices Fertilization practices have evolved with the start of AD for almost every farmer surveyed, since there is a need to manage digestate on their farms. P is the exception: as a mountain sheep farmer, it would not be feasible to spread digestate on his grassland. The way each farmer uses digestate influences to a greater or lesser extent his consumption of synthetic mineral nitrogen, depending on whether he replaces his mineral fertilizer applications with digestate. A first group of six farmers do not reduce their use of synthetic fertilizer, or make only marginal reductions. They adopt the following practices: spreading digestate on crops before sowing corn, or when sowing cereals in autumn (E, H, Q, I), the remaining digestate is spread on grassland in autumn (C, E, K, I). There are three main reasons for the limited application of digestate to cereals in spring: (i) soils often have a low carrying capacity in spring, whereas spreading equipment is heavy (C, E, H, I, K, Q) and large volumes are needed to reach the necessary nitrogen supply for cereals; (ii) spreading takes a long time in spring (large volumes) (E, H, K); and (iii) farmers are concerned that spreading could damage seedlings that have just emerged (I). In autumn, on the other hand, there is a need to empty the slurry pit before winter, which leads to spreading at this time (E, K, H, I). New requirements for mineral nitrogen have also arisen on these farms, with the use of mineral nitrogen on crops destined for AD (E, H, I, K). "We don't want to spread at all in winter, so in October the tank has to be empty (...) because in spring we're not sure we'll be able to spread , and then in spring I do all the fields that have a sufficient soil bearing capacity" (Farmer C). Nine other farmers identify similar constraints influencing their practices (B, G, J, M, O, R, S, T, U). However, they are able to make bigger reductions in synthetic nitrogen use because of their willingness to spread digestate on winter wheat or barley in spring, whenever possible. Their success in this regard is linked to manpower, work schedules and spreading techniques (see below). Farmer U has been able to make even greater reductions in synthetic fertilizer use as a result of decreasing his milk production, and therefore adopting a spreading system that is sufficient for his low production objectives. The other four farmers (D, F, N, V) face similar spreading constraints but have significantly reduced their consumption of mineral nitrogen as they have partially or fully converted to organic farming. These different levels of reductions in nitrogen consumption are linked to the equipment and organization of spreading, that influence the speed of the spreading (characterized notably by the flow rate of the spreader and by the complexity to use the spreader) and the weight of the spreader, associated with risks of compaction. Equipment and practices adopted due to “low resources” - Farmer I (Table 5 , column 2) decided to invest in a small slurry spreader (11 m3), because he could not afford a larger one, and its output is sufficient to spread on his small, grouped fields. Even though the spreader is light, nitrogen savings are limited because nozzle spreading can increase digestate nitrogen volatilization. Equipment and practices adopted to achieve “weight-rate compromise" - farmers (B, C, E, F, H, K, L, M, N, Q, S, T, U, W) have sought a compromise between flow rate (hence working time and spreading efficiency) and equipment weight (risk of compaction). This choice is associated with a diversity of practices linked to personal objectives and resources: B, C, K, M, S and W spread in spring when they consider compaction risk to be limited; H and U practice minimum tillage to improve carrying capacity; B, C, H, K and L have invested in technical solutions to limit compaction (polypropylene tank, 3-axle tank, "low-pressure" tyres, decompaction tools); S increased site efficiency by transporting digestate to the field with a larger slurry tank (24 m 3 ), and then spreading with a 18 m 3 tank. Farmer T has a self-propelled machine that enters the field without a tank, but which has storage for digestate that he fills up off the field. Farmers E and Q have opted for high throughput spreading (21 m 3 - 28 m 3 tank), with the aim of spreading large volumes of digestate and limiting spreading time. However, this practice limits the areas that can be spread in spring, and therefore also limits potential reductions in mineral fertilizer use. For these farmers, such practices result in a range of reductions in nitrogen fertilizer use (Table 5 , column 3). Other farmers, such as M, N and F consider that it is in their economic interest to spread at the optimum time for the crop, which is spring, even if this increases the risk of compaction. Overall, these practices can reduce mineral nitrogen use considerably (Table 5 , column 3, lines 3–4). “Optimization of valorization" practices - farmers D, G, J, O, R and V have sought to extend their spreading window by investing in slurry tanks of different sizes, and/or by combining slurry tank spreading with "tank free" spreading. Such tank-free equipment transports the digestate to the spreader via hoses, thus greatly reducing the weight in the field. This enables the extension of the spreading window, with less risk of compaction and plant mortality compared to spreading with a tank. As a result, these farmers save more on mineral fertilizers (Table 5 , column 5). Most use service providers (A, G, J, O), as these operations are more complex and require more manpower and equipment than most farmers have. Over a certain field size, such equipment has a better throughput than equipment with a tank, but it is expensive. This system and equipment enable significant reductions in nitrogen fertilizer use, to a greater or lesser extent depending on the farm (last column of Table 5 ). The different objectives of farmers, and their resources and constraints are therefore translated into a diversity of spreading practices, with various consequences in terms of reducing mineral nitrogen consumption. Table 5 Diversity of relationships between fertilization practices and choice of spreading equipment and strategy. Farmer A is excluded from the classification as his fertilization system is too unstable to be analysed. Farmers L and W are included in the analysis, even though the recent and still incomplete implementation of certain practices suggests that these practices are likely to evolve in time. P is not included as he does not spread digestate on his farm. Savings /spreading practices “Low resource” “Weight-rate compromise" “Optimization of valorization" 0% or slight diminution I C, E, H, K, L, Q, W Significant decrease (between 30% and 60%) B, M, S G, J, O, R Strong decrease (Between 70% and 100%) F, N, U, T D, V The choice of spreading equipment also includes the choice of techniques for depositing and/or burying digestate. In our surveys, all but one farmer used a dribble bar to limit ammonia volatilization; most bought this equipment when the AD was installed. The farmer (I) who did not invest in a dribble bar did so because he prefers smaller, less expensive equipment, even if it means losing nitrogen through volatilization. Two farmers spoke about problems with clogged pipes (W, H): H prefers to use splash plate spreading in winter, which avoids the risk of frozen digestate clogging the pipes. Eighteen out of 21 farmers, however, have no specific digestate burying equipment, because: (i) it is too expensive (nine farmers); (ii) it requires too much power, so would require reinvestment in a new tractor (ten farmers); (iii) it spreads over a smaller width, so would require more passes over the field (ten farmers); or (iv) it is not practical for spreading on grassland (S). Seven of these 18 farmers plough the digestate into the land quickly (just after or on the same day) when spreading before sowing by tilling (stubble cultivator, disc or harrow), to limit nitrogen losses. The work schedule may delay soil preparation, as in the case of farmer M, who harrows when he has available manpower. The last three farmers (C, Q, T) have invested in equipment that can tow a burying ramp and has a high work rate, with the goal of reducing nitrogen losses. All three had sufficient manpower to manage spreading and the economic capacity to invest in this equipment. 3.3. Changes in forage and permanent grasslands management With the development of AD, six farmers (A, B, E, G, K, J) have decided to produce more fodder crops (maize, temporary meadows) and to stockpile more in anticipation of potential drought: these farmers report that if stockpiles are not used in livestock farming a last-resort economic outlet exists in AD. By guaranteeing a way to valorize plant biomass, AD gives these farmers greater flexibility in forage management. "This year we made a rye-clover mixture to make a second-cut clover. Depending on forage stocks, the rye may or may not be used for AD" (Farmer K). Conversely, other farmers (B, C, H, J, M) used the crops planned for AD as animal feed. While other farmers (A, K, B, J, Q, R) considered that they could afford to buy external maize or other products for AD - which is less the case for livestock farming. They therefore prioritize the use of their own farm-grown crops for livestock production. Other farmers (K, O), due to repeated droughts and low ECC and corn production, buy corn silage to supplement their AD crops. "Initially intended for AD, the rye has been partly conserved for cows (5ha). The sorghum produced in 2022 will also be used primarily for cows, depending on needs. AD still requires the purchase of silage maize" (Farmer M) More broadly, the arrival of AD is bringing about changes on farms that are influencing the management of permanent grasslands. In the Vosges and Bas-Rhin areas, farmers say that they fertilize permanent grasslands more than before AD. The farmers who significantly increased their grassland fertilization were those who had previously fertilized little (A, E, J, K, T, W) with slurry/manure, and had now started to fertilize with digestate. Other farmers who used to fertilize with mineral nitrogen (between 15 and 65kgN/ha) have also increased their fertilization (B, C, H, M, S). They fertilize more because the meadows are easily spreadable before winter, when the digestate pit must be emptied (see 3.2). This change in fertilization has resulted in an increase in grass yields, noted by 12 farmers, and consequently a change in grassland management and grass consumption strategies for some of these farmers: C and J now sell more grass. A, H, I and K have ploughed grassland areas to produce more cash crops, for livestock and for AD. A, B, C, D, I and K use their surplus grass from permanent grassland for AD, generally the 2nd and 3rd cuts, which are of poorer quality for cows. Some farmers (E, G, H, J) also use temporary grassland for AD. Behind these different changes in practices, we can identify two important drivers: Competition or synergy between AD and livestock farming : The economic attractiveness of anaerobic digestion is a key factor in encouraging farmers to adopt AD. Seven farmers said that for the same amount of work, an AD unit is more profitable than livestock. Changes in forage management practices depend on the economic choices made by farmers around the adoption of these activities, and on the economic benefits delivered by AD. Some farmers have made livestock farming a priority: they emphasize their attachment to the livestock profession and a desire to maintain these activities, even if there would be greater economic benefit in prioritizing AD feeding (J, B, O). Some farmers were initially reluctant to use corn or other crops for AD, but ultimately decided to do so. Other farmers plan to prioritize AD over livestock farming or the production of cash crops (I, K), because of economic considerations. Other farmers have also made the financial decision to invest in AD instead of livestock: C and E have disposed of beef finishing units to devote more resources (fodder and labour) to AD. Digestate that can be used to intensify permanent grassland : AD introduces a new organic fertilizer to the farm that can easily be used on permanent grassland. As discussed in section 3.2, spring spreading constraints mean that autumn spreading on grassland is sometimes favoured by farmers, enabling them to intensify forage production. AD is therefore indirectly changing grassland management practices, the composition of animal feed and land use. 4. Discussion 4.1 Understanding changes in practices involves considering the agency of farmers and the dynamics of farming systems. As discussed in the introduction, there has been little research into the influence of AD on farming practices that also consider the mechanisms of systemic changes at the farm level. First, we showed that the evolution of the organization of farm activities plays a role in the development of a diversity of practices. These results are in line with the few studies that have highlighted that the creation of AD on a farm has a major influence on its socio-economic organization (Emmann et al. 2013 ; Carrosio 2014 ; Grouiez et al. 2020 ). The synergies or competition between livestock rearing and AD on forage management illustrate the importance of considering interactions between farm activities to assess AD impacts. Some mechanisms have been identified, such as the increase or loss of forage autonomy (Solagro 2018 ), and the increase in animal husbandry (Carrosio 2014 ), while structural synergies between AD and organic farming have already been studied in Germany (Siegmeier et al. 2015 ). Our empirical work also shows that digestate production on AD farms can facilitate the transition to organic farming. However, AD raises the question of closing the nitrogen cycle, an issue that is not tackled in the scientific literature. If an AD unit on an organic farm is fed at least in part by products from conventional farms, then the synergy between organic farming and AD depends indirectly on the use of mineral fertilizers on these conventional farms. These circumstances may not encourage the closing of the nitrogen cycle with the development of legume crops (as a main or cover crop). At the territorial level, to our knowledge there has been no research into the regional dynamics of AD development, and how this can influence farm practices. We show that the availability of methanogenic feedstock on the territory can influence the evolution of cropping systems. This result is in line with (Cadiou 2023 ), who showed that a rapid increase in the number of AD units in a territory could create competition among farmers for access to feedstock (agro-industrial by-products, manure from surrounding farms, maize). Secondly, regarding digestate spreading, we have shown that farm characteristics (field size, economic resources, farmer knowledge, manpower) make certain technical solutions either beneficial or feasible: the choice of spreading equipment and techniques depends on a multiplicity of factors linked to the farm, which are independent of the AD system. On this subject, our results converge with those of (Carton and Levavasseur 2022 ) and (Markard et al. 2016 ), and with the literature on farming system research (Ingram 2008 ; Toffolini et al. 2017 ), which show that choices of practices depend very much on a farmer’s previous knowledge and practices, and not only on the best available or recommended technical solutions. Farmers may also pursue diverse farm management objectives (maintenance of livestock, increased income, better allocation of work time etc.) that open up additional digestate management options. For example, some farmers view digestate as a cumbersome by-product that requires a lot of work, while for others (such as organic farmers), digestate is a new fertilization opportunity that offers economic gains and greater autonomy. As a result, the nitrogen in digestate would be used inefficiently by the former, while the latter would opt for practices that optimize nitrogen use. In this way, a better understanding of the agency of AD farmers can help identify the obstacles and levers to good practices. In fact, our results take issue with the hypotheses of economic rationality and technique optimization - which are established in the technology development literature (Geels and Smith 2000 ; Wangel 2011 ) – by highlighting the importance of the diversity of situations faced by farmers and their motivations. Thus, considering the diversity of farms and the agency of farmers, we show that actual practices can be more varied than previously documented. These indirect mechanisms are little anticipated in assessment studies (Cadiou et al. 2023 ) while they appear to influence the agri-environmental effects of AD to varying degrees. These results suggest that AD sustainable development needs to involve more specific support for agricultural situations, and for the territorial context in which anaerobic digestion is being developed. By understanding the farmer's rationality, farming advisory services could play a major role in the sustainable development of biogas plants. 