Biogeochemical Pathways of Carbon Biomineralization in Arboreal and Edaphic Systems

Biomineralization processes in terrestrial ecosystems facilitate durable carbon dioxide removal (CDR) by transforming atmospheric CO₂ into stable inorganic phases via interconnected biogeochemical pathways. This review elucidates the oxalate–carbonate pathway (OCP), wherein oxalogenic angiosperms biosynthesize calcium oxalate (CaC₂O₄) crystals, metabolized by rhizospheric oxalotrophs through oxalyl-CoA decarboxylase (oxc/frc)-mediated decarboxylation, generating alkalinity and bicarbonate for pedogenic CaCO₃ precipitation. Complementary mechanisms include microbially induced carbonate precipitation (MICP) via ureolysis (ureC), denitrification, sulfate reduction, and cyanobacterial photosynthetic CO₂ drawdown, nucleating calcite polymorphs with extracellular carbonic anhydrase catalysis; phytolith-occluded organic carbon (PhytOC) encapsulation in amorphous SiO₂ matrices exhibiting millennial recalcitrance; and enhanced rock weathering (ERW) accelerating silicate (e.g., basalt) dissolution to liberate Ca²⁺/Mg²⁺ for secondary carbonates. Empirical δ¹³C, radiocarbon, and clumped isotope (∆₄₇) analyses from iroko and basaltic fig systems quantify sequestration rates of 0.5–5 t CO₂ ha⁻¹ yr⁻¹, with permanence spanning 10³–10⁶ years. Proposed monitoring, reporting, and verification (MRV) frameworks integrate mineralogical speciation, functional metagenomics, and biomarkers to ensure additionality and mitigate risks. Translational strategies—agroforestry, microbial augmentation, ERW integration—harness co-benefits for edaphic fertility and biodiversity, positioning biomineralization as a gigaton-scale CDR paradigm bridging biogenic transience with geological stability.