Supercritical Water Gasification and Oxidation for Waste Treatment: A Systematic Review of Feedstocks, Catalysts, and Scale-Up Strategies

Supercritical Water Gasification and Oxidation for Waste Treatment: A Systematic Review of Feedstocks, Catalysts, and Scale-Up Strategies | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Systematic Review Supercritical Water Gasification and Oxidation for Waste Treatment: A Systematic Review of Feedstocks, Catalysts, and Scale-Up Strategies Alif Ali Jony, Md Ahmed Hussain, Nawrin Tamanna Rasha, Najmin Tamanna Bonna, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7988523/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In recent times, Supercritical Water Gasification (SCWG) and Supercritical Water Oxidation (SCWO) technologies are rapidly advancing as promising solutions for solid & liquid waste management. We conducted a systematic review on various feedstocks (sewage sludge, oily sludge, industrial waste, biomass, animal wastes, and pharmaceutical effluents), using multiple types of catalysts (alkaline, Ni-Mo, Ru-based & hybrid), and the scale-up challenges together. The methodology used in this review paper follows the PRISMA guidelines, including literature search, inclusion and exclusion criteria, and content analysis. The dataset for this systematic review paper solely selects journal articles on either SCWG or SCWO published between 2020 and 2025, resulting in 86 papers after screening and excluding irrelevant ones. The findings underscore the critical need for scalable, durable catalysts and reactor design that will address waste issues. This integration of SCWO and SCWG is highly feasible for destruction and energy recovery from waste. Partial advancements include modular heater design, ultrasonic descaling, autothermal operation using methane and ethanol co-fuel, and salt recovery modelling. It will be possible to take this technology to a sustainable and commercial level through low-cost and long-life catalysts, real-time salt control, and hybrid SCWG-SCWO coupling. Environmental Engineering Supercritical water gasification oxidation scale-up waste treatment Figures Figure 1 Figure 2 1. Introduction The waste generated from various feedstock makes up considerable amounts of solid and liquid waste generated in many countries, requiring rigorous solutions and approaches to deal with it. Research on sewage, industrial, biomass, and animal waste in catalysts development for SCWO and SCWG has emerged as a critical area of inquiry and development due to its potential for waste treatment. Traditional waste management techniques such as incineration, landfill, or biological treatment have often proven ineffective due to their low efficiency, secondary pollution, and inadequate energy recovery. The evolution of Supercritical water (SCW) based technologies, especially SCWG and SCWO have provided an opportunity for simultaneous waste disposal and resource valorization, H₂-rich syngas, N & P restoration [ 2 , 3 ]. Therefore, recent studies concentrated on converting waste into an energy source to find alternatives, where the most promising are Supercritical Water Gasification and Supercritical Water Oxidation. In SCW states, water remains T°C > 374°C, P > 22.1MPa, and combines to act as a solvent and reactant. At that state, the water dielectric state remains constant, and the ionic product changes rapidly; consequently, organic, gasification, and oxidation occur quickly. It creates an environment where organic waste can easily break down and turn into H 2 , CO 2 , and H 2 O, which helps regenerate energy with the destruction of waste. SCWG is a promising technology that enables gasification of wet biomass by utilizing the superior solvent properties of water at temperature and pressure above 374°C and 22.1 MPa, respectively and SCWO utilizes the unique properties of supercritical water; beyond its critical point (T > 374 ◦C, P > 22.1 MPa), the supercritical water medium rapidly dissolves the organic molecules and oxidants, reducing mass transfer limitations and providing high concentrations of free radicals [ 4 ]. It creates an environment where organic waste can easily break down and turn into H2, CO2, and H2O, which helps regenerate energy with the destruction of waste. In recent studies [ 5 ], work on pharmaceutical waste by applying SCWO showed that, without catalysts, the feasibility of 99.5% TOC removal can be achieved, and with catalysts, 99.9% Total Organic Carbon (TOC) removal can be achieved, which underscores the radical pathway that helps to oxidize. Recent research has shown that the SCWO process can degrade approximately > 99.9% of per and polyfluoroalkyl substances (PFAS), can remove 94 to 99.7% in continuous SCWO, and pharmaceuticals like refractory pollutants and concentrate the feedstock can also reduce the heating load [ 6 , 7 ]. On the other hand, SCWG provides high Hydrogen yield (~ 18–19 mol/kg) and Carbon efficiency (CE > 90%) from sludge, oily sludge, and manure [ 8 , 9 ]. With catalysts, syngas can be up to 9.1 to 14.2 mol/kg when adding catalysts K2CO3 [ 10 ]. It has enhanced the efficiency of process intensification strategies like thermal-alkaline pretreatment [ 8 ]. Alkali catalysis and nutrient recovery and struvite crystallization [ 11 – 13 ]. Hybrid approaches, such as methane-assisted SCWO and CO₂-assisted SCWG, have ensured energy savings and utilization of greenhouse gases [ 14 , 15 ]. Alongside, the discovery of the salt deposition mechanism of black liquor SCWG and continuous gasification performance analysis of grease trap sludge has advanced the research towards practical implementation [ 16 , 17 ]. Another study showed that combining SCWO with ultrasonics can remove the chromium from the solid wholly and 99%, and the TOC removal efficiency is more than > 99.9% [ 18 ]. Another paper adds methane with SCWO, showing that it helps to minimize energy demand, 1.3 to 1.5 times energy consumption from an external source, though salt management and corrosion still [ 19 ]. Despite progress, significant challenges remain unresolved despite these developments, high energy requirements- maintaining the system of ≥ 500–750°C & ≥22 MPa is costly [ 20 – 22 ]. Additionally, the complexity of feedstocks such as sewage sludge, oily sludge, biomass, animal and pharmaceutical effluent catalytic and scalability remain a challenge [ 23 – 24 ]. Moreover, Salt precipitation, scaling & corrosion are significant obstacles to reactor stability [ 17 , 25 ]. Catalyst-related issues such as Ni deactivation, high value of Ru, alkali leaching, and corrosivity of AlCl₃ [ 26 – 29 ]. Incomplete mineralization- consequently, phenols, PAHs, nitrogenous aromatics, and lignin/lipids like residues persist [ 1 , 30 – 31 ]. In scale-up limitations, most of the work is limited to laboratories or batch-scale reactors. In very few cases, it has been field-tested or continuously tasted [ 32 – 33 ]. Sustainability gap- LCA, techno-economic assessment, and long-term environmental impact analysis are very limited [ 12 , 34 ]. This review adopts the PRISMA guidelines as its methodological sections, showing screening, retrieval, and searching and exclusion criteria of the research and bibliometric and content analysis, and showing the current research, gap, and the recommendations for future researchers, all the papers mostly connected to SCWG or SCWO in waste treatment. The following section of this paper exhibits the methodological sections, examining the current research interest in SCWG and SCWO, or the achievements acquired currently. Additionally, synthesize all the information into a single frame for better comprehension of current research and future recommendations for the researchers. Finally, the review conducts research findings and suggests research directions on the identified gaps in waste treatment by SCW technologies. The novelty of this study is to critically analyze and synthesize the current work on SCW technologies in waste treatment, identifying prevailing research gaps and feasible recommendations for future researchers, while previous research particularly focused on specific feedstocks. Consequently, this study aims to combine all the data and current work on SCWG/SCWO in waste treatment and explore the scale-up challenges and threats it poses and showing the hybrid process of SCWG and SCWO. This approach provides a comprehensive understanding of the current scenario in the field of waste treatment, delineating possible solutions and innovative insights with various types of feedstocks, including sewage, industrial, biomass, pharmaceutical, and animal wastes. By extracting and analyzing key findings, researchers, stakeholders, and policymakers can generate a comprehensive understanding of the current state of research. 2. Methods This study was conducted using the Systematic Literature Review (SLR) methodology to screen the articles. The first step to the SLR methodology is to plan to search for relevant articles [ 35 ]. After the panel members select the particular journal set, they include and exclude criteria and review the selected publications. The present SLR was conducted in five stages. The first stage involved setting search keywords and inclusion and exclusion criteria. Next the author searched the database to extract relevant articles for this systematic review. After ending with these steps, implementing the requirements already provided, they are documented the result of the SLR . 2.1. Planning the review The SLR main objective is to analyze and understand the existing scholarly work in the waste treatment in SCWG and Oxidation, particularly in feedstock type, catalyst, and scale-up challenges. The author mainly chose two databases, Web of Science and Scopus. Primarily select keywords for search, with a focus on Supercritical water, gasification, and oxidation in waste treatment, excluding subcritical water focus and other topics. The author searched with the keywords on WoS and, without a filter, found around 2463 articles, while after the filter, it turned out to be 420 articles. The author also searched without a filter and saw 2442, and after the filter, it was 511 articles. To ensure the accountability of the SLR process and eliminate biases in the review processes, the author consulted with the panel members to reach a final keywords list. The study involves establishing inclusion and exclusion criteria presented in Table 2 . These criteria helped to refine the list of studies obtained in the keyword search. There were numerous articles published in WoS, so we chose only journal articles over others, such as book chapters, conference articles, and others. To limit the number of publications, we concentrated on those where either SCWG or SCWO are present in waste treatment, with a focus on waste type, scale, and the reactor use, including the article. Table 1 Search strings Note: Boolean operators are capitalized; use straight quotes in databases that require them. Supercritical Water Waste Treatment Search String ("supercritical water" OR SCW OR "supercritical Gasification" OR "supercritical water oxidation" OR SCWO OR "supercritical water gasification" OR SCWG OR " oxidation" OR "gasification" ) ("wastewater" OR "municipal wastewater" OR "industrial wastewater" OR "pharmaceutical wastewater" OR sludge OR "sewage sludge" OR sewage OR biosolids OR effluents OR "wastewater treatment") (("supercritical water" OR SCW OR "supercritical Oxidation" OR "supercritical water oxidation" OR SCWO OR "supercritical water gasification" OR SCWG OR " oxidation" OR " gasification" OR "liquefaction") AND ("wastewater" OR "municipal wastewater" OR "industrial wastewater" OR "pharmaceutical wastewater" OR sludge OR "sewage sludge" OR sewage OR biosolids OR effluents OR "wastewater treatment")) Table 2 Inclusion and Exclusion SL NO Inclusion Criteria Exclusion Criteria 1 Publication Year: Between 2020 and 2025 Publication Stage: Preprint, abstract, book chapter, non-peer-reviewed reports. 2 Language: Only published in English Language: Non-English Publications. 3 Type of publication: Journal article Irrelevant Technology: Focus only on pyrolysis, subcritical water, incineration, and anaerobic digestion. 4 Subject Area: Environmental Science and Engineering Irrelevant Subject Area: Papers on water, incineration, and Supercritical CO2, subcritical methanol, or other fluid (not water) 5 Technology focus: Supercritical Gasification (SCWG) and Supercritical Water Oxidation (SCWO) Related to waste treatment, Duplicate: Same data in multiple formats (keep only the most comprehensive) 6 Research Scope: Feedstock types Catalysts Scale up Reactor type Publication Year: Before 2020 not included in systematic analysis. 2.3. Data Extraction The final selected keywords were searched in the WoS and Scopus with the help of a Boolean Logic search string, such as the application of “AND” and “OR” connectors. The author then searched in titles, abstracts, and keywords in the Scopus and WoS databases. The date of the search was September 2, 2025. By initially searching with search keywords, an article was found 2442 after setting the filter 511 obtained from the Scopus database, while 2439 data were found in the WoS after setting the filter 420. Then the duplicate value from these two datasets was found to be 561, and finally, the article was 370. The authors then invited the review panels to further filter the remaining articles. The elimination process involved reading the title and abstract. Two steps were taken twice to ensure the paper's accountability, and a total of 222 articles were identified. In the next stage, the panel member shared the short-listed articles. After that, the panel member was eliminated because it focused only on the SCW mechanism behavior, non-waste application, or failure to find key elements; then the article came to 140. After that, panel members started to fully text analyze and eliminate articles that are not explicitly focused on supercritical water gasification or oxidation (SCWG/SCWO), instead focusing on the behavior or mechanism of SCW, and finally 120 articles were selected for the systematic review, which primarily focus on SCWO and SCWG with the major core aspects, final number of articles selected was 86 in this review. In the final Stages, the panel recommends studying 86 papers, and the author then developed the research profile for the selected studies. Figure 1 depicts the SLR process in a PRISMA diagram. 