Long-term carbon dioxide removal potential from the application of wood biochar and basanite rock powder in sandy soil using the LiDELSv2 process-based modeling approach

Abstract The rise in atmospheric carbon dioxide (CO 2 ) concentrations requires scalable and effective carbon dioxide removal (CDR) strategies. pyrogenic carbon capture and storage relies on the pyrolysis of biomass and the non-oxidative use of biochar, e.g. in soils. Enhanced rock weathering (ERW) captures CO 2 by forming dissolved bicarbonate. In addition to CDR, both methods may offer soil improvement as a co-benefit. However, their interaction and combined CDR potential remain largely unexplored. Here, we investigate their individual and combined effects on carbon dynamics in a temperate agricultural soil. Using the process-based LiDELSv2 model calibrated against data from the lysimeter experiment, we simulate 1000 year impacts of applying 4.2 wt% wood biochar, 2 wt% basanite rock powder (RP), their co-application, and co-pyrolyzed material (rock-enhanced biochar, RE-biochar) on soil organic carbon (SOC), net primary production (NPP), net CO 2 ecosystem exchange (NEE), and calcium (Ca 2+ ) leaching in a northern German sandy soil. Biochar alone led to the highest increase in SOC and achieved a modeled NEE of −200 g C ha −1 yr −1 per ton of biochar throughout 1000 years, acting as a long-term carbon sink. Co-application and RE-biochar increased SOC too, but to a lesser extent. Rock powder alone reduced SOC by 7%. Although RP enhanced Ca 2+ leaching, this did not result in net CO 2 removal. Ecosystem respiration and NPP remained stable in the long term. Our results suggest that, when accounting for assumed application rates, biochar is the primary driver of long-term soil-based CDR, while ERW provides only minor co-benefits. This highlights the need to tailor interventions to specific soil and climate conditions.