4.2. The environmental impacts on the farms surveyed vary considerably. Assessed against the scientific literature, this diversity of practices shows that the agri-environmental balance of AD can vary greatly from farm to farm. There is a large volume of literature on energy cover crops and their benefits and risks for the agri-environment (Beillouin et al. 2021 ; Launay 2023 ). Cover cropping can have positive impacts on plot biodiversity, soil fertility, soil carbon storage and diseases, as well as weed and pest management. It can also lead to negatives such as reduced groundwater recharge and the need for increased nitrogen inputs. First, we have shown that although ECC was a common option for supplying the AD units, not all farmers decided to develop this crop on their farms. Among the farmers that cultivate ECC, they have adopted a diversity of practices (fertilization, species choice, acreage). We have identified two trends in crop rotation evolution, which have already been described in some empirical studies. The first trend is the development of winter energy crops in double cropping systems as observed in other French region (Carton and Levavasseur 2022 ), and as promoted in other countries like Austria (Szerencsits et al. 2015 ). These cropping systems have advantages in terms of soil cover and can help store more carbon in the soil (Launay et al. 2020 ; Carton and Levavasseur 2022 ; Malet 2022 ). However, the choice of ECC species can lead to a reduction in the diversity of crops with an increase in the proportion of grasses (Carton and Levavasseur 2022 ). In addition, ECC require additional water, which for some farmers means a drop in the yield of the main crop that follows (Launay et al. 2022 ). Ultimately, the magnitude of these effects will depend on a farmer’s technical management skills, the acreage concerned (see Table 3 ) and production objectives. The second trend is the development of maize, which is an excellent crop in terms of energy produced per hectare, whose area is frequently increasing in regions where biogas plants are being developed (Herrmann 2013 ; Lüker-Jans et al. 2017 ; Vergara and Lakes 2019 ; Ruf et al. 2021 ; Levavasseur et al. 2023 ). According to our 2021 surveys, maize is an economically attractive crop for AD in France, however, the increase in maize acreage is much less than that observed in Germany. In any case, conventional maize growing in the studied regions has no major agri-environmental benefit and tends to perpetuate conventional cultivation practices with synthetic input use, as also shown in the Ile-de-France region by Carton and Levavasseur ( 2022 ). However, we have also shown that some farmers make major changes to their crop rotations in relation to their conversion to organic farming. In this case, AD is a driver of legume reintroduction, it reduces the use of pesticides and brings diversification to the rotation. Outside of organic farming, on the surveyed farms, AD does not appear to be a direct lever of legume reintroduction through cover crops. Some technical and scientific literature on (energy) cover crops assess the value of choosing legumes to improve farm GHG balance (Stinner 2015 ) and nitrogen management (Stinner et al. 2018 ). (Marsac et al. 2019 ) have also shown that a legume association (up to 40%) with cereal is possible with no yield loss for the cover crop. But we have not observed the drivers for the development of these practices. The cultivation practices and evolution pathways of the farms studied are related to diverse environmental impacts and benefits. The “best practices” with regard to the cultivation of cover crops, which allow crop diversification and the reintroduction of legumes, are not often implemented, as a farmer’s strategy may involve the selection of other practices. The literature on digestate documents the benefits and technical conditions of optimized fertilization. Optimized nitrogen fertilization means optimizing chemical and physical fertility and minimizing nutrient losses to water and air. Therefore, in addition to the substitution of synthetic nitrogen, good spreading practices include: application according to the needs of the crop (at the end of winter and in spring for cereals and oilseed rape, before planting or during the first six to eight weeks for maize); equipment that limits nitrogen volatilization (using a dribble bar and burying digestate immediately after spreading); limiting compaction (monitoring the weight of the tank, using remote inflation, “tank-free” spreading) (Lukehurst et al. 2010 ; Severin et al. 2016 ; Nicholson et al. 2017 , 2018 ; Carton and Bulcke 2021 ). In the literature, agri-environmental assessments of biogas plants are often carried out on the assumption that these conditions are met (Vaneeckhaute et al. 2018 ; Grillo et al. 2021 ; Moinard 2021 ; Esnouf et al. 2021 ; Cadiou et al. 2023 ; Caquet et al. 2024 ). However, we have shown that these conditions are not always met, and sometimes cannot be met by farmers. Varying responses to spreading constraints lead to a diversity of fertilization practices and different ways of implementing recommended practices to optimize the use of digestate. The obstacles mentioned by the farmers (insufficient soil bearing capacity, cost of spreading equipment, work schedule burden) lead to varying degrees of substitutions of mineral nitrogen with digestate, ranging from very low substitution to total replacement of the mineral nitrogen consumed. These results testify to the possible discrepancies between practical implementation and theoretical "optimized" projections. From an environmental perspective, if digestate feedstocks are not used to replace synthetic nitrogen, then a farm will develop a nitrogen surplus, which increases the pollution risk (group 1). Conversely, reductions in the purchase of mineral N, being replaced by digestate fertilization for crops (group 2: farms with reductions of between 30% and 60%), improve the agri-environmental balance of farms. On these farms, the digestion of agro-industrial feedstocks and bio-waste offers an opportunity to establish a circular economy. However, easy access to external feedstocks rich in organic nitrogen could hinder the reintroduction of nitrogen-fixing plants into rotations. The combination of organic farming and anaerobic digestion (farms with savings between − 70% et -100%) may help to promote nitrogen circularity if the farm manages to complete its nitrogen cycle. Organic conversion appears to be a strong driver for the reintroduction of legumes, to lengthen the rotation and manage weed populations. However, the farms we surveyed also show that two out of three organic farmers base their production on the import of external nitrogen. As (Dumont et al. 2020 ) and (Nowak et al. 2015 ) have shown, assessing the sustainability of these systems requires quantifying the dependence of organic farming on conventional farming. Regarding soil fertility, spreading digestate in spring can increase the risk of soil compaction, as it tends to increase machinery traffic on crops and grasslands, as well as the weight of this machinery. Soil compaction affects the ecological functioning of soil (Keller and Or 2022 ), reduces fertilizer efficiency and yield (Meynard et al. 1981 ) and increases denitrification processes and N 2 O emissions (Sitaula et al. 2000 ). The issue of soil compaction is still poorly addressed empirically in the literature, but our qualitative results are consistent with the few modelling works on the subject (Ruf et al. 2021 ). In addition, we show that these compaction risks can vary greatly from one farmer to another, depending on whether they are able to invest in certain technical solutions (tank-free spreader, "low-pressure" tyres, decompaction tools) recommended in the literature (Carton and Bulcke 2021 ). The literature on the impacts of AD on permanent grassland is poor in France and in Europe. In Germany, Lupp et al. ( 2014 ) showed that under AD development - and under the policy framework of the time - the need for biomass and increased grassland yields can lead farmers to plough permanent grasslands. The ploughing of permanent grassland in connection with AD has not been shown to be a significant phenomenon in France at the national level (Levavasseur et al. 2023 ), but our results show that this situation does occur, driven by the same reasons as in Germany. Since 2013, grassland ploughing has been subject to regulation at the European level (European Parliament and Council 2013 ). This regulation is linked to unfavourable consequences resulting from land conversions for biodiversity and soil carbon storage (Tang et al. 2020 ). In France, one argument for developing AD is that it could support the maintenance of permanent grassland (and all of its environmental benefits on biodiversity and carbon storage): in a context of decreasing livestock, the digestion of grass could economically justify grassland conservation (Couturier et al. 2016 ). However, this mechanism has not been empirically assessed and should be the subject of further study. We have also observed an intensification in the management of permanent grasslands on most livestock farms. The increase in digestate fertilization can stimulate grass production. This grassland intensification, by promoting farm protein autonomy, can lower the consumption of animal concentrates. Indirectly it can also improve the GHG balance of feed since animal concentrates have a poor carbon footprint (Boerema et al. 2016 ). But this intensification in fertilization can also lead to a reduction of species biodiversity (Plantureux et al. 2005 ; Pärtel et al. 2015). Here again, we can see that AD development on farms can stimulate a variety of impacts, most of which are poorly documented. Our sample is not representative of the diversity of French farms that have adopted AD, but it shows that the environmental impacts of AD can be far more diverse than has been documented and assessed to date. According to the scientific literature, technically speaking, AD can be compatible with sustainable agriculture in terms of a range of issues (sustainable nitrogen management, greenhouse gases, soil carbon storage), however, as we have shown, the necessary conditions to attain the best environmental balance are not always met. These results converge with other empirical studies in France (SOLAGRO et al. 2018; Carton and Levavasseur 2022 ). So we can assume that the environmental impact of AD depends more on the pre-existing practices, production factors and the norms of the farming systems in which AD is developed, rather than on the AD technology itself (Markard et al. 2016 ; Cadiou 2023 ). AD thus appears to be an innovation compatible with the intensive farming regime that dominates in France for arable crops. This regime is characterized by the pursuit of high yields, is specialized in a small number of species, and relies heavily on synthetic inputs (Guichard et al. 2017 ; Meynard et al. 2018 ). But AD also appears compatible with organic farming, which represents a form of sustainable agriculture. This raises the question of the right socio-technical and socio-political conditions for the sustainable development of AD. 4.3 Assessing the sustainability of practices must consider the dynamics of farming systems and the agency of farmers. We have therefore shown that AD can induce a diversity of mechanisms on farms, leading to a range of agri-environmental impacts. The Farming system research framework is a good way of grasping the effects of AD on farming practices, moving away from a technical approach that focuses on the direct benefits and risks of AD technology. This research framework takes into consideration the interactions between practices, and therefore enables us to highlight issues that have been little addressed, such as the impacts of digestate fertilization on grassland biodiversity. It also accounts for different AD management strategies that lead to different impacts, which can be developed depending on the agency of the farmer. Conducting an impact assessment approach therefore requires 1/ documenting the actual practices of farmers in terms of managing AD feedstock and digestate; 2/ documenting the impacts of AD on other farm activities, and even on neighboring farms; and 3/ assessing their agri-environmental implications based on a battery of indicators chosen according to the evaluators' expectations, as for example the IDEA (Zahm et al. 2018 ). These sustainability indicators must be adapted to the new practices developed by farmers. During these three phases, particular attention must be paid to systemic changes, which may involve more virtuous or less virtuous practices overall (Byerlee et al. 1982 ; Doré et al. 1997 ). To make this kind of assessment more actionable, for example to support public policy making or farming advisory services, then such assessments could be supplemented by an analysis of the underlying logic behind farm changes. This approach can be developed by mobilizing the tools of agronomic diagnosis that aim to reconstruct the complex direct and indirect links between practices and performance. Indicators can be used to identify agronomic, environmental, and economic benefits and risks, but they do not tell us how practices should evolve (Meynard and David 1992 ; Doré et al. 1997 ). Thus, an agronomic diagnosis would provide a better understanding of the role of biogas in maintaining or changing certain practices and the need to think about the transition of the farm to optimize the impacts associated with biogas. These principles could be the basis for new research on the AD sustainability, but could also support the assessment studies conducted by R&D organisms, such as Chambers of Agriculture or technical institutes. This would help to improve understanding of the levers and constraints that influence the way that AD can lead to sustainable changes in practices. 