2.4. Data Execution & Research Profiling This section mainly describes the research profile of the pool of studies in the sample. The results presented in this section assess the current research based on the last six years, 2020–2025. Organizing and summarizing the research profile in a particular domain of knowledge delineates the direction and momentum of the research field. Fig., which presents the time-wise proliferation of research on the interaction of the SCW in waste treatment, the challenges, and the experimental area. Records were identified from Web of Science and Scopus without filtering, just giving the title we found from WoS, n = 2463, and from Scopus, n = 2442. After setting our inclusion and exclusion criteria from WoS, it comes to 420, and from Scopus, it's 561. The sum of the after filter is 981. Then we checked the duplicated value, we found n = 572 duplicates after removing them, and the count comes to 409. Then we started to read the title and abstract to form another n = 177 excluded, which mainly excluded because not core related to waste treatment or SCWG /SCWO, not the central core part. Some are mechanical focus; some are not waste-related. Then we have 232 papers. Then we divided with our panel members, five for complete text analysis; they all excluded in total n = 115, the main reason was the HTL (Hydrothermal Liquefaction) pathway, not SCWG/SCWO. Then we rechecked and tried to download all the PDFs we could not retrieve — 16 PDFs — and excluded 15 more. And finally, in our systematic review, we selected 86 studies. Figure 2 shows the distribution of publications over six years, clearly showing an emerging topic in the modern world. From 2020 to 2025, it showed some variability, while from 2023 to 2025, it showed the highest number of publications, which indicates the current emerging solution and work in SCWG and SCWO. These trends suggest that this topic has gained attention from the scientific community. Table 3 Number of included articles by journal (n = 86) Rank Journal n 1 Chemical Engineering Journal 9 Journal of Water Process Engineering 9 2 Energy 7 3 Journal of Environmental Chemical Engineering 6 4 Journal of Cleaner Production 5 Water Research 5 Journal of Hazardous Materials 5 Chemosphere 5 5 Biomass and Bioenergy 4 Process Safety and Environmental Protection 4 6 Journal of Environmental Management 3 7 International Journal of Environmental Science and Technology 2 Application of Supercritical Water Oxidation to Effectively Destroy Per- and Polyfluoroalkyl Substances in Aqueous Matrices 2 Water 2 Journal of Chemical Technology & Biotechnology 2 Others with one article 16 It is evident in Table 3 that a few journals that are highly concentrated on SCWO and SCWG in waste treatment, such as J Water Process, Chem Eng J, and Energy, dominate the field. At the same time, many others have only one or two publications, which indicate limited research diversity and highlight the scope of the work. 3. Results and Discussion Integration of Supercritical Water Gasification (SCWG) and Supercritical Water Oxidation (SCWO) for Sustainable Wastewater Treatment and Energy Recovery: SCWO and SCWG achieved destruction of hazardous waste but also for energy recovery though energy demand to running operation and clogging remain unsolved. 3.1. Core concept In the current industrialized society, waste is not just a source of pollution but a source of energy. Supercritical Water Oxidation and Supercritical Water Gasification are two SCW technologies based on the principle of physics, which occur when water exceeds its critical point (374 ° C, 22.1 MPa). It has the characteristics of liquid and gas. In this situation, organic waste and contaminants are quickly broken down, resulting in the complete oxidation of the SCWO and partial gases in SCWG. Therefore, these two processes can be seen together as a circular waste-to-energy technology where it is possible to refine water, reduce contamination, and restore energy from waste. 3.2. Technological Progress According to Ma et al. [ 37 ] it is possible to remove 99% Cr (Chromium) and > 99.9% TOC by a combination of SCWO and ultrasonic, which is an important achievement in solid waste reproduction. As illustrated through simulation, auto thermal operation and 78.95% energy recovery efficiency can be achieved; SCWO can be an energy-positive wastewater [ 38 , 39 ]. Another significant achievement showed by Chen et al. [ 40 ] is that mixed plastic SCWG achieved 106.8% GE and H₂ yield 15.1 mol/kg H 2 yield, which is higher than single plastic due to synergistic effects [ 41 ], using K₂CO₃/H₂O₂ catalyst, have achieved 15.5 mol/kg H₂ yield using catalysts and have proven that catalysts accelerate WGSR (Water-Gas-Shift-Reaction). Fedyaeva et al. [ 19 ] highlighted that energy consumption has reduced by 1.3–1.5 times through the addition of methane, although salt precipitation and corrosion remain unsolved. Mourão et al. [ 42 ] showed that 74.74–98.8% carbon conversion and H 2 yield of 2.18 mol/Mol C are available by SCWG in the biodiesel industry [ 43 ] and achieved an H₂ 72.4% from textile waste and a gasification efficiency of 72.4%. 3.3. Environmental & Energy Relevance It provides a combined analysis of these studies that SCWO waste almost entirely eliminates organic and heavy metal contamination (TOC and COD removal > 99%). In the SCWG process, it is possible to convert the wastewater into an energy source, where H₂ yield is between 2.18–15.5 mol/kg.AI-Integrated Optimization. Ma et al. [ 44 ] Proven that a data-driven model can improve these processes. In real tests [ 39 ] a heat recovery efficiency ≈ 79% and 674.26 W thermal output were found in simulation, which gives direction of an energy-positive system. 3.4. Restrictions and Challenges There are some serious problems in reimplementing these technologies such as catalyst deactivation and fouling - carbon and salt deposits disable the catalyst [ 45 , 46 ]. Also, salt precipitation and reactor corrosion, metal damage, and clogging are major problems at high temperatures[ 28 ]. Feedstock diversity limitation - most research is limited to a single [ 47 , 48 ]. AI and simulation model limitation - yet single objective [ 49 ]. Industrial Scalability - Most studies are limited to the laboratory or Aspen Plus simulation level [ 38 , 39 ]. Life Cycle and Economic Analysis deficit - practical cost and environmental impact are not completely analyzed. 4. Future Research Directions Improving the life span of the catalyst and enhancing the regeneration process, as well as corrosion-resistant alloy and self-cleaning reactor design. However, hybrid process integration with SCWG and SCWO provides a new feasibility in waste treatment; the current focus should be on AI-based multi-objective optimization (H₂ yield, exergy, CO₂ minimization); Pilot-scale continuous reactor validation. Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA) should also be explored. SCWO and SCWG are two complementary processes of wastewater treatment. SCWO reduces environmental pollution, whereas SCWG produces energy from the process. Both combinedly produce a Zero Waste and Energy-Positive Circular Wastewater System, but for successful implementation in the industrial field, materials stability, salt control, and multi-optimization techniques’ reliability, and also more research is needed. A promising approach to sustainable wastewater treatment is the combination of SCWG and SCWO, which allows for both energy recovery and pollutant elimination at the same time. To attain a circular, energy-positive future, integrated process modeling, material innovation, and pilot-scale validation are necessary to overcome the remaining significant obstacles of catalyst deactivation, corrosion, and limited scalability. 5. Scale Up Challenges The systematic review of recent studies between 2020–2025 based on SCWG and SCWOIO is proof that large-scale studies have not been fully explored due to engineering and operational constraints. Fouling, catalyst positioning, and reduced lifetime innovation, such as ultrasonic descaling and modular heater design, are mostly caused by salt precipitation and corrosion [ 50 ]. Although due to salt recovery modeling by [ 51 ] and co-fuel assisted operation [ 32 ], their performance has been improved on a short-term basis, their long-term performance is still unproven. Economic viability is often limited due to energy demand and autothermal inefficiency. Current CFD modeling, hybrid reactor design, and energy interaction [ 52 ] optimization show a promising future, but they mostly remain theoretical. Therefore, the future work should still maintain its research focus on how to make the industrial-scale operation of SCWG and SCWO in waste treatment more sustainable. 5.1 Precipitation of salt and Plugging Salt precipitation is a basic limitation for continuous SCWG and SCWO operation. Recently, a salt nucleation model that achieved 69% Na/K carbonate recovery [ 51 ] and modular heater designs with ultrasonic descaling for salt formation reduction [ 53 ] were developed. But still, wall fouling and corrosion are persistent, and ultrasonic descaling is not industrially validated. To improve operational stability, Future research should focus more on pre-nucleation salt separation, salt-tolerant materials such as Inconel 740H and Hastelloy C-276, and self-cleaning continuous reactors. 5.2 Corrosion and Degradation of metal Longevity of reactor and its performance is significantly affected by corrosion. In hot zones, Na/K carbonate corrosion rates were three times higher [ 51 ], and Monel 400 ejectors with cooling sprays were used to reduce corrosion [ 50 ]. On the other hand, KOH additives delayed scaling but increased corrosion [ 54 ]. Nonetheless, no anti-corrosive coating has been validated that exceeds 1000 hours, and chloride oxygen synergistic corrosion remains unresolved. To minimize oxidation stress, future work should focus more on coated alloy liners, in reactor corrosion monitoring sensors, and optimized O 2 injections. 5.3 Reactor Design and Flow Management: For continuous operation, efficient reactor design is a must. CFD-thermodynamic modeling is used to identify hot-spot flow zones [ 51 ], and modular multi-point heaters reduce thermal stress [ 55 ]. To demonstrate operational stability, a 90-minute continuous run was performed; to run operational stability [ 1 ], however, continuous operation remains limited to ≤ 2 hours due to flow mal-distribution and incomplete oxidation. So future studies should apply multiphase CFD optimization, explore fluidized-bed salt-tolerant reactors, and scale up to 1000-hour pilot tests using real feed stocks. 5.4 Energy Demand and Autothermal Operation High energy demand is still a major limitation. Ethanol-assisted SCWO achieved near-autothermal performance [ 56 ], while methane co-fuel addition reduced heating load by 1.5 times [ 32 ]. While simulation modeling minimized requirements for utilities up to 60% [ 57 ], full auto thermal operation has not been achievable. Corrosion is often increased by co-fuel injections, and renewable energy integration remains limited. For efficiency improvement, future studies should focus more on development of co-fuel systems with waste heat recovery and exploration of hybrid SCWG-SCWO configurations. 5.5 Catalyst Deactivation and Stability Due to catalyst degradation, long-term operation is often hindered. Catalysts which are Ru-based show high performance but are costly [ 58 ], while Ni catalysts are prone to sulfur and chlorine poisoning [ 9 ]. Although KOH catalysts achieved 99% transformation, they suffered from leaching [ 8 ]. The short lifespan and the catalyst’s high cost remain an unresolved problem. So future works should focus on investigating Ni-Mo-Fe bimetallic catalysts, in-situ regeneration, and hybrid alkali-metal catalysts to enhance stability and reduce costs. 5.6 Effluent Quality and Toxic materials Although SCWG and SCWO can demonstrate high degradation efficiency, residual toxicity always remains an issue. [ 59 ] achieved 85% COD removal in his research, but pyridines and quinolines remained. Similarly, Peng et al. [ 60 ] discovered that PAHs contamination slowly occurs in the oily wastewater. Persistent PAHs, phenolics, and nitrogen compounds exhibit limited treatment, totality, and ecotoxicity testing. However, some serious problems can be witnessed at the time of reimplementing these technologies: Catalyst deactivation and fouling - carbon and salt deposits are used to disable the catalyst [ 32 , 61 ]. 