A techno-economic analysis and life cycle assessment of woody biochar as an additive for orphan well plugging

Well plugging mitigates methane emissions and protects groundwater, yet conventional cement-based methods carry a high carbon footprint. To explore more sustainable alternatives, this study developed a techno-economic analysis (TEA) and cradle-to-gate life cycle assessment (LCA) for an orphan well in Colorado, comparing a baseline cement-plugging scenario to one that integrates woody biochar in both the cement slurry (3% by weight) and spacer plugging fluid (15% by volume). Various thermochemical conversion pathways were evaluated to understand how different biochar properties influence net greenhouse gas emissions. Results indicate that adding 4.2 tonnes of biochar per well increases plugging costs by 2% but can reduce total emissions from 11.4 tonnes CO₂e to as low as 0.64 tonnes CO₂e per well. Further analysis showed that carbon credit revenues (121 USD per tonne)—if appropriately established for biochar’s use in well plugging—could offset this additional cost, making biochar-additive plugging economically competitive under certain market conditions. These findings demonstrate a promising approach for lowering the environmental impact of well decommissioning and transitioning the industry toward more climate-resilient practices.