5. Conclusion Our results validate the hypothesis presented at the beginning of the article: the agri-environmental sustainability of AD depends on complex systemic effects farm-level effects, that influence changes in practices in different ways. Consequently, AD induces a diversity of impacts depending on the management strategies and characteristics of each farm. Agri-environmental impacts related to these indirect mechanisms remain insufficiently documented in the literature even though they can significantly modify the agri-environmental balance of AD. To better assess the impact of biogas on agriculture, our results should be complemented by empirical studies in other regions, which would enable us to better document this diversity and identify the most representative practices and impacts. We have identified the following three avenues for further research. First, farm dynamics are themselves caught up in territorial dynamics. AD farmer can establish links with regional stakeholders during the development of an AD project, as well as when managing the AD supply and digestate spreading. Documenting these interactions and how they influence the farmers’ practices would help us to better grasp the indirect determinants of anaerobic digestion's impacts. Second, several agri-environmental issues are still very poorly empirically documented such as soil biodiversity and soil compaction. Researching these dimensions would elucidate how to protect the fertility of soils in the future. Third, systemic assessments of the impacts of AD could form the basis for a renewal of biogas public policy. Considering these mechanisms will lead to a better understanding of the factors driving or hampering sustainable biogas in both energy and agri-environmental terms. Our results orient public action toward establishing the conditions for adopting best practices and developing more sustainable AD systems on farms. Declarations Conflicts of interest/Competing interests (include appropriate disclosures): All authors have no conflicts of interest to declare that are relevant to the content of this article, and disclose financial or non-financial interests that are directly or indirectly related to this study. Dr. Jean-Marc Meynard serves as an Editor for Agronomy for Sustainable Development, but was never involved in the assessment of this article. In accordance with indexing service guidelines, he is permitted to submit manuscripts to the journal. Ethics approval (include appropriate approvals or waivers): The study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki. Consent to participate (include appropriate statements): Informed consent has been obtained from all human participants involved in this study Consent for publication (include appropriate statements): Consent for publication has been obtained from all individuals whose data is included in this study. Funding: This work was supported by ADEME (French Agency for Ecological Transition); ANR (French National Agency for Research) [grant number ANR-10-LABX-14–01]; INRAE (France's National Research Institute for Agriculture, Food, and the Environment); IDDRI (Institute for Sustainable Development and International Relations) and the IdEx Université de Paris [ANR-18-IDEX-0001]. Authors' contributions (include appropriate statements): JC designed the research study, conducted investigation and data analysis and wrote the first draft of the manuscript. JMM contributed to the study design, provided guidance throughout the research process, supervised the study and analysis and revised the manuscript for important intellectual content. PMA contributed to the study design, supervised the study and critically reviewed the manuscript. All authors read and approved the final manuscript. Acknowledgments: The authors would like to thank the 23 farmers who devoted their time to our surveys. The authors would also like to thank all the people in the Grand Est region who helped facilitate our fieldwork and the conduct of the interviews. Declarations: Availability of data and material (see in section 13 below what is expected here): The datasets generated during and/or analyzed during the current study are not publicly available due to anonymization needs. Code availability (software application or custom code): Not applicable. 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GCB Bioenergy 15:630–641. https://doi.org/10.1111/gcbb.13042 Lukehurst CT, Frost P, Seadi TA (2010) Utilization of digestate from biogas plants as biofertiliser. https://task37.ieabioenergy.com/wp-content/uploads/sites/32/2022/02/Digestate_Brochure_Revised_12-2010.pdf . Accessed 9 Sep 2022 Lüker-Jans N, Simmering D, Otte A (2017) The impact of biogas plants on regional dynamics of permanent grassland and maize area—The example of Hesse, Germany (2005–2010). Agric Ecosyst Environ 241:24–38. https://doi.org/10.1016/j.agee.2017.02.023 Lupp G, Steinhäußer R, Starick A et al (2014) Forcing Germany’s renewable energy targets by increased energy crop production: A challenge for regulation to secure sustainable land use practices. Land Use Policy 36:296–306. https://doi.org/10.1016/j.landusepol.2013.08.012 Malet N (2022) Retour au sol ou méthanisation agricole: quelle est la stratégie de gestion de la biomasse la plus efficace pour atténuer les émissions de CO2 ? Markard J, Wirth S, Truffer B (2016) Institutional dynamics and technology legitimacy – A framework and a case study on biogas technology. Res Policy 45:330–344. https://doi.org/10.1016/j.respol.2015.10.009 Marsac S, Heredia M, Bazet M et al (2019) Optimisation de la mobilisation de CIVE pour la méthanisation dans les systèmes d’exploitation. Nicolas Delaye, Robert Trochard, Hélène Lagrange, Caroline Quod, Eve-Anna Sanner. https://librairie.ademe.fr/cadic/4557/opticive_optimisation_methanisation__cive_rapport.pdf . Accessed 9 Sep 2022 Meynard J-M, Boiffin J, Caneill J, Sebillotte M (1981) Elaboration du rendement et fertilisation azotée du blé d’hiver en Champagne crayeuse II. - Types de réponse à la fumure azotée et application de la méthode du bilan prévisionnel. Agronomie 1:795–806. https://doi.org/10.1051/agro:19810912 Meynard J-M, Charrier F, Fares M et al (2018) Socio-technical lock-in hinders crop diversification in France. Agron Sustain Dev 38. https://doi.org/10.1007/s13593-018-0535-1 Meynard J-M, David G (1992) Diagnostic de l’élaboration du rendement des cultures. Cah Agric 1(1):9–19 Meynard J-M, Doré T, Habib R (2001) L’évaluation et la conception de systèmes de culture pour une agriculture durable. Comptes Rendus Académie Agric Fr 87:223–236 Moinard V (2021) Conséquences de l’introduction de la méthanisation dans une exploitation de polyculture-élevage sur les cycles du carbone et de l’azote. Combinaison de l’expérimentation et de la modélisation à l’échelle de la ferme Möller K (2015) Effects of anaerobic digestion on soil carbon and nitrogen turnover, N emissions, and soil biological activity. A review. Agron Sustain Dev 35:1021–1041. https://doi.org/10.1007/s13593-015-0284-3 Nicholson F, Bhogal A, Cardenas L et al (2017) Nitrogen losses to the environment following food based digestate and compost applications to agricultural land. Environ Pollut 228:504–516. https://doi.org/10.1016/j.envpol.2017.05.023 Nicholson F, Bhogal A, Rollett A et al (2018) Precision application techniques reduce ammonia emissions following food based digestate applications to grassland. Nutr Cycl Agroecosystems 110:151–159. https://doi.org/10.1007/s10705-017-9884-4 Nkoa R (2014) Agricultural benefits and environmental risks of soil fertilization with anaerobic digestates: a review. Agron Sustain Dev 34:473–492. https://doi.org/10.1007/s13593-013-0196-z Nowak B, Nesme T, David C, Pellerin S (2015) Nutrient recycling in organic farming is related to diversity in farm types at the local level. Agric Ecosyst Environ 204:17–26. https://doi.org/10.1016/j.agee.2015.02.010 Osty P-L, Lardon S, de Sainte-Marie C (1998) Comment analyser les transformations de l’activité productrice des agriculteurs ? Propositions à partir des systèmes techniques de production. Études Rech Sur Systèmes Agraires Dév 397–413 Paolini V, Petracchini F, Segreto M et al (2018) Environmental impact of biogas: A short review of current knowledge. J Environ Sci Health Part A 53:899–906. https://doi.org/10.1080/10934529.2018.1459076 Pärtel B, Sammul (2015) Biodiversity in temperate European grasslands: origin and conservation. Grasslande Sciences in Europe Plantureux S, Peeters A, McCracken D (2005) Biodiversity in intensive grasslands: Effect of management, improvement and challenges. Agron Res 3:153–164 Purswani J, Llorente CP (2021) Nitrification and Denitrification Processes: Environmental Impacts. In: Nitrogen Cycle. CRC Quakernack R, Pacholski A, Techow A et al (2012) Ammonia volatilization and yield response of energy crops after fertilization with biogas residues in a coastal marsh of Northern Germany. Agric Ecosyst Environ 160:66–74. https://doi.org/10.1016/j.agee.2011.05.030 Räbiger T, Andres M, Hegewald H et al (2020) Indirect nitrous oxide emissions from oilseed rape cropping systems by NH3 volatilization and nitrate leaching as affected by nitrogen source, N rate and site conditions. Eur J Agron 116:126039. https://doi.org/10.1016/j.eja.2020.126039 Ruf T, Gilcher M, Udelhoven T, Emmerling C (2021) Implications of Bioenergy Cropping for Soil: Remote Sensing Identification of Silage Maize Cultivation and Risk Assessment Concerning Soil Erosion and Compaction. Land 10:128. https://doi.org/10.3390/land10020128 Sadet-Bourgeteau S, Maron P-A, Dijon A, Rev (2020) AES 10 – 1 Agronomie et méthanisation:4 Sebillotte M (1974) Agronomie et agriculture: essai d’analyse des tâches de l’agronome. Série Biol 24:3–25 Severin M, Fuß R, Well R et al (2016) Greenhouse gas emissions after application of digestate: short-term effects of nitrification inhibitor and application technique effects. Arch Agron Soil Sci 62:1007–1020. https://doi.org/10.1080/03650340.2015.1110575 Siegmeier T, Blumenstein B, Möller D (2015) Farm biogas production in organic agriculture: System implications. Agric Syst 139:196–209. https://doi.org/10.1016/j.agsy.2015.07.006 Sitaula BK, Hansen S, Sitaula JIB, Bakken LR (2000) Effects of soil compaction on N2O emission in agricultural soil. Chemosphere - Glob Change Sci 2:367–371. https://doi.org/10.1016/S1465-9972(00)00040-4 Solagro (2018) Expertise Agronomique: Résultats de MethaLAE. https://solagro.org/travaux-et-productions/references/methalae-comment-la-methanisation-peut-etre-un-levier-pour-lagroecologie . Accessed 9 Oct 2023 – SOLAGRO et al (2018) AILE, TRAME, La méthanisation, levier de l’agroécologie ? In: Solagro. https://solagro.org/travaux-et-productions/references/methalae-comment-la-methanisation-peut-etre-un-levier-pour-lagroecologie . Accessed 18 Sep 2023 Stinner PW (2015) The use of legumes as a biogas substrate - potentials for saving energy and reducing greenhouse gas emissions through symbiotic nitrogen fixation. Energy Sustain Soc 5:4. https://doi.org/10.1186/s13705-015-0034-z Stinner PW, Deuker A, Schmalfuß T et al (2018) Perennial and Intercrop Legumes as Energy Crops for Biogas Production. In: Meena RS, Das A, Yadav GS, Lal R (eds) Legumes for Soil Health and Sustainable Management. Springer, Singapore, pp 139–171 Szerencsits M, Weinberger C, Kuderna M et al (2015) Biogas from Cover Crops and Field Residues: Effects on Soil, Water, Climate and Ecological Footprint. Int J Environ Ecol Eng 9:4. https://doi.org/10.5281/zenodo.1126493 Tang Y, Luo L, Carswell A et al (2020) Changes in soil organic carbon status and microbial community structure following biogas slurry application in a wheat-rice rotation. Sci Total Environ. https://doi.org/10.1016/j.scitotenv.2020.143786 Toffolini Q, Jeuffroy M-H, Mischler P et al (2017) Farmers’ use of fundamental knowledge to re-design their cropping systems: situated contextualisation processes. NJAS Wagening J Life Sci 80:37–47. https://doi.org/10.1016/j.njas.2016.11.004 van Midden C, Harris J, Shaw L et al (2023) The impact of anaerobic digestate on soil life: A review. Appl Soil Ecol 191:105066. https://doi.org/10.1016/j.apsoil.2023.105066 Vaneeckhaute C, Styles D, Prade T et al (2018) Closing nutrient loops through decentralized anaerobic digestion of organic residues in agricultural regions: A multi-dimensional sustainability assessment. Resour Conserv Recycl 136:110–117. https://doi.org/10.1016/j.resconrec.2018.03.027 Vergara F, Lakes T (2019) Maizification of the Landscape for Biogas Production? Humboldt. https://doi.org/10.18452/20977 . -Univ Zu Berl Wangel J (2011) Exploring social structures and agency in backcasting studies for sustainable development. Technol Forecast Soc Change 78:872–882. https://doi.org/10.1016/j.techfore.2011.03.007 Zahm F, Ugaglia AA, Barbier J-M, Boureau H (2018) Evaluating sustainability of farms: introducing a new conceptual framework based on three dimensions and five key properties relating to the sustainability of agriculture. The IDEA method version 4. 13th Eur IFSA Symp Farming Syst Facing Uncertainties Enhancing Oppor 20 Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 21 Nov, 2024 Reviewers invited by journal 20 Nov, 2024 Editor invited by journal 17 Oct, 2024 Editor assigned by journal 08 Oct, 2024 First submitted to journal 07 Oct, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5219576","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":380568881,"identity":"e2ad35cb-abab-43de-bb6e-e555e1df02fe","order_by":0,"name":"Jeanne Cadiou","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0001-8928-0640","institution":"","correspondingAuthor":true,"prefix":"","firstName":"Jeanne","middleName":"","lastName":"Cadiou","suffix":""},{"id":380568882,"identity":"fb15090a-8b7c-436b-990f-7f27858dc2f6","order_by":1,"name":"Jean-Marc Meynard","email":"","orcid":"https://orcid.org/0000-0002-4280-1768","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Jean-Marc","middleName":"","lastName":"Meynard","suffix":""},{"id":380568883,"identity":"445d3445-e645-49f2-948e-5f2494f4a4cf","order_by":2,"name":"Aubert Pierre-Marie","email":"","orcid":"https://orcid.org/0000-0002-0177-8127","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Aubert","middleName":"","lastName":"Pierre-Marie","suffix":""}],"badges":[],"createdAt":"2024-10-07 16:15:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5219576/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5219576/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70471490,"identity":"f0c2c8f8-9339-45f4-adf1-3e7359f5635b","added_by":"auto","created_at":"2024-12-03 13:27:19","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":337880,"visible":true,"origin":"","legend":"\u003cp\u003eAD unit developed by a group of farmers in northeast France. Legend: This AD unit has been developed by a group of farmers to diversify their income and produce renewable gas. The production of biogas by farmers brings various changes in their farming systems. It raises new questions on how AD can influence the environmental balance of different farming systems. Photo credit: Jeanne Cadiou, June 2021.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-5219576/v1/7a1cf973ac5949512d42fc29.jpeg"},{"id":70471724,"identity":"3945255b-7ca5-474f-bb36-920d5d43497b","added_by":"auto","created_at":"2024-12-03 13:35:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1276541,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5219576/v1/51b818cb-23b3-45da-99a3-e30af3c13062.pdf"}],"financialInterests":"","formattedTitle":"Accounting for systemic effects of anaerobic digestion development on farmers’ practices: implications for environmental assessment","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eSince the beginning of the 21st century, biogas produced from anaerobic digestion (AD) has developed around the world. Biogas production is mainly supported for its contribution to the energy transition, as a renewable decarbonized gas.\u003c/p\u003e \u003cp\u003eThe environmental impacts of AD vary greatly from one country to another, according to the feedstock digested (crops, manure, agricultural residues, biowaste), the technical options (AD unit technology, digestate management practices) and the magnitude of its development. In Europe, Germany is an example of high AD development: it has facilitated an increased in decarbonized electricity production, but at the same time, has seen negative impacts on biodiversity (Vergara and Lakes \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) and food prices (Britz and Delzeit \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). In France, AD was developed in agriculture (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) with the aim of avoiding the negative agri-environmental impacts observed in Germany. French biogas policy has even supported biogas production for its contribution to sustainable agriculture.