6. Conclusion and Recommendations Waste generation from multiple feedstocks is omnipresent and has emerged as a global concern and crucial topic in energy recovery and waste destruction by SCW technologies. SCWO and SCWG methods have been effectively used for the treatment of various wastes such as sewage sludge, oily sludge, industrial waste, animal waste, biomass, and pharmaceutical residues with energy recovery. High levels of Carbon efficiency (90–99%) and pollutant removal efficiencies (99.9%) with energy recovery and production of Syngas have been found. The objective of this review was to highlight the current scenario of SCWG and SCWO in waste treatment. The findings of this paper suggest that SCWO and SCWG are more effective in waste treatment, such as 99.99% destruction of organic compounds and energy recovery. The paper also identified the central issue still unsolved and discussed the scale-up challenges in waste treatment, the operational cost, and the high energy demand to operate SCW technologies. The result of this study has significant implications, indicating that there is a high time to undertake necessary steps to integrate SCWG and SCWO in hazardous waste treatment as well as energy recovery with low cost and without catalysts. Future research should focus on developing low-cost and long-life Ni-Fe-Mo-based hybrid catalysts, real-time salt separation systems, and renewable auto-thermal reactor designs. Moreover, to evaluate environmental and economic feasibility, focus should be on comprehensive Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA), with coupling SCWG and SCWO in waste treatment to enhance waste treatment efficiency. SCW technology can perform better if the energy demand can be reduced. Declarations Ethical approval All authors have read, understood, and have complied as applicable with the statement on “Ethical responsibilities of Authors” as found in the Instructions for Authors. This is to certify that this paper is an original academic work. The authors declare that all the ethical standards applicable to “Waste and Biomass Valorization” have been complied with. Acknowledgment: We want to thank our committed team members for their invaluable support during this project. We also extend heartfelt thanks to Mayesha Farzana Mumu, studying MBBS in Sylhet Women’s Medical College, for her constant support and encouragement throughout this research journey. Competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Data availability: No data was used for the research described in the article. Funding: This review was carried out independently and did not receive any financial aid. References Wang L et al (Mar. 2025) Experimental study on supercritical water gasification of grease trap sludge in a continuous reactor. Biomass Bioenergy 194:107636. 10.1016/j.biombioe.2025.107636 Chen Y, He Y, Jin H, Guo L (Apr. 2020) Resource utilization of landfill leachate gasification in supercritical water. Chem Eng J 386:124017. 10.1016/j.cej.2020.124017 Du M, Liu S, Sun J, Jin H, Chen Y, Guo L (2023) ‘Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts’, J. Clean. Prod. , vol. 420, p. 138455, Sep. 10.1016/j.jclepro.2023.138455 Adar E, Ince M, Bilgili MS (2020) ‘Characteristics of Liquid Products in Supercritical Water Gasification of Municipal Sewage Sludge by Continuous Flow Tubular Reactor’, Waste Biomass Valorization , vol. 11, no. 11, pp. 6321–6335, Nov. 10.1007/s12649-019-00858-9 Mylapilli SVP, Reddy SN (May 2022) Catalytic and non-catalytic degradation of acetaminophen in supercritical water. Environ Res 207:112191. 10.1016/j.envres.2021.112191 Rosansky S et al (2024) ‘Field Demonstration of PFAS Destruction in Various Alcohol-Resistant AFFFs Using Supercritical Water Oxidation (SCWO)’, ACS EST Water , vol. 4, no. 10, pp. 4486–4496, Oct. 10.1021/acsestwater.4c00499 Webb H et al (Nov. 2025) PFAS destruction using supercritical water oxidation (SCWO) at Peterson Space Force Base. J Hazard Mater Lett 6:100156. 10.1016/j.hazl.2025.100156 Chen Y, Yi L, Li S, Yin J, Jin H (May 2020) Catalytic gasification of sewage sludge in near and supercritical water with different catalysts. Chem Eng J 388:124292. 10.1016/j.cej.2020.124292 Du M, Liu S, Sun J, Jin H, Chen Y, Guo L (2023) ‘Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts’, J. Clean. Prod. , vol. 420, p. 138455, Sep. 10.1016/j.jclepro.2023.138455 Cui J, Wang H, Hantoko D, Wen X, Kanchanatip E, Yan M (Oct. 2023) Nitrogen and phosphorus recovery from sludge treatment by supercritical water gasification coupled with struvite crystallization. J Water Process Eng 55:104070. 10.1016/j.jwpe.2023.104070 Cheng J, Nouri Gehraz SA, Khodamoradi S, Jani Qali D, Jasim DJ (Nov. 2024) H2-rich gas production from gasification of oily sludge via supercritical water technology: Synergy effect of KOH, K2CO3, and reaction parameters. Chem Eng Process - Process Intensif 205:110008. 10.1016/j.cep.2024.110008 Cui J, Wang H, Hantoko D, Wen X, Kanchanatip E, Yan M (Oct. 2023) Nitrogen and phosphorus recovery from sludge treatment by supercritical water gasification coupled with struvite crystallization. J Water Process Eng 55:104070. 10.1016/j.jwpe.2023.104070 Zhang Y, Zhang S, Li H, Wang C, Jiang F, Lyu J (2020) ‘Treatment of municipal sludge by hydrothermal oxidation process with H2O2’, Chemosphere , vol. 257, p. 127140, Oct. 10.1016/j.chemosphere.2020.127140 Fedyaeva ON, Morozov SV, Vostrikov AA (2021) ‘Supercritical water oxidation of chlorinated waste from pulp and paper mill’, Chemosphere , vol. 283, p. 131239, Nov. 10.1016/j.chemosphere.2021.131239 Hu Y et al (2021) ‘CO2-assisted catalytic municipal sludge for carbonaceous biofuel via sub- and supercritical water gasification’, Energy , vol. 233, p. 121184, Oct. 10.1016/j.energy.2021.121184 Lu L et al (Jan. 2025) Mechanism of salt deposition, nucleation and separation in the supercritical water gasification of black liquor. Chem Eng J 506:159914. 10.1016/j.cej.2025.159914 Wang L et al (Mar. 2025) Experimental study on supercritical water gasification of grease trap sludge in a continuous reactor. Biomass Bioenergy 194:107636. 10.1016/j.biombioe.2025.107636 Ma M, Zhang S, Chen Y, Chen B, Guo L (Oct. 2024) Optimization of hydrogen-rich syngas from coal and sewage sludge co-gasification in supercritical water. Chem Eng J 497:154792. 10.1016/j.cej.2024.154792 Fedyaeva ON, Alekhin SA, Morozov SV, Vostrikov AA (2024) ‘Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode’, Biomass Bioenergy , vol. 188, p. 107324, Sep. 10.1016/j.biombioe.2024.107324 Li G, Niu M, Chen Y (Jan. 2025) Experimental and kinetic modeling study of oxidative degradation of benzene and phenol in supercritical water. J Environ Manage 373:123992. 10.1016/j.jenvman.2024.123992 Liu S, Ge Z, Du M, Guo L (Jan. 2023) Supercritical water partial oxidation of indole: Reaction variables, migration pathways, and nitrogen distribution. Chem Eng J 451:138638. 10.1016/j.cej.2022.138638 Peng Z et al (Jul. 2023) Clean treatment and resource utilization of oilfield wastewater using supercritical water gasification. J Clean Prod 411:137239. 10.1016/j.jclepro.2023.137239 Qiu Y, Liu Y, Zhang F, Rong W (2024) ‘Thermodynamic and exergy assessments of supercritical water gasification of oily sludge assisted by hydrothermal flame’, Energy , vol. 296, p. 131212, Jun. 10.1016/j.energy.2024.131212 Yan M, Hantoko D, Kanchanatip E, Zheng R, Zhong Y, Mubeen I (2020) ‘Valorization of sewage sludge through catalytic sub- and supercritical water gasification’, J. Energy Inst. , vol. 93, no. 4, pp. 1419–1427, Aug. 10.1016/j.joei.2020.01.004 Luo C, Fan X, Tang S, Xi H (Sep. 2025) Comparative study of alcohol co-oxidation for enhanced phenol degradation in wastewater under supercritical water oxidation (SCWO) conditions. J Water Process Eng 77:108477. 10.1016/j.jwpe.2025.108477 Chen Y, He Y, Jin H, Guo L (Apr. 2020) Resource utilization of landfill leachate gasification in supercritical water. Chem Eng J 386:124017. 10.1016/j.cej.2020.124017 Du M, Liu S, Sun J, Jin H, Chen Y, Guo L (2023) ‘Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts’, J. Clean. Prod. , vol. 420, p. 138455, Sep. 10.1016/j.jclepro.2023.138455 Li Y et al (Jun. 2024) Supercritical water oxidation for the treatment and utilization of organic wastes: Factor effects, reaction enhancement, and novel process. Environ Res 251:118571. 10.1016/j.envres.2024.118571 Zhang H et al (May 2020) Alkali-catalyzed supercritical water gasification of sewage sludge: effect of liquid residue reuse as homogenous catalyst. Int J Environ Sci Technol 17(5):2845–2852. 10.1007/s13762-020-02697-x Li L, Peng P, Wang G, Li X, Cao W, Gong Z (2025) ‘Study on the gasification mechanisms of key intermediates of oily sludge in supercritical water by ReaxFF-MD method’, Energy , vol. 330, p. 136907, Sep. 10.1016/j.energy.2025.136907 Peng Z et al (Jul. 2023) Clean treatment and resource utilization of oilfield wastewater using supercritical water gasification. J Clean Prod 411:137239. 10.1016/j.jclepro.2023.137239 Fedyaeva ON, Alekhin SA, Morozov SV, Vostrikov AA (2024) ‘Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode’, Biomass Bioenergy , vol. 188, p. 107324, Sep. 10.1016/j.biombioe.2024.107324 Rosansky S et al (2024) ‘Field Demonstration of PFAS Destruction in Various Alcohol-Resistant AFFFs Using Supercritical Water Oxidation (SCWO)’, ACS EST Water , vol. 4, no. 10, pp. 4486–4496, Oct. 10.1021/acsestwater.4c00499 Zhang H, Wang C, Zhang X, Zhang R, Ding L (2020) ‘Formation and inhibition of polycyclic aromatic hydrocarbons from the gasification of cyanobacterial biomass in supercritical water’, Chemosphere , vol. 253, p. 126777, Aug. 10.1016/j.chemosphere.2020.126777 Hina M, Chauhan C, Kaur P, Kraus S, Dhir A (Jan. 2022) Drivers and barriers of circular economy business models: Where we are now, and where we are heading. J Clean Prod 333:130049. 10.1016/j.jclepro.2021.130049 Kushwah S, Dhir A, Sagar M, Gupta B (2019) ‘Determinants of organic food consumption. A systematic literature review on motives and barriers’, Appetite , vol. 143, p. 104402, Dec. 10.1016/j.appet.2019.104402 Ma H, Li X, Zhu C, Chen F, Yang Y, Chen X (2020) ‘Liberation and recovery of Cr from real tannery sludge by ultrasound-assisted supercritical water oxidation treatment’, J. Clean. Prod. , vol. 267, p. 122064, Sep. 10.1016/j.jclepro.2020.122064 Ruya PM, Purwadi R, Lim SS (Feb. 2020) Supercritical water gasification of sewage sludge for power generation– thermodynamic study on auto-thermal operation using Aspen Plus. Energy Convers Manag 206:112458. 10.1016/j.enconman.2019.112458 Luo C, Teng S, Wang J, Xi H (Jan. 2024) Energy yield from wastewater by supercritical water oxidation process: Experimental validation and simulation from the viewpoint of energy system. Energy Convers Manag 299:117876. 10.1016/j.enconman.2023.117876 Chen Y, Yi L, Wei W, Jin H, Guo L (2022) ‘Hydrogen production by sewage sludge gasification in supercritical water with high heating rate batch reactor’, Energy , vol. 238, p. 121740, Jan. 10.1016/j.energy.2021.121740 Gong W et al (2023) Sep., ‘Catalytic gasification of textile wastewater treatment sludge for hydrogen production in supercritical water with K2CO3/H2O2: Reaction variables, mechanism and kinetics’, Int. J. Hydrog. Energy , vol. 48, no. 78, pp. 30310–30322. 10.1016/j.ijhydene.2023.04.160 Mourão LC et al (Apr. 2025) Continuous hydrogen production from biodiesel wastewater treatment via supercritical water gasification. Int J Hydrog Energy 116:486–496. 10.1016/j.ijhydene.2025.03.068 Thanikodi S, Sagade AA (2024) ‘Utilizing supercritical water gasification for hydrogen production combined with a waste heat recovery system for domestic households’, Results Eng. , vol. 24, p. 103432, Dec. 10.1016/j.rineng.2024.103432 Ma Z, Wang J, Feng Y, Wang R, Zhao Z, Chen H (2023) ‘Supercritical water gasification of organic solid waste: H2 yield and cold gas efficiency optimization considering modeling uncertainties’, Int. J. Hydrog. Energy , vol. 48, no. 79, pp. 30702–30717, Sep. 10.1016/j.ijhydene.2023.04.268 Fedyaeva ON, Alekhin SA, Morozov SV, Vostrikov AA (2024) ‘Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode’, Biomass Bioenergy , vol. 188, p. 107324, Sep. 10.1016/j.biombioe.2024.107324 Gong M, Chu H, Xu Q (Apr. 2024) Influences of reaction parameters and complexation pretreatments on the distribution of phosphorus during hydrothermal carbonization of dewatered sewage sludge. J Water Process Eng 60:105209. 10.1016/j.jwpe.2024.105209 Chen J, Fu L, Tian M, Kang S (2022) and J. E, ‘Comparison and synergistic effect analysis on supercritical water gasification of waste thermoplastic plastics based on orthogonal experiments’, Energy , vol. 261, p. 125104, Dec. 10.1016/j.energy.2022.125104 Mourão LC et al (Apr. 2025) Continuous hydrogen production from biodiesel wastewater treatment via supercritical water gasification. Int J Hydrog Energy 116:486–496. 10.1016/j.ijhydene.2025.03.068 Ma Z, Wang J, Feng Y, Wang R, Zhao Z, Chen H (2023) ‘Supercritical water gasification of organic solid waste: H2 yield and cold gas efficiency optimization considering modeling uncertainties’, Int. J. Hydrog. Energy , vol. 48, no. 79, pp. 30702–30717, Sep. 10.1016/j.ijhydene.2023.04.268 Yang J, Xie S, Wang S (Jun. 2024) Safety Management and Accident-Control Strategy for a Commercial-Scale Plant for Supercritical Water Oxidation of Sludge. Appl Sci 14(12):5101. 10.3390/app14125101 Lu L et al (Jan. 2025) Mechanism of salt deposition, nucleation and separation in the supercritical water gasification of black liquor. Chem Eng J 506:159914. 10.1016/j.cej.2025.159914 Pereira MB et al (2023) ‘Continuous Treatment of Refractory Wastewater from Research and Teaching Laboratories via Supercritical Water Oxidation–Experimental Results and Modeling’, Water , vol. 15, no. 22, p. 3926, Nov. 10.3390/w15223926 Yang C, Jiang Z, Wang S, Chen H, Zhang J, Li Y (Jan. 2025) Supercritical water oxidation of oily sludge: Operating parameters’ effects and reaction kinetics. J Water Process Eng 69:106871. 10.1016/j.jwpe.2024.106871 Chen Y, He Y, Jin H, Guo L (Apr. 2020) Resource utilization of landfill leachate gasification in supercritical water. Chem Eng J 386:124017. 10.1016/j.cej.2020.124017 Yang C, Jiang Z, Wang S, Chen H, Zhang J, Li Y (Jan. 2025) Supercritical water oxidation of oily sludge: Operating parameters’ effects and reaction kinetics. J Water Process Eng 69:106871. 10.1016/j.jwpe.2024.106871 Li G, Niu M, Chen Y (Jan. 2025) Experimental and kinetic modeling study of oxidative degradation of benzene and phenol in supercritical water. J Environ Manage 373:123992. 10.1016/j.jenvman.2024.123992 Pereira MB et al (Oct. 2023) Simultaneous recycling of waste solar panels and treatment of persistent organic compounds via supercritical water technology. Environ Pollut 335:122331. 10.1016/j.envpol.2023.122331 Galiwango E, Butler J, Lotfi S (2024) ‘A Review of Catalyst Integration in Hydrothermal Gasification’, Fuels , vol. 5, no. 3, pp. 375–393, Aug. 10.3390/fuels5030022 Montesantos N, Skjolding LM, Baun A, Muff J, Maschietti M (Feb. 2023) Reducing the environmental impact of offshore H2S scavenging wastewater via hydrothermal oxidation. Water Res 230:119507. 