Assessing GHG Emission Reduction in Biomass-Derived Biochar Production via Slow Pyrolysis: A Cradle-to-gate LCA Approach

Biochar, a potent negative emission technology (NET), sequesters carbon through biomass thermochemical conversion. Despite greenhouse gas (GHG) storage in biochar being well-understood, analyzing GHG emissions during production is challenging due to diverse carbonization methods. We utilized life cycle assessment (LCA) to address this complexity. In a literature survey, we analyzed contemporary biochar LCA studies, extracting GHG data for emission factor (EF) determination. A scenario-specific case study assesses GHG emission reduction in crop residue-derived biochar. Key factors influencing biochar emissions include feedstock type, surplus energy use, and carbonization scale. Biochar contains EFs ranging from −1.10 to 0.68 ton-CO₂e/ton-biochar. The case study demonstrates that biochar total abatements span from −625,775 to −215,712 ton-CO₂e/year (derived from 840,000 ton-crop residue/year). While overall emission reduction relies on GHG storage, carbonization emissions significantly contribute to total emission diversity. The study proposes a meticulous LCA approach for realistic biochar production, crucial for assessing carbon crediting or offsetting schemes.