\u003c/p\u003e \u003cp\u003eThe current environmental balance of biogas in France is under debate, and the scientific literature has failed to draw clear conclusions on its agri-environmental impacts (Moinard \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Malet \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Cadiou et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In this paper, we identify two main categories of studies that address this issue. The first category, which is the larger of the two, focuses on one or more of the agri-environmental effects of on-farm biogas development (mainly greenhouse gas balance, biodiversity, carbon storage, and nitrogen losses), assuming that the farming system as a whole remains unchanged. The literature in this category tends to assess direct changes limited to a few agricultural practices (Quakernack et al. \u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; M\u0026ouml;ller \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Bacenetti et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Nicholson et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Paolini et al. \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Greenberg et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Launay et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Esnouf et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), such as new methods of digestate fertilization, the introduction of energy cover crops, and manure digestion. Although these assessments analyse a range of different practices, they do not consider the systemic interactions between them. In general, the literature in this category assumes that farmers adopt the \u0026ldquo;best practices\u0026rdquo; recommended by agronomists (Cadiou et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and that certain agri-environmental effects are rather consensual. For example, the view may be expressed that adopting best practices will improve the greenhouse gas (GHG) balance, which can bring climate benefits (Hijazi et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Bacenetti et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Ingrao et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Malet \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2022\u003c/span\u003e); or that increased use of digestate fertilizer decreases the need for synthetic nitrogen, if the best spreading practices are adopted (Clements et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Nkoa \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Koszel and Lorencowicz \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Guilayn et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Without the adoption of best practices, increased use of digestate could increase the risk of air (Nkoa \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Carton and Bulcke \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Moinard \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and water pollution (M\u0026ouml;ller \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Nicholson et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; R\u0026auml;biger et al. \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Purswani and Llorente \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Other issues lack consensus or are even the subject of contradictory conclusions, such as the effects of digestate on soil carbon, which depends considerably on return-to-soil practices (Moinard \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Finally, the literature in this category contains much uncertainty on some issues, because the long-term perspective remains poorly documented, such as the impacts of digestate spreading on soil biology (Sadet-Bourgeteau et al. \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; van Midden et al. \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) and the impacts of AD on soil compaction and regional biodiversity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe second category of literature, which is much smaller, identifies indirect mechanisms that can influence the adoption of practices, highlighting that, as well as direct change, the development of AD on farms sometimes triggers changes in practices in other farm activities. Thus Beausang et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) show that the sustainability of grass silage used as an AD feedstock, depends on whether it indirectly displaces feed for livestock elsewhere. Carton \u0026amp; Levavasseur (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) show that soil carbon storage and biodiversity vary from one farm to another, on the introduction of energy cover crops to supply the AD unit. In Germany, Blumenstein et al. (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and Siegmeier et al. (\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) show, through qualitative modelling, that in some AD farms, higher crop yields and improved nitrogen management are coupled with a reducing labor and less energy costs. This body of research shows that the environmental performance of biogas can be related to other changes in the functioning of the farm or of the territory, even though few works really explore these links. Other papers show unexpected social, economic, and ecological outcomes. In Italy, an increase in a farm\u0026rsquo;s bioenergy crop production (Carrosio \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Cavicchi \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) or a territorial-level increase in the need for biomass as an AD feedstock can lead to increases in farmland rent, which in turn can influence agricultural systems. In Germany, in the 2010s, AD development led to a huge increase in maize production, increased land prices, and increased food prices (L\u0026uuml;ker-Jans et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Vergara and Lakes \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Based on these two categories of literature, it is difficult to draw clear conclusions on the environmental impacts of on-farm biogas development. Very few studies empirically assess the impacts of AD looking at systemic mechanisms and their influence on several agri-environmental aspects. This article aims to contribute to the understanding of the real effects of AD on farming practices and therefore on the sustainability pathways of farms by answering the following two questions: \u003cem\u003ehow does on-farm AD development change farm practices?; and what are the related agri-environmental impacts?\u003c/em\u003e\u003c/p\u003e \u003cp\u003eTo this end, we mobilize the \u0026ldquo;farming system studies\u0026rdquo; framework, which assumes that a system approach is necessary to capture the reasoning that underlies practices and their evolution (Sebillotte \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e1974\u003c/span\u003e; Biggs \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1985\u003c/span\u003e). It considers the agricultural system through the interaction between three scales: technical systems (field scale), production systems (farm scale) and agricultural territory (landscape scale) (Darnhofer et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Cochet \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Technical systems include highly interconnected cropping, livestock and forage systems: changing a practice in one technical system often affects other practices within the system, and other systems (Meynard et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2001\u003c/span\u003e). This approach also enables us to understand the trade-offs between production factors (labour, land, expertise) on a farm, and how this influences technical systems. AD is a new farm technical system that can modify the existing links between and within other technical systems (cropping, livestock\u0026hellip;). Beyond the consideration of AD as a technical system, its development necessarily requires the allocation of production factors. This, in turn, has consequences on the overall functioning of the farming system (Cochet et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Such changes must be understood through \u0026ldquo;the meaning that actors give to [them]\u0026rdquo; (Darnhofer et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The concept of \u0026ldquo;situated rationality\u0026rdquo; puts farmer strategies at the heart of the evolution of farming systems, viewing them as stakeholders and drivers of the emergence of new forms of sociotechnical organization (Osty et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e1998\u003c/span\u003e). This framework moves us away from an analysis of biogas development based on \u0026ldquo;rational modernization\u0026rdquo; and towards an understanding of the underlying \u0026ldquo;logic\u0026rdquo; of farmers, knowing that they may have conflicting goals. Finally, this article puts forward the following hypothesis: changes in practices associated with the management of AD units can be linked to indirect mechanisms involving other practices, other farm activities, and even regional dynamics, resulting in a much more diverse range of environmental impacts than the effects generally documented in the literature.\u003c/p\u003e"},{"header":"2. Material and Methods","content":"\u003cp\u003eWe surveyed 23 AD farmers in two French areas, Vosges and Bas-Rhin (northeast France) corresponding to 19 different on-farm AD units. The two areas differed in terms of (i) AD type (mostly combined heat and power (CHP) in Vosges, compared to biomethane injection in Bas-Rhin) and (ii) agricultural context (predominantly mixed farming in Vosges compared to more diversified production in Bas-Rhin, with field crops, mixed farming, market gardening, pigs and poultry). The aim was to cover a diversity of configurations based on the following criteria:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eActivity of the farm contacted (suckler, dairy, mixed farming, pig farming, cereals)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eNumber of AD unit project owners (individual, small or medium-sized collective)\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eInstalled capacity of the unit\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eEnergy recovery method (CHP or injection, and on-farm energy recovery activity)\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eWe tried to select the surveyed unit based on the digested feedstocks insofar as we were able to gather information on this criterion before the survey. We also selected biogas plants with a start-up date preferably before 2018, to gain perspective on farming systems changes.\u003c/p\u003e \u003cp\u003eThe choice of respondents therefore followed the \u0026ldquo;snowball sampling\u0026rdquo; method, to enable evolution in our field of investigation (Biernacki and Waldorf \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1981\u003c/span\u003e; Handcock and Gile \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2011\u003c/span\u003e): this approach involves making contact with an initial farmer, who then refers us to other farmers, from whom we get further referrals, and so on. In parallel, we gathered information on AD units and farms from technical publications, from AD unit websites, and from interviews with local stakeholders, to better select the farms surveyed according to our criteria. We stopped snowball sampling once we had covered a diverse range: in Vosges we surveyed 25% of the AD units in operation in 2021, and 50% in Bas-Rhin. Each farmer was interviewed for two to three hours, in two stages: a semi-structured interview in 2021, including a visit to the AD site, except for three farmers for whom the interview was conducted by phone; followed by a complementary semi-structured phone interview between January and June 2022. The author transcribed the interviews. Each farmer is designated by a letter.\u003c/p\u003e \u003cp\u003eInterviews began by gathering data on (i) current farming systems and the technical AD system; and (ii) the origin and history of the AD project. The interview then moved to a discussion of the ways in which AD had modified the farm, focusing on the following points:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eWhether or not the farming system, technical systems and practices had changed following the start of the AD project;\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe interactions between farming system components, and potentially the interactions between other regional variables/components (other farms, food industry);\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe rationale behind these changes, or the maintenance of previous practices.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cem\u003eCharacteristics of farms and AD units surveyed (from\u003c/em\u003e (Cadiou \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e)\u003cem\u003e). * It includes arable land and permanent grassland.\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRegion\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVosges\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eBas-Rhin\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003eNumber of farms for each agricultural activity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMulti-crop dairy\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMixed crop-livestock\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGrass-fed meat farming (sheep and cattle)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCereal\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMonogastric livestock\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eFarm area characteristics: average and [range of variation]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAverage total cultivated area* (ha)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e330 [80\u0026ndash;680]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e146 [40\u0026ndash;370]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAverage area of permanent grassland (ha)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e134 [25\u0026ndash;360]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e47 [0-150]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eNumber of farmers having invested in the AD unit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIndividual unit (N\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSmall collective unit (N\u0026thinsp;=\u0026thinsp;2)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMedium collective unit N = [4\u0026ndash;7]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eTotal number of AD units surveyed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eTotal number of AD farmers surveyed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYear of unit start-up\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInterval between the oldest unit and the most recent unit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e[2013\u0026ndash;2019]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e[2012\u0026ndash;2020]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eAverage installed capacity of units surveyed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCogeneration of heat and power (kW)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e404\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e542\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBiomethane injection (Nm3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e218\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiogas recovery method (cogeneration or injection)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNumber of cogeneration units out of total number of units\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 out of 10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5 out of 9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eWe analysed the data by looking for recurring examples of changes in practices (or lack of change) and of the drivers of the changes identified. In this way we have identified three main areas of technical change: crop rotations, fertilization, and forage and permanent grassland management. Data collected in the interviews on the description of practices were mainly qualitative and based on the observations of farmers. During the initial interviews, there was a back and forth with the literature to identify variables accessible to farmers, which enabled us to describe practices and to link them with agri-environmental effects based on the scientific literature. To characterize the sustainability of fertilization practices, we collected data on the digestate doses applied, the application calendar, application equipment, changes in mineral nitrogen fertilization, constraints, and levers for implementing good practices, and estimated nitrogen fertilizer savings on farms. Regarding the evolution of cropping systems, we collected data on crop succession, technical interventions (treatments, tillage), and the links between AD supply and crop rotation planning. Regarding forage management, we collected data on the evolution of forage cultivation (surface area, species, technical interventions) as well as on the established links between anaerobic digestion and livestock farming.