10.1016/j.watres.2022.119507 Peng P, Wang G, Li L, Ge H, Jin H, Guo L (2023) ‘Experimental investigation on the degradation of polymer-containing oily sludge in sub-/supercritical water’, Energy Sources Part Recovery Util. Environ. Eff. , vol. 45, no. 1, pp. 1983–1993, Apr. 10.1080/15567036.2023.2184001 Gong M, Chu H, Xu Q (Apr. 2024) Influences of reaction parameters and complexation pretreatments on the distribution of phosphorus during hydrothermal carbonization of dewatered sewage sludge. J Water Process Eng 60:105209. 10.1016/j.jwpe.2024.105209 Affolter J, Brunner T, Hagger N, Vogel F (Dec. 2022) A prototype system for the hydrothermal oxidation of feces. Water Res X 17:100160. 10.1016/j.wroa.2022.100160 Nunes LJR (2022) ‘Biomass gasification as an industrial process with effective proof-of-concept: A comprehensive review on technologies, processes and future developments’, Results Eng. , vol. 14, p. 100408, Jun. 10.1016/j.rineng.2022.100408 Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted 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-7988523","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Systematic Review","associatedPublications":[],"authors":[{"id":537439104,"identity":"eeb5d4fd-88c8-434f-a46b-85449e452691","order_by":0,"name":"Alif Ali Jony","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABBUlEQVRIie2RsUoDQRCGd1jBRrh2FsW8whwBCfgo9lYupDwhHiuB22btI0h8hdhcnbBwaQ6tg00ewCLlgQrOxcI0t6YU3K8Y9of5dmZZISKRPwiYtg4xEYdgCDMOUpo9FEJlJJjhoG4VCCvfkGBFiM118XNNJ9LeVdjQAJOxvJ2tpjcXiWWlycruxdzzpXKEiB7G6X251BMPBlz92q1Mrs7wiDAXHoq+KittWJFQhBX1wVN6Huz750OlH/dRjnkKEneSMiM9+1Vxdf/8hJW0VbCa6yc+LEJvSa1LV29ZjqdLuyYc5Xr64hfrJgsoRhzgTvbbOu/sZ3r8NZudnIeaI5FI5J/yBa0mWPtZ8J2LAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0009-0000-7315-6151","institution":"Sylhet Agricultural University, Sylhet, Bangladesh.","correspondingAuthor":true,"prefix":"","firstName":"Alif","middleName":"Ali","lastName":"Jony","suffix":""},{"id":537444643,"identity":"b26759be-9613-4d42-b5ca-fc98a0add61a","order_by":1,"name":"Md Ahmed Hussain","email":"","orcid":"","institution":"Sylhet Agricultural University, Sylhet, Bangladesh.","correspondingAuthor":false,"prefix":"","firstName":"Md","middleName":"Ahmed","lastName":"Hussain","suffix":""},{"id":537444644,"identity":"56fc90e2-5a75-4d8a-bd6c-f29530d5fd86","order_by":2,"name":"Nawrin Tamanna Rasha","email":"","orcid":"","institution":"Sylhet Agricultural University, Sylhet, Bangladesh.","correspondingAuthor":false,"prefix":"","firstName":"Nawrin","middleName":"Tamanna","lastName":"Rasha","suffix":""},{"id":537444645,"identity":"66e71c07-2ad1-475a-9469-6939a05ab4aa","order_by":3,"name":"Najmin Tamanna Bonna","email":"","orcid":"","institution":"Sylhet Engineering College. Sylhet, Bangladesh","correspondingAuthor":false,"prefix":"","firstName":"Najmin","middleName":"Tamanna","lastName":"Bonna","suffix":""},{"id":537444646,"identity":"0df55062-0251-4bb4-929d-31eb5bca9e95","order_by":4,"name":"Ahsan Habib","email":"","orcid":"","institution":"University of Chittagong, Chittagong, Bangladesh","correspondingAuthor":false,"prefix":"","firstName":"Ahsan","middleName":"","lastName":"Habib","suffix":""}],"badges":[],"createdAt":"2025-10-30 10:57:28","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7988523/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7988523/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":94826394,"identity":"c82ad78b-a456-48e0-88ab-aabdc7eeb7a8","added_by":"auto","created_at":"2025-10-31 06:51:33","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":103601,"visible":true,"origin":"","legend":"","description":"","filename":"WasteandBiomass.docx","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/ce6b86160e09461d66795471.docx"},{"id":94818439,"identity":"4cfc4f59-1929-4ab0-af6f-3e272482f138","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"json","order_by":1,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":342,"visible":true,"origin":"","legend":"","description":"","filename":"rs7988523.json","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/2e245bbd7f844dce131cd134.json"},{"id":94818438,"identity":"6685b460-76cd-4928-81df-8287d8da3cc4","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"xml","order_by":2,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":131589,"visible":true,"origin":"","legend":"","description":"","filename":"rs79885230enriched.xml","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/62bb918ebaa7257c6c4628c1.xml"},{"id":94818440,"identity":"cb8472bd-973d-442f-a26c-7b67aaca0cec","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"png","order_by":5,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":51710,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/771e421cc1133d4e3d6b5173.png"},{"id":94818437,"identity":"bf6ed5c2-827c-44e8-8902-eb56e6810245","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"png","order_by":6,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":13012,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/938c0306ee309f1bd423f44d.png"},{"id":94818441,"identity":"15d2b813-daf3-44e0-ad50-d18f1ca3d253","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"xml","order_by":7,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":130477,"visible":true,"origin":"","legend":"","description":"","filename":"rs79885230structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/ff97b2de7b68ddd5330c9a33.xml"},{"id":94818442,"identity":"17ce61e7-7ecc-410e-ac07-8cc0342358a3","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"html","order_by":8,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":140741,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/2d5cfca750b857a243b567c0.html"},{"id":94818434,"identity":"3e63fb75-3134-4a11-a1d5-4734ba0ba839","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":343807,"visible":true,"origin":"","legend":"\u003cp\u003eA PRISMA diagram illustrating the selection process for publications in this review.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/59a7d991c12faafe751899d7.jpeg"},{"id":94818436,"identity":"36df8e31-0788-45b6-a564-b26fbc3c0b7b","added_by":"auto","created_at":"2025-10-31 05:24:32","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":13883,"visible":true,"origin":"","legend":"\u003cp\u003eNumber of publications during 2020 and 2025\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/2ea01ad6745001089f9c2760.png"},{"id":94827386,"identity":"8ffb5317-f089-48fd-a2f6-b86bd1ec88cb","added_by":"auto","created_at":"2025-10-31 06:58:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1146212,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7988523/v1/ba5fde4e-a675-49c2-9cb1-4d9e7e718335.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eSupercritical Water Gasification and Oxidation for Waste Treatment: A Systematic Review of Feedstocks, Catalysts, and Scale-Up Strategies\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe waste generated from various feedstock makes up considerable amounts of solid and liquid waste generated in many countries, requiring rigorous solutions and approaches to deal with it. Research on sewage, industrial, biomass, and animal waste in catalysts development for SCWO and SCWG has emerged as a critical area of inquiry and development due to its potential for waste treatment. Traditional waste management techniques such as incineration, landfill, or biological treatment have often proven ineffective due to their low efficiency, secondary pollution, and inadequate energy recovery.\u003c/p\u003e\u003cp\u003eThe evolution of Supercritical water (SCW) based technologies, especially SCWG and SCWO have provided an opportunity for simultaneous waste disposal and resource valorization, H₂-rich syngas, N \u0026amp; P restoration [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Therefore, recent studies concentrated on converting waste into an energy source to find alternatives, where the most promising are Supercritical Water Gasification and Supercritical Water Oxidation. In SCW states, water remains T\u0026deg;C\u0026thinsp;\u0026gt;\u0026thinsp;374\u0026deg;C, P\u0026thinsp;\u0026gt;\u0026thinsp;22.1MPa, and combines to act as a solvent and reactant. At that state, the water dielectric state remains constant, and the ionic product changes rapidly; consequently, organic, gasification, and oxidation occur quickly. It creates an environment where organic waste can easily break down and turn into H\u003csub\u003e2\u003c/sub\u003e, CO\u003csub\u003e2\u003c/sub\u003e, and H\u003csub\u003e2\u003c/sub\u003eO, which helps regenerate energy with the destruction of waste.\u003c/p\u003e\u003cp\u003eSCWG is a promising technology that enables gasification of wet biomass by utilizing the superior solvent properties of water at temperature and pressure above 374\u0026deg;C and 22.1 MPa, respectively and SCWO utilizes the unique properties of supercritical water; beyond its critical point (T\u0026thinsp;\u0026gt;\u0026thinsp;374 ◦C, P\u0026thinsp;\u0026gt;\u0026thinsp;22.1 MPa), the supercritical water medium rapidly dissolves the organic molecules and oxidants, reducing mass transfer limitations and providing high concentrations of free radicals [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. It creates an environment where organic waste can easily break down and turn into H2, CO2, and H2O, which helps regenerate energy with the destruction of waste. In recent studies [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], work on pharmaceutical waste by applying SCWO showed that, without catalysts, the feasibility of 99.5% TOC removal can be achieved, and with catalysts, 99.9% Total Organic Carbon (TOC) removal can be achieved, which underscores the radical pathway that helps to oxidize.\u003c/p\u003e\u003cp\u003eRecent research has shown that the SCWO process can degrade approximately\u0026thinsp;\u0026gt;\u0026thinsp;99.9% of per and polyfluoroalkyl substances (PFAS), can remove 94 to 99.7% in continuous SCWO, and pharmaceuticals like refractory pollutants and concentrate the feedstock can also reduce the heating load [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. On the other hand, SCWG provides high Hydrogen yield (~\u0026thinsp;18\u0026ndash;19 mol/kg) and Carbon efficiency (CE\u0026thinsp;\u0026gt;\u0026thinsp;90%) from sludge, oily sludge, and manure [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. With catalysts, syngas can be up to 9.1 to 14.2 mol/kg when adding catalysts K2CO3 [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. It has enhanced the efficiency of process intensification strategies like thermal-alkaline pretreatment [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Alkali catalysis and nutrient recovery and struvite crystallization [\u003cspan additionalcitationids=\"CR12\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Hybrid approaches, such as methane-assisted SCWO and CO₂-assisted SCWG, have ensured energy savings and utilization of greenhouse gases [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Alongside, the discovery of the salt deposition mechanism of black liquor SCWG and continuous gasification performance analysis of grease trap sludge has advanced the research towards practical implementation [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Another study showed that combining SCWO with ultrasonics can remove the chromium from the solid wholly and 99%, and the TOC removal efficiency is more than \u0026gt;\u0026thinsp;99.9% [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Another paper adds methane with SCWO, showing that it helps to minimize energy demand, 1.3 to 1.5 times energy consumption from an external source, though salt management and corrosion still [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eDespite progress, significant challenges remain unresolved despite these developments, high energy requirements- maintaining the system of \u0026ge;\u0026thinsp;500\u0026ndash;750\u0026deg;C \u0026amp; \u0026ge;22 MPa is costly [\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Additionally, the complexity of feedstocks such as sewage sludge, oily sludge, biomass, animal and pharmaceutical effluent catalytic and scalability remain a challenge [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Moreover, Salt precipitation, scaling \u0026amp; corrosion are significant obstacles to reactor stability [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Catalyst-related issues such as Ni deactivation, high value of Ru, alkali leaching, and corrosivity of AlCl₃ [\u003cspan additionalcitationids=\"CR27 CR28\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Incomplete mineralization- consequently, phenols, PAHs, nitrogenous aromatics, and lignin/lipids like residues persist [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn scale-up limitations, most of the work is limited to laboratories or batch-scale reactors. In very few cases, it has been field-tested or continuously tasted [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Sustainability gap- LCA, techno-economic assessment, and long-term environmental impact analysis are very limited [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis review adopts the PRISMA guidelines as its methodological sections, showing screening, retrieval, and searching and exclusion criteria of the research and bibliometric and content analysis, and showing the current research, gap, and the recommendations for future researchers, all the papers mostly connected to SCWG or SCWO in waste treatment. The following section of this paper exhibits the methodological sections, examining the current research interest in SCWG and SCWO, or the achievements acquired currently. Additionally, synthesize all the information into a single frame for better comprehension of current research and future recommendations for the researchers. Finally, the review conducts research findings and suggests research directions on the identified gaps in waste treatment by SCW technologies.