Economic feasibility of a novel bio-accelerated silicate weathering reactor concept for climate change mitigation

Abstract

Decarbonization of anthropogenic activities is critical to limit global warming. Enhanced silicate weathering (ESW) is a promising negative emission technology that permanently removes CO₂ through chemical reactions between silicates and water. However, traditional ex-situ processes are often cost-prohibitive, and in-situ approaches face challenges related to monitoring, leakage risks, and slow kinetics. Recent research indicates that biota (e.g., bacteria, fungi, earthworms) can enhance weathering rates, but the synergistic potential of multiple biota types remains underexplored. This study evaluates the techno-economic potential of a novel bioreactor concept that integrates multiple biota types with silicates, water and a CO₂ source to bio-accelerate CO₂ sequestration under milder, lower cost conditions. A prospective techno-economic assessment was conducted for three feedstock scenarios: 1) basalt and straw, 2) diabase and biochar and 3) steel slag and biochar, using Germany as a representative industrial case. For each scenario, the maximum economically viable rock use was determined relative to the European Emission Trading System (ETS) price of 90 €/tCO₂, and minimum sequestration target capacities were identified. Results indicate that the steel slag and biochar scenario is the most favorable, requiring a minimum sequestration capacity of 415 kgCO₂/t rock. Sensitivity analysis highlighted the CO₂ sequestration capacity, rock usage, feedstock cost, and transport logistics as key cost drivers. This study addresses an identified gap in techno-economic assessments of biologically assisted weathering systems and provides development targets for future optimization. The findings suggest that biota-assisted ESW reactors could offer a viable pathway for scalable and economically competitive CO₂ removal.