\u003c/p\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Changes in crop rotations\u003c/h2\u003e \u003cp\u003eIn the two areas studied, AD is developing by valorizing livestock manure, supplemented by more methanogenic feedstock such as energy crops, cover crops, crop residues, biowaste and by-products (see Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Manure digestate is supported by French law, with a \u0026ldquo;manure\u0026rdquo; prime which gets to its maximum for a 60% manure supply or more.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSupply of surveyed AD plants (average percentage by volume of raw material according to feedstock category and ranges of variation in our sample).\u003c/p\u003e \u003cdiv class=\"Credit\"\u003e\u003cp\u003eSource: farmers.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAverage percentage [variation range] per area\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 Vosges units\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9 Bas-Rhin units\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAverage percentage of livestock manure\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e71% [35\u0026ndash;83%]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e66% [30\u0026ndash;90%]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAverage percentage of by-product (agricultural or agro-industrial) and biowaste\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8% [0\u0026ndash;16%]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e22% [5\u0026ndash;60%]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAverage percentage of energy crops\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12% [5\u0026ndash;45%]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4% [3\u0026ndash;17%]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAverage percentage of energy cover crops\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6% [4\u0026ndash;18%]\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7% [0\u0026ndash;42%]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThese differentiated supplies depend on the available feedstock in the area, which in turn influences strategies for changing cropping systems. We have identified four different patterns of change:\u003c/p\u003e \u003cp\u003e \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003ePattern 1: Maintaining previous crops and marginal changes to the cropping system (two farmers)\u003c/span\u003e. The initial rotation changed little, the introduction of new energy cover crops (ECC) for the AD plant remaining marginal. Q and R farmers have only modified their summer ECC for biogas production (maize, sorghum, or mixed crops), as they didn\u0026rsquo;t want to affect the yields of their spring crops. But they did not rely on these summer ECC crops to supply the biogas plant, because of their low yields, due to summer drought. These farmers feed their AD unit with a diversified mix of feedstock harvested in the area: agricultural co-products (maize stover (R), livestock effluents (Q, R)), bio-waste (R), agro-industrial by-products (Q).\u003c/p\u003e \u003cp\u003e \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003ePattern 2: Maintaining previous crops and developing ECC (3 farmers).\u003c/span\u003e The farmers (J, O, T) have chosen to produce more biomass via winter or summer ECC, for biogas production, without however modifying the succession of main crops: T and J cover their soils extensively in winter with rye and ryegrass (80ha and 40ha respectively at J), while farmer O has introduced around 20 ha of winter CIVE, and has increased his summer ECC area further - even though it is not very productive. The most methanogenic feedstocks come in part from off-farm purchases, such as bio-waste (O) and agro-industrial co-products (J, O, T), which are supplemented by winter CIVE.\u003c/p\u003e \u003cp\u003e \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003ePattern 3: Modification of the cropping system to contribute to biogas production by introducing energy crops and ECC (12 farmers).\u003c/span\u003e Most farmers have modified their rotations to introduce energy and ECC to supply the AD units. Eleven farmers have increased their area under maize silage, and two farmers have introduced a triticale and rye mix intercrop. These crops replace cash crops, mostly cereals (A, C, E, H, I, V), but also rapeseed (B, G), and grain maize (K, L, M, S, V) (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). As in pattern 2, farmers have introduced ECC either between their main crops or following energy crops. Most farmers chose winter ECC (rye, triticale, meslin) or temporary ryegrass-type meadows (A, B, C, E, G, H, I, M, S, V, W), which are methanogenic, and whose production per hectare is regarded as good (A, B, E, G, H, M, S, V, W). Compared with pattern 2, some farmers have accepted that double cropping affects maize yield (main crop) because the average net margin per hectare is better from their point of view (B, C, G, H, I, S, V, W). Others have preferred not to grow a double crop including maize, as the double crop affects the maize yield too much (A, E, L), so they have switched to an energy winter crop that is maintained on the field for longer: therefore, growing a winter rye followed by a temporary grassland or a summer ECC (A, E). Growing these crops on their own ensures autonomy in supplying the AD unit and means that they are not dependent on the availability and price of feedstocks purchased locally.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eChanges in crop rotation for Pattern 3 farmers with the development of AD\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFarmer\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStopped cultivation\u0026hellip;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReplaced by\u0026hellip;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping (if concerned)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5\u0026ndash;6 ha of cereals\u003c/p\u003e \u003cp\u003e7\u0026ndash;8 ha of permanent grassland\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12\u0026ndash;14 ha of rye\u003c/p\u003e \u003cp\u003eFew ha of maize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping possible depending on the year and the plot\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u0026ndash;20 ha of rapeseed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15\u0026ndash;20 ha of maize\u003c/p\u003e \u003cp\u003e10\u0026ndash;15 ha of ryegrass (ECC)\u003c/p\u003e \u003cp\u003e50ha of summer ECC (mix of grasses and legumes)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping before maize\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 ha of barley\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20 ha of maize\u003c/p\u003e \u003cp\u003ePartial reintroduction of temporary grassland (alfalfa, clover)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping with yield loss on the following maize crop\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eE\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e30\u0026ndash;40 ha of cereals\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e40 ha of rye, followed by a three-year ryegrass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo double cropping because of the maize yield loss\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15 ha of rapeseed\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 ha of maize\u003c/p\u003e \u003cp\u003e65 ha of winter cover crops (15ha of rye, 50 ha of ryegrass)\u003c/p\u003e \u003cp\u003eFew ha of summer ECC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping before maize\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ex ha of permanent grassland\u003c/p\u003e \u003cp\u003e(25-x) ha of triticale and clover\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25 ha of maize/sorghum\u003c/p\u003e \u003cp\u003e25 ha of rye (ECC)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping with yield loss on the following maize crop\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4\u0026ndash;5 ha of permanent grassland\u003c/p\u003e \u003cp\u003e2ha of barley\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6\u0026ndash;7 ha of maize\u003c/p\u003e \u003cp\u003eFew ha of temporary grassland cover\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25 ha of permanent grassland\u003c/p\u003e \u003cp\u003e10ha of maize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u0026ndash;15 ha of alfalfa\u0026thinsp;+\u0026thinsp;10 ha of cash crops\u003c/p\u003e \u003cp\u003e10 ha of rye followed by clover temporary grassland\u003c/p\u003e \u003cp\u003eIncrease in summer ECC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15 ha of grain maize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 ha of silage maize\u003c/p\u003e \u003cp\u003eAdaptation of summer ECC species for biogas production\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eM\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 ha of grain maize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20 ha of silage maize\u003c/p\u003e \u003cp\u003e15ha of rye (ECC)\u003c/p\u003e \u003cp\u003eFew ha of ryegrass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eS\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10 ha of grain maize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10 ha of silage maize\u003c/p\u003e \u003cp\u003e20-30ha of rye or ryegrass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping with yield loss on the following maize crop\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eV\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVaries from year to year: a few ha of irrigated grain maize\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eVariable from year to year: a few ha of irrigated silage maize or sorghum, or other irrigated summer ECC\u003c/p\u003e \u003cp\u003eVarious surface of winter ECC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping only on conventional crops\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eW\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 ha of wheat and barley\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12 ha of triticale-rye\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDouble cropping with yield loss on the following maize crop\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003ePattern 4: A major transformation of the cropping system linked to the dynamics of the agricultural activity in which AD takes place (four farmers).\u003c/span\u003e For some farmers, the development of AD is associated with major changes in their production activities. Three farms converted to organic farming in connection with AD. By fertilizing their organic crops with digestate, these farmers have significantly increased their yields (close to conventional farming yields), enabling them to make significant economic gains.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003e \u003cem\u003e\u0026ldquo;We wondered about going organic at the same time. The Chamber of Agriculture told us that we were crazy, that we would never grow enough to feed the AD plant, but then after a year of operation (...) we said to ourselves, why not go organic, especially because the digestate solves the fertilizer problem. And we also said to ourselves, if a crop fails in organic farming, we'll still be able to make the AD plant work, we won't have any dry losses. So finally, the conversion went more smoothly\" (Farmer D)\u003c/em\u003e \u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eFarmer U chose to remain in conventional production but saw that AD opened an opportunity to transform his whole farming activity: he diversified by introducing new activities (AD unit, milk processing workshop) and changed his cropping system to supply AD and make his dairy farm more resilient.\u003c/p\u003e \u003cp\u003eAs part of these structural transformations, farmers have developed ECC cultivation in different ways. In organic arable farming, D opted for ECC followed by temporary grassland, as double cropping reduced maize yields too much (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, line 2). He also buys conventional maize silage to supply his AD unit. Farmer N has integrated ECC into his rotation, he is due to supply the collective unit (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, line 3). To do so, he has diversified his rotation from \u003cem\u003emaize//wheat and green manure crop//beet;\u003c/em\u003e to \u003cem\u003ewheat/\u003c/em\u003e\u003cb\u003erye (ECC)\u003c/b\u003e\u003cem\u003e//buckwheat/\u003c/em\u003e\u003cb\u003etriticale (ECC)\u003c/b\u003e\u003cem\u003e//temporary grassland with clover (one year) (\u003c/em\u003ewhere \u0026ldquo;/\u0026rdquo; denotes intra-annual succession and \u0026ldquo;//\u0026rdquo; is inter-annual succession). For F and U, the evolution of the rotation is more closely linked to changes in their livestock farming. Both farmers switched from maize-based animal feed to a grass-based diet (F, U) combined with a cessation of maize in the crop rotation. Farmer F did not introduce energy crops or ECC as he was already supplying his AD unit without difficulty: he has links with a biowaste processing company through which he has access to the biowaste and agro-industrial co-products market. Farmer U, on the other hand, has introduced meslin energy crops into his rotation. To increase his crop production (AD and cows), he ploughed up 10 ha of permanent grassland.\u003c/p\u003e \u003cp\u003eBeyond the individual characteristics of farmers, we can identify three drivers that influence the patterns of change:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eAccess and/or dependence on a market for methanogenic feedstocks.\u003c/b\u003e The farmers with the oldest AD units [beginning in 2012\u0026ndash;2016] stress the fact that the price of co-products and bio-waste has risen considerably in recent years. Eleven farmers mention that, eight years ago, they were able to obtain these products at low cost or even free of charge, whereas now they face ever-increasing prices. For example, in 2021 farmer E bought mustard by-products for \u0026euro;56/tonne, compared to \u0026euro;28/tonne in 2013. The calculation of the biogas generated from a feedstock is at the heart of the construction of the supply of biogas plants: faced with the rising price of by-products, farmers adopted various strategies and decided whether to buy by-products, and whether to produce crops on their farms. Farmer T, for example, explained that to keep costs under control, he shifted his AD supply away from co-products and towards CIVE and energy crops (corn) \u0026ndash; which equates to a recent change from pattern 2 to pattern 3. Conversely, farmer R, who does not want to produce more crops on his farm, has tried to diversify his supply with biowaste, which is less expensive than co-products (pattern 1). These dynamics show the importance of the structuring of the territorial biomass market in the development of crop successions. We show that, depending on a farmer\u0026rsquo;s objectives and the market for feedstocks, this quest for feedstock autonomy opens up different rotation patterns - within the regulatory limit of a maximum of 15% energy crops in the supply.