\u003c/p\u003e\u003cp\u003eThe novelty of this study is to critically analyze and synthesize the current work on SCW technologies in waste treatment, identifying prevailing research gaps and feasible recommendations for future researchers, while previous research particularly focused on specific feedstocks. Consequently, this study aims to combine all the data and current work on SCWG/SCWO in waste treatment and explore the scale-up challenges and threats it poses and showing the hybrid process of SCWG and SCWO. This approach provides a comprehensive understanding of the current scenario in the field of waste treatment, delineating possible solutions and innovative insights with various types of feedstocks, including sewage, industrial, biomass, pharmaceutical, and animal wastes. By extracting and analyzing key findings, researchers, stakeholders, and policymakers can generate a comprehensive understanding of the current state of research.\u003c/p\u003e"},{"header":"2. Methods","content":"\u003cp\u003eThis study was conducted using the Systematic Literature Review (SLR) methodology to screen the articles. The first step to the SLR methodology is to plan to search for relevant articles [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. After the panel members select the particular journal set, they include and exclude criteria and review the selected publications. The present SLR was conducted in five stages. The first stage involved setting search keywords and inclusion and exclusion criteria. Next the author searched the database to extract relevant articles for this systematic review. After ending with these steps, implementing the requirements already provided, they are documented the result of the SLR .\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Planning the review\u003c/h2\u003e\u003cp\u003eThe SLR main objective is to analyze and understand the existing scholarly work in the waste treatment in SCWG and Oxidation, particularly in feedstock type, catalyst, and scale-up challenges. The author mainly chose two databases, Web of Science and Scopus. Primarily select keywords for search, with a focus on Supercritical water, gasification, and oxidation in waste treatment, excluding subcritical water focus and other topics. The author searched with the keywords on WoS and, without a filter, found around 2463 articles, while after the filter, it turned out to be 420 articles. The author also searched without a filter and saw 2442, and after the filter, it was 511 articles. To ensure the accountability of the SLR process and eliminate biases in the review processes, the author consulted with the panel members to reach a final keywords list.\u003c/p\u003e\u003cp\u003eThe study involves establishing inclusion and exclusion criteria presented in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. These criteria helped to refine the list of studies obtained in the keyword search. There were numerous articles published in WoS, so we chose only journal articles over others, such as book chapters, conference articles, and others. To limit the number of publications, we concentrated on those where either SCWG or SCWO are present in waste treatment, with a focus on waste type, scale, and the reactor use, including the article.\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\u003cb\u003eSearch strings\u003c/b\u003e Note: Boolean operators are capitalized; use straight quotes in databases that require them.\u003c/p\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\u003eSupercritical Water\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWaste Treatment\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSearch String\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e(\"supercritical water\" OR SCW OR \"supercritical Gasification\" OR \"supercritical water oxidation\" OR SCWO OR \"supercritical water gasification\" OR SCWG OR \" oxidation\" OR \"gasification\" )\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(\"wastewater\" OR \"municipal wastewater\" OR \"industrial wastewater\" OR \"pharmaceutical wastewater\" OR sludge OR \"sewage sludge\" OR sewage OR biosolids OR effluents OR \"wastewater treatment\")\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e((\"supercritical water\" OR SCW OR \"supercritical Oxidation\" OR \"supercritical water oxidation\" OR SCWO OR \"supercritical water gasification\" OR SCWG OR \" oxidation\" OR \" gasification\" OR \"liquefaction\") AND (\"wastewater\" OR \"municipal wastewater\" OR \"industrial wastewater\" OR \"pharmaceutical wastewater\" OR sludge OR \"sewage sludge\" OR sewage OR biosolids OR effluents OR \"wastewater treatment\"))\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\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\u003eInclusion and Exclusion\u003c/p\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\u003eSL NO\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInclusion Criteria\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eExclusion Criteria\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePublication Year: Between 2020 and 2025\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePublication Stage: Preprint, abstract, book chapter, non-peer-reviewed reports.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eLanguage: Only published in English\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eLanguage: Non-English Publications.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eType of publication: Journal article\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eIrrelevant Technology:\u003c/p\u003e\u003cp\u003eFocus only on pyrolysis, subcritical water, incineration, and anaerobic digestion.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSubject Area:\u003c/p\u003e\u003cp\u003eEnvironmental Science and Engineering\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eIrrelevant Subject Area: Papers on water, incineration, and Supercritical CO2, subcritical methanol, or other fluid (not water)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTechnology focus:\u003c/p\u003e\u003cp\u003eSupercritical Gasification (SCWG) and\u003c/p\u003e\u003cp\u003eSupercritical Water Oxidation (SCWO)\u003c/p\u003e\u003cp\u003eRelated to waste treatment,\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDuplicate:\u003c/p\u003e\u003cp\u003eSame data in multiple formats (keep\u003c/p\u003e\u003cp\u003eonly the most comprehensive)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eResearch Scope:\u003c/p\u003e\u003cp\u003eFeedstock types\u003c/p\u003e\u003cp\u003eCatalysts\u003c/p\u003e\u003cp\u003eScale up\u003c/p\u003e\u003cp\u003eReactor type\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePublication Year:\u003c/p\u003e\u003cp\u003eBefore 2020 not included in\u003c/p\u003e\u003cp\u003esystematic analysis.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Data Extraction\u003c/h2\u003e\u003cp\u003eThe final selected keywords were searched in the WoS and Scopus with the help of a Boolean Logic search string, such as the application of \u0026ldquo;AND\u0026rdquo; and \u0026ldquo;OR\u0026rdquo; connectors. The author then searched in titles, abstracts, and keywords in the Scopus and WoS databases. The date of the search was September 2, 2025. By initially searching with search keywords, an article was found 2442 after setting the filter 511 obtained from the Scopus database, while 2439 data were found in the WoS after setting the filter 420. Then the duplicate value from these two datasets was found to be 561, and finally, the article was 370.\u003c/p\u003e\u003cp\u003eThe authors then invited the review panels to further filter the remaining articles. The elimination process involved reading the title and abstract. Two steps were taken twice to ensure the paper's accountability, and a total of 222 articles were identified. In the next stage, the panel member shared the short-listed articles. After that, the panel member was eliminated because it focused only on the SCW mechanism behavior, non-waste application, or failure to find key elements; then the article came to 140. After that, panel members started to fully text analyze and eliminate articles that are not explicitly focused on supercritical water gasification or oxidation (SCWG/SCWO), instead focusing on the behavior or mechanism of SCW, and finally 120 articles were selected for the systematic review, which primarily focus on SCWO and SCWG with the major core aspects, final number of articles selected was 86 in this review. In the final Stages, the panel recommends studying 86 papers, and the author then developed the research profile for the selected studies. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e depicts the SLR process in a PRISMA diagram.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Data Execution \u0026amp; Research Profiling\u003c/h2\u003e\u003cp\u003eThis section mainly describes the research profile of the pool of studies in the sample. The results presented in this section assess the current research based on the last six years, 2020\u0026ndash;2025. Organizing and summarizing the research profile in a particular domain of knowledge delineates the direction and momentum of the research field. Fig., which presents the time-wise proliferation of research on the interaction of the SCW in waste treatment, the challenges, and the experimental area.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eRecords were identified from Web of Science and Scopus without filtering, just giving the title we found from WoS, n\u0026thinsp;=\u0026thinsp;2463, and from Scopus, n\u0026thinsp;=\u0026thinsp;2442. After setting our inclusion and exclusion criteria from WoS, it comes to 420, and from Scopus, it's 561. The sum of the after filter is 981. Then we checked the duplicated value, we found n\u0026thinsp;=\u0026thinsp;572 duplicates after removing them, and the count comes to 409. Then we started to read the title and abstract to form another n\u0026thinsp;=\u0026thinsp;177 excluded, which mainly excluded because not core related to waste treatment or SCWG /SCWO, not the central core part.\u003c/p\u003e\u003cp\u003eSome are mechanical focus; some are not waste-related. Then we have 232 papers. Then we divided with our panel members, five for complete text analysis; they all excluded in total n\u0026thinsp;=\u0026thinsp;115, the main reason was the HTL (Hydrothermal Liquefaction) pathway, not SCWG/SCWO. Then we rechecked and tried to download all the PDFs we could not retrieve \u0026mdash; 16 PDFs \u0026mdash; and excluded 15 more. And finally, in our systematic review, we selected 86 studies.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the distribution of publications over six years, clearly showing an emerging topic in the modern world. From 2020 to 2025, it showed some variability, while from 2023 to 2025, it showed the highest number of publications, which indicates the current emerging solution and work in SCWG and SCWO. These trends suggest that this topic has gained attention from the scientific community.\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\u003eNumber of included articles by journal (n\u0026thinsp;=\u0026thinsp;86)\u003c/p\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=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRank\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChemical Engineering Journal\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal of Water Process Engineering\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEnergy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal of Environmental Chemical Engineering\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal of Cleaner Production\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWater Research\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal of Hazardous Materials\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eChemosphere\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBiomass and Bioenergy\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProcess Safety and Environmental Protection\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal of Environmental Management\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e\u003cp\u003e7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInternational Journal of Environmental Science and Technology\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eApplication of Supercritical Water Oxidation to Effectively Destroy Per- and Polyfluoroalkyl Substances in Aqueous Matrices\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWater\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eJournal of Chemical Technology \u0026amp; Biotechnology\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOthers with one article\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e16\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\u003eIt is evident in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e that a few journals that are highly concentrated on SCWO and SCWG in waste treatment, such as J Water Process, Chem Eng J, and Energy, dominate the field. At the same time, many others have only one or two publications, which indicate limited research diversity and highlight the scope of the work.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eIntegration of Supercritical Water Gasification (SCWG) and Supercritical Water Oxidation (SCWO) for Sustainable Wastewater Treatment and Energy Recovery: SCWO and SCWG achieved destruction of hazardous waste but also for energy recovery though energy demand to running operation and clogging remain unsolved.\u003c/p\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Core concept\u003c/h2\u003e\u003cp\u003eIn the current industrialized society, waste is not just a source of pollution but a source of energy. Supercritical Water Oxidation and Supercritical Water Gasification are two SCW technologies based on the principle of physics, which occur when water exceeds its critical point (374 \u0026deg; C, 22.1 MPa). It has the characteristics of liquid and gas. In this situation, organic waste and contaminants are quickly broken down, resulting in the complete oxidation of the SCWO and partial gases in SCWG. Therefore, these two processes can be seen together as a circular waste-to-energy technology where it is possible to refine water, reduce contamination, and restore energy from waste.