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eThe profitability requirement of the biogas plant.\u003c/b\u003e For farmers heavily dependent on ECC, the management of ECC is guided by the objective to produce as much biogas as possible. Since cultivating ECC requires more work than buying feedstock from outside the farm, it must be profitable. Farmers therefore often choose cereal (rye, triticale, meslin) for winter ECC and corn for summer ECC: which produces a lot of biomass. Among the farmers surveyed, two introduced legumes, marginally, via their summer (B) or winter (I) ECC. Reintroducing legumes does not serve their main objective, which is to produce as much biomass as possible.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eSynergy between organic farming and AD: a driver towards more diversified cropping systems.\u003c/b\u003e We observed synergies between AD and organic farming, involving the use of digestate as fertilizer. Among AD farmers who were converting to organic, this process leads to systemic changes in production systems, such as the lengthening and diversification of cropping systems. However, as two farmers demonstrated, the joint economic optimization of food and biogas production may rely on the purchase of non-organic crops from neighboring farmers (via biowaste for F, or via the purchase of manure and maize silage for D).\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Changes in fertilization practices\u003c/h2\u003e \u003cp\u003eFertilization practices have evolved with the start of AD for almost every farmer surveyed, since there is a need to manage digestate on their farms. P is the exception: as a mountain sheep farmer, it would not be feasible to spread digestate on his grassland. The way each farmer uses digestate influences to a greater or lesser extent his consumption of synthetic mineral nitrogen, depending on whether he replaces his mineral fertilizer applications with digestate.\u003c/p\u003e \u003cp\u003eA first group of six farmers do not reduce their use of synthetic fertilizer, or make only marginal reductions. They adopt the following practices: spreading digestate on crops before sowing corn, or when sowing cereals in autumn (E, H, Q, I), the remaining digestate is spread on grassland in autumn (C, E, K, I). There are three main reasons for the limited application of digestate to cereals in spring: (i) soils often have a low carrying capacity in spring, whereas spreading equipment is heavy (C, E, H, I, K, Q) and large volumes are needed to reach the necessary nitrogen supply for cereals; (ii) spreading takes a long time in spring (large volumes) (E, H, K); and (iii) farmers are concerned that spreading could damage seedlings that have just emerged (I). In autumn, on the other hand, there is a need to empty the slurry pit before winter, which leads to spreading at this time (E, K, H, I). New requirements for mineral nitrogen have also arisen on these farms, with the use of mineral nitrogen on crops destined for AD (E, H, I, K).\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003e \u003cem\u003e\"We don't want to spread at all in winter, so in October the tank has to be empty (...) because in spring we're not sure we'll be able to spread\u003c/em\u003e, \u003cb\u003eand\u003c/b\u003e \u003cem\u003ethen in spring I do all the fields that have a sufficient soil bearing capacity\" (Farmer C).\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eNine other farmers identify similar constraints influencing their practices (B, G, J, M, O, R, S, T, U). However, they are able to make bigger reductions in synthetic nitrogen use because of their willingness to spread digestate on winter wheat or barley in spring, whenever possible. Their success in this regard is linked to manpower, work schedules and spreading techniques (see below). Farmer U has been able to make even greater reductions in synthetic fertilizer use as a result of decreasing his milk production, and therefore adopting a spreading system that is sufficient for his low production objectives.\u003c/p\u003e \u003cp\u003eThe other four farmers (D, F, N, V) face similar spreading constraints but have significantly reduced their consumption of mineral nitrogen as they have partially or fully converted to organic farming.\u003c/p\u003e \u003cp\u003eThese different levels of reductions in nitrogen consumption are linked to the equipment and organization of spreading, that influence the speed of the spreading (characterized notably by the flow rate of the spreader and by the complexity to use the spreader) and the weight of the spreader, associated with risks of compaction.\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eEquipment and practices adopted due to \u0026ldquo;low resources\u0026rdquo;\u003c/b\u003e - Farmer I (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, column 2) decided to invest in a small slurry spreader (11 m3), because he could not afford a larger one, and its output is sufficient to spread on his small, grouped fields. Even though the spreader is light, nitrogen savings are limited because nozzle spreading can increase digestate nitrogen volatilization.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eEquipment and practices adopted to achieve \u0026ldquo;weight-rate compromise\" -\u003c/b\u003e farmers (B, C, E, F, H, K, L, M, N, Q, S, T, U, W) have sought a compromise between flow rate (hence working time and spreading efficiency) and equipment weight (risk of compaction). This choice is associated with a diversity of practices linked to personal objectives and resources: B, C, K, M, S and W spread in spring when they consider compaction risk to be limited; H and U practice minimum tillage to improve carrying capacity; B, C, H, K and L have invested in technical solutions to limit compaction (polypropylene tank, 3-axle tank, \"low-pressure\" tyres, decompaction tools); S increased site efficiency by transporting digestate to the field with a larger slurry tank (24 m\u003csup\u003e3\u003c/sup\u003e), and then spreading with a 18 m\u003csup\u003e3\u003c/sup\u003e tank. Farmer T has a self-propelled machine that enters the field without a tank, but which has storage for digestate that he fills up off the field. Farmers E and Q have opted for high throughput spreading (21 m\u003csup\u003e3\u003c/sup\u003e- 28 m\u003csup\u003e3\u003c/sup\u003e tank), with the aim of spreading large volumes of digestate and limiting spreading time. However, this practice limits the areas that can be spread in spring, and therefore also limits potential reductions in mineral fertilizer use. For these farmers, such practices result in a range of reductions in nitrogen fertilizer use (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, column 3). Other farmers, such as M, N and F consider that it is in their economic interest to spread at the optimum time for the crop, which is spring, even if this increases the risk of compaction. Overall, these practices can reduce mineral nitrogen use considerably (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, column 3, lines 3\u0026ndash;4).\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003e\u0026ldquo;Optimization of valorization\" practices -\u003c/b\u003e farmers D, G, J, O, R and V have sought to extend their spreading window by investing in slurry tanks of different sizes, and/or by combining slurry tank spreading with \"tank free\" spreading. Such tank-free equipment transports the digestate to the spreader via hoses, thus greatly reducing the weight in the field. This enables the extension of the spreading window, with less risk of compaction and plant mortality compared to spreading with a tank. As a result, these farmers save more on mineral fertilizers (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e, column 5). Most use service providers (A, G, J, O), as these operations are more complex and require more manpower and equipment than most farmers have. Over a certain field size, such equipment has a better throughput than equipment with a tank, but it is expensive. This system and equipment enable significant reductions in nitrogen fertilizer use, to a greater or lesser extent depending on the farm (last column of Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eThe different objectives of farmers, and their resources and constraints are therefore translated into a diversity of spreading practices, with various consequences in terms of reducing mineral nitrogen consumption.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eDiversity of relationships between fertilization practices and choice of spreading equipment and strategy. Farmer A is excluded from the classification as his fertilization system is too unstable to be analysed. Farmers L and W are included in the analysis, even though the recent and still incomplete implementation of certain practices suggests that these practices are likely to evolve in time. P is not included as he does not spread digestate on his farm.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSavings /spreading practices\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026ldquo;Low resource\u0026rdquo;\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u0026ldquo;Weight-rate compromise\"\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u0026ldquo;Optimization of valorization\"\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e0% or slight diminution\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eI\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC, E, H, K, L, Q, W\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSignificant decrease (between 30% and 60%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eB, M, S\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eG, J, O, R\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStrong decrease (Between 70% and 100%)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eF, N, U, T\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eD, V\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe choice of spreading equipment also includes the choice of techniques for depositing and/or burying digestate. In our surveys, all but one farmer used a dribble bar to limit ammonia volatilization; most bought this equipment when the AD was installed. The farmer (I) who did not invest in a dribble bar did so because he prefers smaller, less expensive equipment, even if it means losing nitrogen through volatilization. Two farmers spoke about problems with clogged pipes (W, H): H prefers to use splash plate spreading in winter, which avoids the risk of frozen digestate clogging the pipes. Eighteen out of 21 farmers, however, have no specific digestate burying equipment, because: (i) it is too expensive (nine farmers); (ii) it requires too much power, so would require reinvestment in a new tractor (ten farmers); (iii) it spreads over a smaller width, so would require more passes over the field (ten farmers); or (iv) it is not practical for spreading on grassland (S). Seven of these 18 farmers plough the digestate into the land quickly (just after or on the same day) when spreading before sowing by tilling (stubble cultivator, disc or harrow), to limit nitrogen losses. The work schedule may delay soil preparation, as in the case of farmer M, who harrows when he has available manpower. The last three farmers (C, Q, T) have invested in equipment that can tow a burying ramp and has a high work rate, with the goal of reducing nitrogen losses. All three had sufficient manpower to manage spreading and the economic capacity to invest in this equipment.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Changes in forage and permanent grasslands management\u003c/h2\u003e \u003cp\u003eWith the development of AD, six farmers (A, B, E, G, K, J) have decided to produce more fodder crops (maize, temporary meadows) and to stockpile more in anticipation of potential drought: these farmers report that if stockpiles are not used in livestock farming a last-resort economic outlet exists in AD. By guaranteeing a way to valorize plant biomass, AD gives these farmers greater flexibility in forage management.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003e \u003cem\u003e\"This year we made a rye-clover mixture to make a second-cut clover. Depending on forage stocks, the rye may or may not be used for AD\" (Farmer K).\u003c/em\u003e \u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eConversely, other farmers (B, C, H, J, M) used the crops planned for AD as animal feed. While other farmers (A, K, B, J, Q, R) considered that they could afford to buy external maize or other products for AD - which is less the case for livestock farming. They therefore prioritize the use of their own farm-grown crops for livestock production. Other farmers (K, O), due to repeated droughts and low ECC and corn production, buy corn silage to supplement their AD crops.\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003e \u003cem\u003e\"Initially intended for AD, the rye has been partly conserved for cows (5ha). The sorghum produced in 2022 will also be used primarily for cows, depending on needs. AD still requires the purchase of silage maize\" (Farmer M)\u003c/em\u003e \u003c/p\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eMore broadly, the arrival of AD is bringing about changes on farms that are influencing the management of permanent grasslands. In the Vosges and Bas-Rhin areas, farmers say that they fertilize permanent grasslands more than before AD. The farmers who significantly increased their grassland fertilization were those who had previously fertilized little (A, E, J, K, T, W) with slurry/manure, and had now started to fertilize with digestate. Other farmers who used to fertilize with mineral nitrogen (between 15 and 65kgN/ha) have also increased their fertilization (B, C, H, M, S). They fertilize more because the meadows are easily spreadable before winter, when the digestate pit must be emptied (see 3.2). This change in fertilization has resulted in an increase in grass yields, noted by 12 farmers, and consequently a change in grassland management and grass consumption strategies for some of these farmers:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eC and J now sell more grass.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eA, H, I and K have ploughed grassland areas to produce more cash crops, for livestock and for AD.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eA, B, C, D, I and K use their surplus grass from permanent grassland for AD, generally the 2nd and 3rd cuts, which are of poorer quality for cows.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eSome farmers (E, G, H, J) also use temporary grassland for AD.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003cp\u003eBehind these different changes in practices, we can identify two important drivers:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eCompetition or synergy between AD and livestock farming\u003c/b\u003e: The economic attractiveness of anaerobic digestion is a key factor in encouraging farmers to adopt AD. Seven farmers said that for the same amount of work, an AD unit is more profitable than livestock. Changes in forage management practices depend on the economic choices made by farmers around the adoption of these activities, and on the economic benefits delivered by AD. Some farmers have made livestock farming a priority: they emphasize their attachment to the livestock profession and a desire to maintain these activities, even if there would be greater economic benefit in prioritizing AD feeding (J, B, O). Some farmers were initially reluctant to use corn or other crops for AD, but ultimately decided to do so. Other farmers plan to prioritize AD over livestock farming or the production of cash crops (I, K), because of economic considerations. Other farmers have also made the financial decision to invest in AD instead of livestock: C and E have disposed of beef finishing units to devote more resources (fodder and labour) to AD.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003e \u003cb\u003eDigestate that can be used to intensify permanent grassland\u003c/b\u003e: AD introduces a new organic fertilizer to the farm that can easily be used on permanent grassland. As discussed in section 3.2, spring spreading constraints mean that autumn spreading on grassland is sometimes favoured by farmers, enabling them to intensify forage production. AD is therefore indirectly changing grassland management practices, the composition of animal feed and land use.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003ch2\u003e 4.1 Understanding changes in practices involves considering the agency of farmers and the dynamics of farming systems.\u003c/h2\u003e \u003cp\u003eAs discussed in the introduction, there has been little research into the influence of AD on farming practices that also consider the mechanisms of systemic changes at the farm level.\u003c/p\u003e \u003cp\u003eFirst, we showed that the evolution of the organization of farm activities plays a role in the development of a diversity of practices. These results are in line with the few studies that have highlighted that the creation of AD on a farm has a major influence on its socio-economic organization (Emmann et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Carrosio \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Grouiez et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The synergies or competition between livestock rearing and AD on forage management illustrate the importance of considering interactions between farm activities to assess AD impacts. Some mechanisms have been identified, such as the increase or loss of forage autonomy (Solagro \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), and the increase in animal husbandry (Carrosio \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), while structural synergies between AD and organic farming have already been studied in Germany (Siegmeier et al. \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Our empirical work also shows that digestate production on AD farms can facilitate the transition to organic farming. However, AD raises the question of closing the nitrogen cycle, an issue that is not tackled in the scientific literature. If an AD unit on an organic farm is fed at least in part by products from conventional farms, then the synergy between organic farming and AD depends indirectly on the use of mineral fertilizers on these conventional farms. These circumstances may not encourage the closing of the nitrogen cycle with the development of legume crops (as a main or cover crop). At the territorial level, to our knowledge there has been no research into the regional dynamics of AD development, and how this can influence farm practices. We show that the availability of methanogenic feedstock on the territory can influence the evolution of cropping systems. This result is in line with (Cadiou \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), who showed that a rapid increase in the number of AD units in a territory could create competition among farmers for access to feedstock (agro-industrial by-products, manure from surrounding farms, maize).\u003c/p\u003e \u003cp\u003eSecondly, regarding digestate spreading, we have shown that farm characteristics (field size, economic resources, farmer knowledge, manpower) make certain technical solutions either beneficial or feasible: the choice of spreading equipment and techniques depends on a multiplicity of factors linked to the farm, which are independent of the AD system. On this subject, our results converge with those of (Carton and Levavasseur \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and (Markard et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), and with the literature on farming system research (Ingram \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Toffolini et al. \u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), which show that choices of practices depend very much on a farmer\u0026rsquo;s previous knowledge and practices, and not only on the best available or recommended technical solutions. Farmers may also pursue diverse farm management objectives (maintenance of livestock, increased income, better allocation of work time etc.) that open up additional digestate management options. For example, some farmers view digestate as a cumbersome by-product that requires a lot of work, while for others (such as organic farmers), digestate is a new fertilization opportunity that offers economic gains and greater autonomy. As a result, the nitrogen in digestate would be used inefficiently by the former, while the latter would opt for practices that optimize nitrogen use. In this way, a better understanding of the agency of AD farmers can help identify the obstacles and levers to good practices. In fact, our results take issue with the hypotheses of economic rationality and technique optimization - which are established in the technology development literature\u003c/p\u003e \u003cp\u003e(Geels and Smith \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Wangel \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) \u0026ndash; by highlighting the importance of the diversity of situations faced by farmers and their motivations. Thus, considering the diversity of farms and the agency of farmers, we show that actual practices can be more varied than previously documented. These indirect mechanisms are little anticipated in assessment studies (Cadiou et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) while they appear to influence the agri-environmental effects of AD to varying degrees.\u003c/p\u003e \u003cp\u003eThese results suggest that AD sustainable development needs to involve more specific support for agricultural situations, and for the territorial context in which anaerobic digestion is being developed. By understanding the farmer's rationality, farming advisory services could play a major role in the sustainable development of biogas plants.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e4.2. The environmental impacts on the farms surveyed vary considerably.\u003c/h2\u003e \u003cp\u003eAssessed against the scientific literature, this diversity of practices shows that the agri-environmental balance of AD can vary greatly from farm to farm. There is a large volume of literature on energy cover crops and their benefits and risks for the agri-environment (Beillouin et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Launay \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Cover cropping can have positive impacts on plot biodiversity, soil fertility, soil carbon storage and diseases, as well as weed and pest management. It can also lead to negatives such as reduced groundwater recharge and the need for increased nitrogen inputs. First, we have shown that although ECC was a common option for supplying the AD units, not all farmers decided to develop this crop on their farms. Among the farmers that cultivate ECC, they have adopted a diversity of practices (fertilization, species choice, acreage). We have identified two trends in crop rotation evolution, which have already been described in some empirical studies. The first trend is the development of winter energy crops in double cropping systems as observed in other French region (Carton and Levavasseur \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), and as promoted in other countries like Austria (Szerencsits et al. \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). These cropping systems have advantages in terms of soil cover and can help store more carbon in the soil (Launay et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Carton and Levavasseur \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Malet \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, the choice of ECC species can lead to a reduction in the diversity of crops with an increase in the proportion of grasses (Carton and Levavasseur \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). In addition, ECC require additional water, which for some farmers means a drop in the yield of the main crop that follows (Launay et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Ultimately, the magnitude of these effects will depend on a farmer\u0026rsquo;s technical management skills, the acreage concerned (see Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and production objectives. The second trend is the development of maize, which is an excellent crop in terms of energy produced per hectare, whose area is frequently increasing in regions where biogas plants are being developed (Herrmann \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; L\u0026uuml;ker-Jans et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Vergara and Lakes \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ruf et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Levavasseur et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). According to our 2021 surveys, maize is an economically attractive crop for AD in France, however, the increase in maize acreage is much less than that observed in Germany. In any case, conventional maize growing in the studied regions has no major agri-environmental benefit and tends to perpetuate conventional cultivation practices with synthetic input use, as also shown in the Ile-de-France region by Carton and Levavasseur (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, we have also shown that some farmers make major changes to their crop rotations in relation to their conversion to organic farming. In this case, AD is a driver of legume reintroduction, it reduces the use of pesticides and brings diversification to the rotation. Outside of organic farming, on the surveyed farms, AD does not appear to be a direct lever of legume reintroduction through cover crops. Some technical and scientific literature on (energy) cover crops assess the value of choosing legumes to improve farm GHG balance (Stinner \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) and nitrogen management (Stinner et al. \u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). (Marsac et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) have also shown that a legume association (up to 40%) with cereal is possible with no yield loss for the cover crop. But we have not observed the drivers for the development of these practices. The cultivation practices and evolution pathways of the farms studied are related to diverse environmental impacts and benefits. The \u0026ldquo;best practices\u0026rdquo; with regard to the cultivation of cover crops, which allow crop diversification and the reintroduction of legumes, are not often implemented, as a farmer\u0026rsquo;s strategy may involve the selection of other practices.\u003c/p\u003e \u003cp\u003eThe literature on digestate documents the benefits and technical conditions of optimized fertilization. Optimized nitrogen fertilization means optimizing chemical and physical fertility and minimizing nutrient losses to water and air. Therefore, in addition to the substitution of synthetic nitrogen, good spreading practices include: application according to the needs of the crop (at the end of winter and in spring for cereals and oilseed rape, before planting or during the first six to eight weeks for maize); equipment that limits nitrogen volatilization (using a dribble bar and burying digestate immediately after spreading); limiting compaction (monitoring the weight of the tank, using remote inflation, \u0026ldquo;tank-free\u0026rdquo; spreading) (Lukehurst et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Severin et al. \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Nicholson et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Carton and Bulcke \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In the literature, agri-environmental assessments of biogas plants are often carried out on the assumption that these conditions are met (Vaneeckhaute et al. \u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Grillo et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Moinard \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Esnouf et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Cadiou et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Caquet et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, we have shown that these conditions are not always met, and sometimes cannot be met by farmers. Varying responses to spreading constraints lead to a diversity of fertilization practices and different ways of implementing recommended practices to optimize the use of digestate. The obstacles mentioned by the farmers (insufficient soil bearing capacity, cost of spreading equipment, work schedule burden) lead to varying degrees of substitutions of mineral nitrogen with digestate, ranging from very low substitution to total replacement of the mineral nitrogen consumed. These results testify to the possible discrepancies between practical implementation and theoretical \"optimized\" projections.\u003c/p\u003e \u003cp\u003eFrom an environmental perspective, if digestate feedstocks are not used to replace synthetic nitrogen, then a farm will develop a nitrogen surplus, which increases the pollution risk (group 1). Conversely, reductions in the purchase of mineral N, being replaced by digestate fertilization for crops (group 2: farms with reductions of between 30% and 60%), improve the agri-environmental balance of farms. On these farms, the digestion of agro-industrial feedstocks and bio-waste offers an opportunity to establish a circular economy. However, easy access to external feedstocks rich in organic nitrogen could hinder the reintroduction of nitrogen-fixing plants into rotations.\u003c/p\u003e \u003cp\u003eThe combination of organic farming and anaerobic digestion (farms with savings between \u0026minus;\u0026thinsp;70% et -100%) may help to promote nitrogen circularity if the farm manages to complete its nitrogen cycle. Organic conversion appears to be a strong driver for the reintroduction of legumes, to lengthen the rotation and manage weed populations. However, the farms we surveyed also show that two out of three organic farmers base their production on the import of external nitrogen. As (Dumont et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and (Nowak et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) have shown, assessing the sustainability of these systems requires quantifying the dependence of organic farming on conventional farming. Regarding soil fertility, spreading digestate in spring can increase the risk of soil compaction, as it tends to increase machinery traffic on crops and grasslands, as well as the weight of this machinery. Soil compaction affects the ecological functioning of soil (Keller and Or \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), reduces fertilizer efficiency and yield (Meynard et al. \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1981\u003c/span\u003e) and increases denitrification processes and N\u003csub\u003e2\u003c/sub\u003eO emissions (Sitaula et al. \u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). The issue of soil compaction is still poorly addressed empirically in the literature, but our qualitative results are consistent with the few modelling works on the subject (Ruf et al. \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In addition, we show that these compaction risks can vary greatly from one farmer to another, depending on whether they are able to invest in certain technical solutions (tank-free spreader, \"low-pressure\" tyres, decompaction tools) recommended in the literature (Carton and Bulcke \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe literature on the impacts of AD on permanent grassland is poor in France and in Europe. In Germany, Lupp et al. (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2014\u003c/span\u003e) showed that under AD development - and under the policy framework of the time - the need for biomass and increased grassland yields can lead farmers to plough permanent grasslands. The ploughing of permanent grassland in connection with AD has not been shown to be a significant phenomenon in France at the national level (Levavasseur et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), but our results show that this situation does occur, driven by the same reasons as in Germany. Since 2013, grassland ploughing has been subject to regulation at the European level (European Parliament and Council \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). This regulation is linked to unfavourable consequences resulting from land conversions for biodiversity and soil carbon storage (Tang et al. \u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn France, one argument for developing AD is that it could support the maintenance of permanent grassland (and all of its environmental benefits on biodiversity and carbon storage): in a context of decreasing livestock, the digestion of grass could economically justify grassland conservation (Couturier et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). However, this mechanism has not been empirically assessed and should be the subject of further study.