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Technological Progress\u003c/h2\u003e\u003cp\u003eAccording to Ma et al. [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] it is possible to remove 99% Cr (Chromium) and \u0026gt;\u0026thinsp;99.9% TOC by a combination of SCWO and ultrasonic, which is an important achievement in solid waste reproduction. As illustrated through simulation, auto thermal operation and 78.95% energy recovery efficiency can be achieved; SCWO can be an energy-positive wastewater [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Another significant achievement showed by Chen et al. [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] is that mixed plastic SCWG achieved 106.8% GE and H₂ yield 15.1 mol/kg H\u003csub\u003e2\u003c/sub\u003e yield, which is higher than single plastic due to synergistic effects [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e], using K₂CO₃/H₂O₂ catalyst, have achieved 15.5 mol/kg H₂ yield using catalysts and have proven that catalysts accelerate WGSR (Water-Gas-Shift-Reaction). Fedyaeva et al. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] highlighted that energy consumption has reduced by 1.3\u0026ndash;1.5 times through the addition of methane, although salt precipitation and corrosion remain unsolved. Mour\u0026atilde;o et al. [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e] showed that 74.74\u0026ndash;98.8% carbon conversion and H\u003csub\u003e2\u003c/sub\u003e yield of 2.18 mol/Mol C are available by SCWG in the biodiesel industry [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] and achieved an H₂ 72.4% from textile waste and a gasification efficiency of 72.4%.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Environmental \u0026amp; Energy Relevance\u003c/h2\u003e\u003cp\u003eIt provides a combined analysis of these studies that SCWO waste almost entirely eliminates organic and heavy metal contamination (TOC and COD removal\u0026thinsp;\u0026gt;\u0026thinsp;99%). In the SCWG process, it is possible to convert the wastewater into an energy source, where H₂ yield is between 2.18\u0026ndash;15.5 mol/kg.AI-Integrated Optimization. Ma et al. [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] Proven that a data-driven model can improve these processes. In real tests [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] a heat recovery efficiency\u0026thinsp;\u0026asymp;\u0026thinsp;79% and 674.26 W thermal output were found in simulation, which gives direction of an energy-positive system.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.4. Restrictions and Challenges\u003c/h2\u003e\u003cp\u003eThere are some serious problems in reimplementing these technologies such as catalyst deactivation and fouling - carbon and salt deposits disable the catalyst [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Also, salt precipitation and reactor corrosion, metal damage, and clogging are major problems at high temperatures[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Feedstock diversity limitation - most research is limited to a single [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. AI and simulation model limitation - yet single objective [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Industrial Scalability - Most studies are limited to the laboratory or Aspen Plus simulation level [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Life Cycle and Economic Analysis deficit - practical cost and environmental impact are not completely analyzed.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Future Research Directions","content":"\u003cp\u003eImproving the life span of the catalyst and enhancing the regeneration process, as well as corrosion-resistant alloy and self-cleaning reactor design. However, hybrid process integration with SCWG and SCWO provides a new feasibility in waste treatment; the current focus should be on AI-based multi-objective optimization (H₂ yield, exergy, CO₂ minimization); Pilot-scale continuous reactor validation. Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA) should also be explored. SCWO and SCWG are two complementary processes of wastewater treatment. SCWO reduces environmental pollution, whereas SCWG produces energy from the process. Both combinedly produce a Zero Waste and Energy-Positive Circular Wastewater System, but for successful implementation in the industrial field, materials stability, salt control, and multi-optimization techniques\u0026rsquo; reliability, and also more research is needed. A promising approach to sustainable wastewater treatment is the combination of SCWG and SCWO, which allows for both energy recovery and pollutant elimination at the same time. To attain a circular, energy-positive future, integrated process modeling, material innovation, and pilot-scale validation are necessary to overcome the remaining significant obstacles of catalyst deactivation, corrosion, and limited scalability.\u003c/p\u003e"},{"header":"5. Scale Up Challenges","content":"\u003cp\u003eThe systematic review of recent studies between 2020\u0026ndash;2025 based on SCWG and SCWOIO is proof that large-scale studies have not been fully explored due to engineering and operational constraints. Fouling, catalyst positioning, and reduced lifetime innovation, such as ultrasonic descaling and modular heater design, are mostly caused by salt precipitation and corrosion [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. Although due to salt recovery modeling by [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e] and co-fuel assisted operation [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], their performance has been improved on a short-term basis, their long-term performance is still unproven. Economic viability is often limited due to energy demand and autothermal inefficiency. Current CFD modeling, hybrid reactor design, and energy interaction [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e] optimization show a promising future, but they mostly remain theoretical. Therefore, the future work should still maintain its research focus on how to make the industrial-scale operation of SCWG and SCWO in waste treatment more sustainable.\u003c/p\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e5.1 Precipitation of salt and Plugging\u003c/h2\u003e\u003cp\u003eSalt precipitation is a basic limitation for continuous SCWG and SCWO operation. Recently, a salt nucleation model that achieved 69% Na/K carbonate recovery [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e] and modular heater designs with ultrasonic descaling for salt formation reduction [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e] were developed. But still, wall fouling and corrosion are persistent, and ultrasonic descaling is not industrially validated. To improve operational stability, Future research should focus more on pre-nucleation salt separation, salt-tolerant materials such as Inconel 740H and Hastelloy C-276, and self-cleaning continuous reactors.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e5.2 Corrosion and Degradation of metal\u003c/h2\u003e\u003cp\u003eLongevity of reactor and its performance is significantly affected by corrosion. In hot zones, Na/K carbonate corrosion rates were three times higher [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e], and Monel 400 ejectors with cooling sprays were used to reduce corrosion [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e]. On the other hand, KOH additives delayed scaling but increased corrosion [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. Nonetheless, no anti-corrosive coating has been validated that exceeds 1000 hours, and chloride oxygen synergistic corrosion remains unresolved. To minimize oxidation stress, future work should focus more on coated alloy liners, in reactor corrosion monitoring sensors, and optimized O\u003csub\u003e2\u003c/sub\u003e injections.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e5.3 Reactor Design and Flow Management:\u003c/h2\u003e\u003cp\u003eFor continuous operation, efficient reactor design is a must. CFD-thermodynamic modeling is used to identify hot-spot flow zones [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e], and modular multi-point heaters reduce thermal stress [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. To demonstrate operational stability, a 90-minute continuous run was performed; to run operational stability [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], however, continuous operation remains limited to \u0026le;\u0026thinsp;2 hours due to flow mal-distribution and incomplete oxidation. So future studies should apply multiphase CFD optimization, explore fluidized-bed salt-tolerant reactors, and scale up to 1000-hour pilot tests using real feed stocks.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e5.4 Energy Demand and Autothermal Operation\u003c/h2\u003e\u003cp\u003eHigh energy demand is still a major limitation. Ethanol-assisted SCWO achieved near-autothermal performance [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e], while methane co-fuel addition reduced heating load by 1.5 times [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. While simulation modeling minimized requirements for utilities up to 60% [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e], full auto thermal operation has not been achievable. Corrosion is often increased by co-fuel injections, and renewable energy integration remains limited. For efficiency improvement, future studies should focus more on development of co-fuel systems with waste heat recovery and exploration of hybrid SCWG-SCWO configurations.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e5.5 Catalyst Deactivation and Stability\u003c/h2\u003e\u003cp\u003eDue to catalyst degradation, long-term operation is often hindered. Catalysts which are Ru-based show high performance but are costly [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e], while Ni catalysts are prone to sulfur and chlorine poisoning [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Although KOH catalysts achieved 99% transformation, they suffered from leaching [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The short lifespan and the catalyst\u0026rsquo;s high cost remain an unresolved problem. So future works should focus on investigating Ni-Mo-Fe bimetallic catalysts, in-situ regeneration, and hybrid alkali-metal catalysts to enhance stability and reduce costs.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e5.6 Effluent Quality and Toxic materials\u003c/h2\u003e\u003cp\u003eAlthough SCWG and SCWO can demonstrate high degradation efficiency, residual toxicity always remains an issue. [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e] achieved 85% COD removal in his research, but pyridines and quinolines remained. Similarly, Peng et al. [\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e] discovered that PAHs contamination slowly occurs in the oily wastewater. Persistent PAHs, phenolics, and nitrogen compounds exhibit limited treatment, totality, and ecotoxicity testing. However, some serious problems can be witnessed at the time of reimplementing these technologies: Catalyst deactivation and fouling - carbon and salt deposits are used to disable the catalyst [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e"},{"header":"6. Conclusion and Recommendations","content":"\u003cp\u003eWaste generation from multiple feedstocks is omnipresent and has emerged as a global concern and crucial topic in energy recovery and waste destruction by SCW technologies. SCWO and SCWG methods have been effectively used for the treatment of various wastes such as sewage sludge, oily sludge, industrial waste, animal waste, biomass, and pharmaceutical residues with energy recovery. High levels of Carbon efficiency (90\u0026ndash;99%) and pollutant removal efficiencies (99.9%) with energy recovery and production of Syngas have been found. The objective of this review was to highlight the current scenario of SCWG and SCWO in waste treatment. The findings of this paper suggest that SCWO and SCWG are more effective in waste treatment, such as 99.99% destruction of organic compounds and energy recovery. The paper also identified the central issue still unsolved and discussed the scale-up challenges in waste treatment, the operational cost, and the high energy demand to operate SCW technologies. The result of this study has significant implications, indicating that there is a high time to undertake necessary steps to integrate SCWG and SCWO in hazardous waste treatment as well as energy recovery with low cost and without catalysts.\u003c/p\u003e\u003cp\u003eFuture research should focus on developing low-cost and long-life Ni-Fe-Mo-based hybrid catalysts, real-time salt separation systems, and renewable auto-thermal reactor designs. Moreover, to evaluate environmental and economic feasibility, focus should be on comprehensive Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA), with coupling SCWG and SCWO in waste treatment to enhance waste treatment efficiency. SCW technology can perform better if the energy demand can be reduced.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors have read, understood, and have complied as applicable with the statement on \u0026ldquo;Ethical responsibilities of Authors\u0026rdquo; as found in the Instructions for Authors. This is to certify that this paper is an original academic work. The authors declare that all the ethical standards applicable to \u0026ldquo;Waste and Biomass Valorization\u0026rdquo; have been complied with.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe want to thank our committed team members for their invaluable support during this project. We also extend heartfelt thanks to Mayesha Farzana Mumu, studying MBBS in Sylhet Women\u0026rsquo;s Medical College, for her constant support and encouragement throughout this research journey.