\u003c/p\u003e \u003cp\u003eWe have also observed an intensification in the management of permanent grasslands on most livestock farms. The increase in digestate fertilization can stimulate grass production. This grassland intensification, by promoting farm protein autonomy, can lower the consumption of animal concentrates. Indirectly it can also improve the GHG balance of feed since animal concentrates have a poor carbon footprint (Boerema et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). But this intensification in fertilization can also lead to a reduction of species biodiversity (Plantureux et al. \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2005\u003c/span\u003e; P\u0026auml;rtel et al. 2015). Here again, we can see that AD development on farms can stimulate a variety of impacts, most of which are poorly documented.\u003c/p\u003e \u003cp\u003eOur sample is not representative of the diversity of French farms that have adopted AD, but it shows that the environmental impacts of AD can be far more diverse than has been documented and assessed to date. According to the scientific literature, technically speaking, AD can be compatible with sustainable agriculture in terms of a range of issues (sustainable nitrogen management, greenhouse gases, soil carbon storage), however, as we have shown, the necessary conditions to attain the best environmental balance are not always met. These results converge with other empirical studies in France (SOLAGRO et al. 2018; Carton and Levavasseur \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSo we can assume that the environmental impact of AD depends more on the pre-existing practices, production factors and the norms of the farming systems in which AD is developed, rather than on the AD technology itself (Markard et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Cadiou \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). AD thus appears to be an innovation compatible with the intensive farming regime that dominates in France for arable crops. This regime is characterized by the pursuit of high yields, is specialized in a small number of species, and relies heavily on synthetic inputs (Guichard et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Meynard et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). But AD also appears compatible with organic farming, which represents a form of sustainable agriculture. This raises the question of the right socio-technical and socio-political conditions for the sustainable development of AD.\u003c/p\u003e \u003ch2\u003e4.3 Assessing the sustainability of practices must consider the dynamics of farming systems and the agency of farmers.\u003c/h2\u003e \u003cp\u003eWe have therefore shown that AD can induce a diversity of mechanisms on farms, leading to a range of agri-environmental impacts. The Farming system research framework is a good way of grasping the effects of AD on farming practices, moving away from a technical approach that focuses on the direct benefits and risks of AD technology. This research framework takes into consideration the interactions between practices, and therefore enables us to highlight issues that have been little addressed, such as the impacts of digestate fertilization on grassland biodiversity. It also accounts for different AD management strategies that lead to different impacts, which can be developed depending on the agency of the farmer.\u003c/p\u003e \u003cp\u003eConducting an impact assessment approach therefore requires 1/ documenting the actual practices of farmers in terms of managing AD feedstock and digestate; 2/ documenting the impacts of AD on other farm activities, and even on neighboring farms; and 3/ assessing their agri-environmental implications based on a battery of indicators chosen according to the evaluators' expectations, as for example the IDEA (Zahm et al. \u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). These sustainability indicators must be adapted to the new practices developed by farmers. During these three phases, particular attention must be paid to systemic changes, which may involve more virtuous or less virtuous practices overall (Byerlee et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1982\u003c/span\u003e; Dor\u0026eacute; et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). To make this kind of assessment more actionable, for example to support public policy making or farming advisory services, then such assessments could be supplemented by an analysis of the underlying logic behind farm changes.\u003c/p\u003e \u003cp\u003eThis approach can be developed by mobilizing the tools of agronomic diagnosis that aim to reconstruct the complex direct and indirect links between practices and performance. Indicators can be used to identify agronomic, environmental, and economic benefits and risks, but they do not tell us how practices should evolve (Meynard and David \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Dor\u0026eacute; et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). Thus, an agronomic diagnosis would provide a better understanding of the role of biogas in maintaining or changing certain practices and the need to think about the transition of the farm to optimize the impacts associated with biogas.\u003c/p\u003e \u003cp\u003eThese principles could be the basis for new research on the AD sustainability, but could also support the assessment studies conducted by R\u0026amp;D organisms, such as Chambers of Agriculture or technical institutes. This would help to improve understanding of the levers and constraints that influence the way that AD can lead to sustainable changes in practices.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eOur results validate the hypothesis presented at the beginning of the article: the agri-environmental sustainability of AD depends on complex systemic effects farm-level effects, that influence changes in practices in different ways. Consequently, AD induces a diversity of impacts depending on the management strategies and characteristics of each farm. Agri-environmental impacts related to these indirect mechanisms remain insufficiently documented in the literature even though they can significantly modify the agri-environmental balance of AD. To better assess the impact of biogas on agriculture, our results should be complemented by empirical studies in other regions, which would enable us to better document this diversity and identify the most representative practices and impacts.\u003c/p\u003e \u003cp\u003eWe have identified the following three avenues for further research. First, farm dynamics are themselves caught up in territorial dynamics. AD farmer can establish links with regional stakeholders during the development of an AD project, as well as when managing the AD supply and digestate spreading. Documenting these interactions and how they influence the farmers\u0026rsquo; practices would help us to better grasp the indirect determinants of anaerobic digestion's impacts. Second, several agri-environmental issues are still very poorly empirically documented such as soil biodiversity and soil compaction. Researching these dimensions would elucidate how to protect the fertility of soils in the future. Third, systemic assessments of the impacts of AD could form the basis for a renewal of biogas public policy. Considering these mechanisms will lead to a better understanding of the factors driving or hampering sustainable biogas in both energy and agri-environmental terms. Our results orient public action toward establishing the conditions for adopting best practices and developing more sustainable AD systems on farms.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflicts of interest/Competing interests\u003c/h2\u003e \u003cp\u003e(include appropriate disclosures): All authors have no conflicts of interest to declare that are relevant to the content of this article, and disclose financial or non-financial interests that are directly or indirectly related to this study. Dr. Jean-Marc Meynard serves as an Editor for Agronomy for Sustainable Development, but was never involved in the assessment of this article. In accordance with indexing service guidelines, he is permitted to submit manuscripts to the journal.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eEthics approval\u003c/strong\u003e \u003cp\u003e(include appropriate approvals or waivers): The study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent to participate\u003c/strong\u003e \u003cp\u003e(include appropriate statements): Informed consent has been obtained from all human participants involved in this study\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003e(include appropriate statements): Consent for publication has been obtained from all individuals whose data is included in this study.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eThis work was supported by ADEME (French Agency for Ecological Transition); ANR (French National Agency for Research) [grant number ANR-10-LABX-14\u0026ndash;01]; INRAE (France's National Research Institute for Agriculture, Food, and the Environment); IDDRI (Institute for Sustainable Development and International Relations) and the IdEx Universit\u0026eacute; de Paris [ANR-18-IDEX-0001].\u003c/p\u003e\u003ch2\u003eAuthors' contributions\u003c/h2\u003e \u003cp\u003e(include appropriate statements): JC designed the research study, conducted investigation and data analysis and wrote the first draft of the manuscript. JMM contributed to the study design, provided guidance throughout the research process, supervised the study and analysis and revised the manuscript for important intellectual content. PMA contributed to the study design, supervised the study and critically reviewed the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgments:\u003c/h2\u003e \u003cp\u003eThe authors would like to thank the 23 farmers who devoted their time to our surveys. The authors would also like to thank all the people in the Grand Est region who helped facilitate our fieldwork and the conduct of the interviews.\u003c/p\u003e \u003cp\u003eDeclarations:\u003c/p\u003e\u003ch2\u003eAvailability of data and material\u003c/h2\u003e \u003cp\u003e(see in section 13 below what is expected here): The datasets generated during and/or analyzed during the current study are not publicly available due to anonymization needs.\u003c/p\u003e\u003ch2\u003eCode availability\u003c/h2\u003e \u003cp\u003e(software application or custom code): Not applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBacenetti J, Sala C, Fusi A, Fiala M (2016) Agricultural anaerobic digestion plants: What LCA studies pointed out and what can be done to make them more environmentally sustainable. 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The IDEA method version 4. 13th Eur IFSA Symp Farming Syst Facing Uncertainties Enhancing Oppor 20\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"agronomy-for-sustainable-development","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ASDE","sideBox":"Learn more about [Agronomy for Sustainable Development](https://www.springer.com/journal/13593)","snPcode":"13593","submissionUrl":"https://www2.cloud.editorialmanager.com/asde/default2.aspx","title":"Agronomy for Sustainable Development","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Biogas, sustainability, practices’ change, anaerobic digestion, systemic effects, diversity, farming system","lastPublishedDoi":"10.21203/rs.3.rs-5219576/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5219576/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOn-farm biogas production has been increasingly developing in Europe since the beginning of the twentieth century, mainly supported by energy policies. However, biogas production brings new challenges in agriculture, and it is difficult to draw clear conclusions on its agri-environmental effects from the current scientific literature. Current studies focus on one or more of the agri-environmental effects of on-farm biogas development (mainly greenhouse gas balance, carbon storage, and nitrogen losses), assuming that the farming system as a whole remains unchanged, but they rarely investigate how the performance of biogas relates to indirect changes in farm practices and activities.\u003c/p\u003e\n\u003cp\u003eTo better understand the changes in farm practices linked to biogas production, we surveyed 23 biogas farmers corresponding to 19 different on-farm biogas units in two areas of northeast France. We aimed to cover a diversity of configurations (e.g., of farm activities, installed biogas capacity, number of biogas farmers per project, and energy recovery methods) to capture a diversity of farm functioning. We analyzed these qualitative data by looking for recurring examples of changes in practices (or lack thereof) and drivers of the identified changes.\u003c/p\u003e\n\u003cp\u003eOur results show various changes in practices and drivers of change resulting in a much more diverse range of environmental impacts than those generally assessed in the literature. This diversity of impacts depends on both the farm characteristics and the different organizations of farm activities that biogas farmers can develop. Here we show that the necessary conditions to attain the best environmental balance are not always met, contrary to the common assumptions in the biogas assessment literature. On-farm biogas sustainability research must better consider the dynamics of farming systems and the agency of farmers in on-farm biogas development.\u003c/p\u003e","manuscriptTitle":"Accounting for systemic effects of anaerobic digestion development on farmers’ practices: implications for environmental assessment","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-03 13:27:14","doi":"10.21203/rs.3.rs-5219576/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-11-21T12:43:19+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-11-20T16:22:44+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Agronomy for Sustainable Development","date":"2024-10-17T09:31:26+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-08T12:08:55+00:00","index":"","fulltext":""},{"type":"submitted","content":"Agronomy for Sustainable Development","date":"2024-10-07T12:13:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"agronomy-for-sustainable-development","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ASDE","sideBox":"Learn more about [Agronomy for Sustainable Development](https://www.springer.com/journal/13593)","snPcode":"13593","submissionUrl":"https://www2.cloud.editorialmanager.com/asde/default2.aspx","title":"Agronomy for Sustainable Development","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"5fe3ada1-c895-4596-bd57-587c7ddf6238","owner":[],"postedDate":"December 3rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-12T09:58:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-03 13:27:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5219576","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5219576","identity":"rs-5219576","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}