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo data was used for the research described in the article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis review was carried out independently and did not receive any financial aid.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eWang L et al (Mar. 2025) Experimental study on supercritical water gasification of grease trap sludge in a continuous reactor. Biomass Bioenergy 194:107636. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.biombioe.2025.107636\u003c/span\u003e\u003cspan address=\"10.1016/j.biombioe.2025.107636\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen Y, He Y, Jin H, Guo L (Apr. 2020) Resource utilization of landfill leachate gasification in supercritical water. Chem Eng J 386:124017. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2020.124017\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2020.124017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDu M, Liu S, Sun J, Jin H, Chen Y, Guo L (2023) \u0026lsquo;Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts\u0026rsquo;, \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e, vol. 420, p. 138455, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2023.138455\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2023.138455\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAdar E, Ince M, Bilgili MS (2020) \u0026lsquo;Characteristics of Liquid Products in Supercritical Water Gasification of Municipal Sewage Sludge by Continuous Flow Tubular Reactor\u0026rsquo;, \u003cem\u003eWaste Biomass Valorization\u003c/em\u003e, vol. 11, no. 11, pp. 6321\u0026ndash;6335, Nov. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s12649-019-00858-9\u003c/span\u003e\u003cspan address=\"10.1007/s12649-019-00858-9\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMylapilli SVP, Reddy SN (May 2022) Catalytic and non-catalytic degradation of acetaminophen in supercritical water. Environ Res 207:112191. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.envres.2021.112191\u003c/span\u003e\u003cspan address=\"10.1016/j.envres.2021.112191\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRosansky S et al (2024) \u0026lsquo;Field Demonstration of PFAS Destruction in Various Alcohol-Resistant AFFFs Using Supercritical Water Oxidation (SCWO)\u0026rsquo;, \u003cem\u003eACS EST Water\u003c/em\u003e, vol. 4, no. 10, pp. 4486\u0026ndash;4496, Oct. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1021/acsestwater.4c00499\u003c/span\u003e\u003cspan address=\"10.1021/acsestwater.4c00499\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWebb H et al (Nov. 2025) PFAS destruction using supercritical water oxidation (SCWO) at Peterson Space Force Base. J Hazard Mater Lett 6:100156. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.hazl.2025.100156\u003c/span\u003e\u003cspan address=\"10.1016/j.hazl.2025.100156\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen Y, Yi L, Li S, Yin J, Jin H (May 2020) Catalytic gasification of sewage sludge in near and supercritical water with different catalysts. Chem Eng J 388:124292. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2020.124292\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2020.124292\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDu M, Liu S, Sun J, Jin H, Chen Y, Guo L (2023) \u0026lsquo;Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts\u0026rsquo;, \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e, vol. 420, p. 138455, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2023.138455\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2023.138455\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCui J, Wang H, Hantoko D, Wen X, Kanchanatip E, Yan M (Oct. 2023) Nitrogen and phosphorus recovery from sludge treatment by supercritical water gasification coupled with struvite crystallization. J Water Process Eng 55:104070. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2023.104070\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2023.104070\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCheng J, Nouri Gehraz SA, Khodamoradi S, Jani Qali D, Jasim DJ (Nov. 2024) H2-rich gas production from gasification of oily sludge via supercritical water technology: Synergy effect of KOH, K2CO3, and reaction parameters. Chem Eng Process - Process Intensif 205:110008. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cep.2024.110008\u003c/span\u003e\u003cspan address=\"10.1016/j.cep.2024.110008\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCui J, Wang H, Hantoko D, Wen X, Kanchanatip E, Yan M (Oct. 2023) Nitrogen and phosphorus recovery from sludge treatment by supercritical water gasification coupled with struvite crystallization. J Water Process Eng 55:104070. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2023.104070\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2023.104070\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang Y, Zhang S, Li H, Wang C, Jiang F, Lyu J (2020) \u0026lsquo;Treatment of municipal sludge by hydrothermal oxidation process with H2O2\u0026rsquo;, \u003cem\u003eChemosphere\u003c/em\u003e, vol. 257, p. 127140, Oct. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.chemosphere.2020.127140\u003c/span\u003e\u003cspan address=\"10.1016/j.chemosphere.2020.127140\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFedyaeva ON, Morozov SV, Vostrikov AA (2021) \u0026lsquo;Supercritical water oxidation of chlorinated waste from pulp and paper mill\u0026rsquo;, \u003cem\u003eChemosphere\u003c/em\u003e, vol. 283, p. 131239, Nov. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.chemosphere.2021.131239\u003c/span\u003e\u003cspan address=\"10.1016/j.chemosphere.2021.131239\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHu Y et al (2021) \u0026lsquo;CO2-assisted catalytic municipal sludge for carbonaceous biofuel via sub- and supercritical water gasification\u0026rsquo;, \u003cem\u003eEnergy\u003c/em\u003e, vol. 233, p. 121184, Oct. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.energy.2021.121184\u003c/span\u003e\u003cspan address=\"10.1016/j.energy.2021.121184\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLu L et al (Jan. 2025) Mechanism of salt deposition, nucleation and separation in the supercritical water gasification of black liquor. Chem Eng J 506:159914. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2025.159914\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2025.159914\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWang L et al (Mar. 2025) Experimental study on supercritical water gasification of grease trap sludge in a continuous reactor. Biomass Bioenergy 194:107636. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.biombioe.2025.107636\u003c/span\u003e\u003cspan address=\"10.1016/j.biombioe.2025.107636\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa M, Zhang S, Chen Y, Chen B, Guo L (Oct. 2024) Optimization of hydrogen-rich syngas from coal and sewage sludge co-gasification in supercritical water. Chem Eng J 497:154792. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2024.154792\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2024.154792\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFedyaeva ON, Alekhin SA, Morozov SV, Vostrikov AA (2024) \u0026lsquo;Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode\u0026rsquo;, \u003cem\u003eBiomass Bioenergy\u003c/em\u003e, vol. 188, p. 107324, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.biombioe.2024.107324\u003c/span\u003e\u003cspan address=\"10.1016/j.biombioe.2024.107324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi G, Niu M, Chen Y (Jan. 2025) Experimental and kinetic modeling study of oxidative degradation of benzene and phenol in supercritical water. J Environ Manage 373:123992. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jenvman.2024.123992\u003c/span\u003e\u003cspan address=\"10.1016/j.jenvman.2024.123992\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu S, Ge Z, Du M, Guo L (Jan. 2023) Supercritical water partial oxidation of indole: Reaction variables, migration pathways, and nitrogen distribution. Chem Eng J 451:138638. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2022.138638\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2022.138638\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePeng Z et al (Jul. 2023) Clean treatment and resource utilization of oilfield wastewater using supercritical water gasification. J Clean Prod 411:137239. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2023.137239\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2023.137239\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eQiu Y, Liu Y, Zhang F, Rong W (2024) \u0026lsquo;Thermodynamic and exergy assessments of supercritical water gasification of oily sludge assisted by hydrothermal flame\u0026rsquo;, \u003cem\u003eEnergy\u003c/em\u003e, vol. 296, p. 131212, Jun. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.energy.2024.131212\u003c/span\u003e\u003cspan address=\"10.1016/j.energy.2024.131212\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYan M, Hantoko D, Kanchanatip E, Zheng R, Zhong Y, Mubeen I (2020) \u0026lsquo;Valorization of sewage sludge through catalytic sub- and supercritical water gasification\u0026rsquo;, \u003cem\u003eJ. Energy Inst.\u003c/em\u003e, vol. 93, no. 4, pp. 1419\u0026ndash;1427, Aug. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.joei.2020.01.004\u003c/span\u003e\u003cspan address=\"10.1016/j.joei.2020.01.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLuo C, Fan X, Tang S, Xi H (Sep. 2025) Comparative study of alcohol co-oxidation for enhanced phenol degradation in wastewater under supercritical water oxidation (SCWO) conditions. J Water Process Eng 77:108477. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2025.108477\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2025.108477\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen Y, He Y, Jin H, Guo L (Apr. 2020) Resource utilization of landfill leachate gasification in supercritical water. Chem Eng J 386:124017. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2020.124017\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2020.124017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDu M, Liu S, Sun J, Jin H, Chen Y, Guo L (2023) \u0026lsquo;Clean conversion of pig manure via supercritical water gasification: Hydrogen-enriched syngas generation, mechanisms analysis, and environmental impacts\u0026rsquo;, \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e, vol. 420, p. 138455, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2023.138455\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2023.138455\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi Y et al (Jun. 2024) Supercritical water oxidation for the treatment and utilization of organic wastes: Factor effects, reaction enhancement, and novel process. Environ Res 251:118571. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.envres.2024.118571\u003c/span\u003e\u003cspan address=\"10.1016/j.envres.2024.118571\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang H et al (May 2020) Alkali-catalyzed supercritical water gasification of sewage sludge: effect of liquid residue reuse as homogenous catalyst. Int J Environ Sci Technol 17(5):2845\u0026ndash;2852. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1007/s13762-020-02697-x\u003c/span\u003e\u003cspan address=\"10.1007/s13762-020-02697-x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi L, Peng P, Wang G, Li X, Cao W, Gong Z (2025) \u0026lsquo;Study on the gasification mechanisms of key intermediates of oily sludge in supercritical water by ReaxFF-MD method\u0026rsquo;, \u003cem\u003eEnergy\u003c/em\u003e, vol. 330, p. 136907, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.energy.2025.136907\u003c/span\u003e\u003cspan address=\"10.1016/j.energy.2025.136907\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePeng Z et al (Jul. 2023) Clean treatment and resource utilization of oilfield wastewater using supercritical water gasification. J Clean Prod 411:137239. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2023.137239\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2023.137239\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFedyaeva ON, Alekhin SA, Morozov SV, Vostrikov AA (2024) \u0026lsquo;Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode\u0026rsquo;, \u003cem\u003eBiomass Bioenergy\u003c/em\u003e, vol. 188, p. 107324, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.biombioe.2024.107324\u003c/span\u003e\u003cspan address=\"10.1016/j.biombioe.2024.107324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRosansky S et al (2024) \u0026lsquo;Field Demonstration of PFAS Destruction in Various Alcohol-Resistant AFFFs Using Supercritical Water Oxidation (SCWO)\u0026rsquo;, \u003cem\u003eACS EST Water\u003c/em\u003e, vol. 4, no. 10, pp. 4486\u0026ndash;4496, Oct. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1021/acsestwater.4c00499\u003c/span\u003e\u003cspan address=\"10.1021/acsestwater.4c00499\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhang H, Wang C, Zhang X, Zhang R, Ding L (2020) \u0026lsquo;Formation and inhibition of polycyclic aromatic hydrocarbons from the gasification of cyanobacterial biomass in supercritical water\u0026rsquo;, \u003cem\u003eChemosphere\u003c/em\u003e, vol. 253, p. 126777, Aug. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.chemosphere.2020.126777\u003c/span\u003e\u003cspan address=\"10.1016/j.chemosphere.2020.126777\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHina M, Chauhan C, Kaur P, Kraus S, Dhir A (Jan. 2022) Drivers and barriers of circular economy business models: Where we are now, and where we are heading. J Clean Prod 333:130049. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2021.130049\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2021.130049\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKushwah S, Dhir A, Sagar M, Gupta B (2019) \u0026lsquo;Determinants of organic food consumption. A systematic literature review on motives and barriers\u0026rsquo;, \u003cem\u003eAppetite\u003c/em\u003e, vol. 143, p. 104402, Dec. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.appet.2019.104402\u003c/span\u003e\u003cspan address=\"10.1016/j.appet.2019.104402\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa H, Li X, Zhu C, Chen F, Yang Y, Chen X (2020) \u0026lsquo;Liberation and recovery of Cr from real tannery sludge by ultrasound-assisted supercritical water oxidation treatment\u0026rsquo;, \u003cem\u003eJ. Clean. Prod.\u003c/em\u003e, vol. 267, p. 122064, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jclepro.2020.122064\u003c/span\u003e\u003cspan address=\"10.1016/j.jclepro.2020.122064\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRuya PM, Purwadi R, Lim SS (Feb. 2020) Supercritical water gasification of sewage sludge for power generation\u0026ndash; thermodynamic study on auto-thermal operation using Aspen Plus. Energy Convers Manag 206:112458. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.enconman.2019.112458\u003c/span\u003e\u003cspan address=\"10.1016/j.enconman.2019.112458\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLuo C, Teng S, Wang J, Xi H (Jan. 2024) Energy yield from wastewater by supercritical water oxidation process: Experimental validation and simulation from the viewpoint of energy system. Energy Convers Manag 299:117876. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.enconman.2023.117876\u003c/span\u003e\u003cspan address=\"10.1016/j.enconman.2023.117876\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen Y, Yi L, Wei W, Jin H, Guo L (2022) \u0026lsquo;Hydrogen production by sewage sludge gasification in supercritical water with high heating rate batch reactor\u0026rsquo;, \u003cem\u003eEnergy\u003c/em\u003e, vol. 238, p. 121740, Jan. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.energy.2021.121740\u003c/span\u003e\u003cspan address=\"10.1016/j.energy.2021.121740\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGong W et al (2023) Sep., \u0026lsquo;Catalytic gasification of textile wastewater treatment sludge for hydrogen production in supercritical water with K2CO3/H2O2: Reaction variables, mechanism and kinetics\u0026rsquo;, \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e, vol. 48, no. 78, pp. 30310\u0026ndash;30322. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijhydene.2023.04.160\u003c/span\u003e\u003cspan address=\"10.1016/j.ijhydene.2023.04.160\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMour\u0026atilde;o LC et al (Apr. 2025) Continuous hydrogen production from biodiesel wastewater treatment via supercritical water gasification. Int J Hydrog Energy 116:486\u0026ndash;496. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijhydene.2025.03.068\u003c/span\u003e\u003cspan address=\"10.1016/j.ijhydene.2025.03.068\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eThanikodi S, Sagade AA (2024) \u0026lsquo;Utilizing supercritical water gasification for hydrogen production combined with a waste heat recovery system for domestic households\u0026rsquo;, \u003cem\u003eResults Eng.\u003c/em\u003e, vol. 24, p. 103432, Dec. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.rineng.2024.103432\u003c/span\u003e\u003cspan address=\"10.1016/j.rineng.2024.103432\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa Z, Wang J, Feng Y, Wang R, Zhao Z, Chen H (2023) \u0026lsquo;Supercritical water gasification of organic solid waste: H2 yield and cold gas efficiency optimization considering modeling uncertainties\u0026rsquo;, \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e, vol. 48, no. 79, pp. 30702\u0026ndash;30717, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijhydene.2023.04.268\u003c/span\u003e\u003cspan address=\"10.1016/j.ijhydene.2023.04.268\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFedyaeva ON, Alekhin SA, Morozov SV, Vostrikov AA (2024) \u0026lsquo;Effect of methane addition on supercritical water oxidation of poultry manure in the flow mode\u0026rsquo;, \u003cem\u003eBiomass Bioenergy\u003c/em\u003e, vol. 188, p. 107324, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.biombioe.2024.107324\u003c/span\u003e\u003cspan address=\"10.1016/j.biombioe.2024.107324\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGong M, Chu H, Xu Q (Apr. 2024) Influences of reaction parameters and complexation pretreatments on the distribution of phosphorus during hydrothermal carbonization of dewatered sewage sludge. J Water Process Eng 60:105209. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2024.105209\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2024.105209\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen J, Fu L, Tian M, Kang S (2022) and J. E, \u0026lsquo;Comparison and synergistic effect analysis on supercritical water gasification of waste thermoplastic plastics based on orthogonal experiments\u0026rsquo;, \u003cem\u003eEnergy\u003c/em\u003e, vol. 261, p. 125104, Dec. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.energy.2022.125104\u003c/span\u003e\u003cspan address=\"10.1016/j.energy.2022.125104\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMour\u0026atilde;o LC et al (Apr. 2025) Continuous hydrogen production from biodiesel wastewater treatment via supercritical water gasification. Int J Hydrog Energy 116:486\u0026ndash;496. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijhydene.2025.03.068\u003c/span\u003e\u003cspan address=\"10.1016/j.ijhydene.2025.03.068\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMa Z, Wang J, Feng Y, Wang R, Zhao Z, Chen H (2023) \u0026lsquo;Supercritical water gasification of organic solid waste: H2 yield and cold gas efficiency optimization considering modeling uncertainties\u0026rsquo;, \u003cem\u003eInt. J. Hydrog. Energy\u003c/em\u003e, vol. 48, no. 79, pp. 30702\u0026ndash;30717, Sep. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ijhydene.2023.04.268\u003c/span\u003e\u003cspan address=\"10.1016/j.ijhydene.2023.04.268\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang J, Xie S, Wang S (Jun. 2024) Safety Management and Accident-Control Strategy for a Commercial-Scale Plant for Supercritical Water Oxidation of Sludge. Appl Sci 14(12):5101. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/app14125101\u003c/span\u003e\u003cspan address=\"10.3390/app14125101\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLu L et al (Jan. 2025) Mechanism of salt deposition, nucleation and separation in the supercritical water gasification of black liquor. Chem Eng J 506:159914. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2025.159914\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2025.159914\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePereira MB et al (2023) \u0026lsquo;Continuous Treatment of Refractory Wastewater from Research and Teaching Laboratories via Supercritical Water Oxidation\u0026ndash;Experimental Results and Modeling\u0026rsquo;, \u003cem\u003eWater\u003c/em\u003e, vol. 15, no. 22, p. 3926, Nov. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/w15223926\u003c/span\u003e\u003cspan address=\"10.3390/w15223926\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang C, Jiang Z, Wang S, Chen H, Zhang J, Li Y (Jan. 2025) Supercritical water oxidation of oily sludge: Operating parameters\u0026rsquo; effects and reaction kinetics. J Water Process Eng 69:106871. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2024.106871\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2024.106871\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChen Y, He Y, Jin H, Guo L (Apr. 2020) Resource utilization of landfill leachate gasification in supercritical water. Chem Eng J 386:124017. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.cej.2020.124017\u003c/span\u003e\u003cspan address=\"10.1016/j.cej.2020.124017\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang C, Jiang Z, Wang S, Chen H, Zhang J, Li Y (Jan. 2025) Supercritical water oxidation of oily sludge: Operating parameters\u0026rsquo; effects and reaction kinetics. J Water Process Eng 69:106871. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2024.106871\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2024.106871\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi G, Niu M, Chen Y (Jan. 2025) Experimental and kinetic modeling study of oxidative degradation of benzene and phenol in supercritical water. J Environ Manage 373:123992. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jenvman.2024.123992\u003c/span\u003e\u003cspan address=\"10.1016/j.jenvman.2024.123992\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePereira MB et al (Oct. 2023) Simultaneous recycling of waste solar panels and treatment of persistent organic compounds via supercritical water technology. Environ Pollut 335:122331. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.envpol.2023.122331\u003c/span\u003e\u003cspan address=\"10.1016/j.envpol.2023.122331\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGaliwango E, Butler J, Lotfi S (2024) \u0026lsquo;A Review of Catalyst Integration in Hydrothermal Gasification\u0026rsquo;, \u003cem\u003eFuels\u003c/em\u003e, vol. 5, no. 3, pp. 375\u0026ndash;393, Aug. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.3390/fuels5030022\u003c/span\u003e\u003cspan address=\"10.3390/fuels5030022\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMontesantos N, Skjolding LM, Baun A, Muff J, Maschietti M (Feb. 2023) Reducing the environmental impact of offshore H2S scavenging wastewater via hydrothermal oxidation. Water Res 230:119507. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.watres.2022.119507\u003c/span\u003e\u003cspan address=\"10.1016/j.watres.2022.119507\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePeng P, Wang G, Li L, Ge H, Jin H, Guo L (2023) \u0026lsquo;Experimental investigation on the degradation of polymer-containing oily sludge in sub-/supercritical water\u0026rsquo;, \u003cem\u003eEnergy Sources Part Recovery Util. Environ. Eff.\u003c/em\u003e, vol. 45, no. 1, pp. 1983\u0026ndash;1993, Apr. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1080/15567036.2023.2184001\u003c/span\u003e\u003cspan address=\"10.1080/15567036.2023.2184001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGong M, Chu H, Xu Q (Apr. 2024) Influences of reaction parameters and complexation pretreatments on the distribution of phosphorus during hydrothermal carbonization of dewatered sewage sludge. J Water Process Eng 60:105209. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.jwpe.2024.105209\u003c/span\u003e\u003cspan address=\"10.1016/j.jwpe.2024.105209\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAffolter J, Brunner T, Hagger N, Vogel F (Dec. 2022) A prototype system for the hydrothermal oxidation of feces. Water Res X 17:100160. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.wroa.2022.100160\u003c/span\u003e\u003cspan address=\"10.1016/j.wroa.2022.100160\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNunes LJR (2022) \u0026lsquo;Biomass gasification as an industrial process with effective proof-of-concept: A comprehensive review on technologies, processes and future developments\u0026rsquo;, \u003cem\u003eResults Eng.\u003c/em\u003e, vol. 14, p. 100408, Jun. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.rineng.2022.100408\u003c/span\u003e\u003cspan address=\"10.1016/j.rineng.2022.100408\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"No Fund","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Supercritical water, gasification, oxidation, scale-up, waste treatment","lastPublishedDoi":"10.21203/rs.3.rs-7988523/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7988523/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn recent times, Supercritical Water Gasification (SCWG) and Supercritical Water Oxidation (SCWO) technologies are rapidly advancing as promising solutions for solid \u0026amp; liquid waste management. We conducted a systematic review on various feedstocks (sewage sludge, oily sludge, industrial waste, biomass, animal wastes, and pharmaceutical effluents), using multiple types of catalysts (alkaline, Ni-Mo, Ru-based \u0026amp; hybrid), and the scale-up challenges together. The methodology used in this review paper follows the PRISMA guidelines, including literature search, inclusion and exclusion criteria, and content analysis. The dataset for this systematic review paper solely selects journal articles on either SCWG or SCWO published between 2020 and 2025, resulting in 86 papers after screening and excluding irrelevant ones. The findings underscore the critical need for scalable, durable catalysts and reactor design that will address waste issues. This integration of SCWO and SCWG is highly feasible for destruction and energy recovery from waste. Partial advancements include modular heater design, ultrasonic descaling, autothermal operation using methane and ethanol co-fuel, and salt recovery modelling. It will be possible to take this technology to a sustainable and commercial level through low-cost and long-life catalysts, real-time salt control, and hybrid SCWG-SCWO coupling.\u003c/p\u003e","manuscriptTitle":"Supercritical Water Gasification and Oxidation for Waste Treatment: A Systematic Review of Feedstocks, Catalysts, and Scale-Up Strategies","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-31 05:24:27","doi":"10.21203/rs.3.rs-7988523/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"07490177-ccc3-488f-89d7-673b729dbb48","owner":[],"postedDate":"October 31st, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":57155339,"name":"Environmental Engineering"}],"tags":[],"updatedAt":"2025-10-31T05:24:27+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-31 05:24:27","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7988523","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7988523","identity":"rs-7988523","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}