Carbon dioxide removal through biochar and enhanced weathering: towards a scalable process-based modelling approach

The combined application of pyrogenic carbon (biochar) and silicate rock minerals (Enhanced Rock Weathering, or ERW) represents a promising integrated strategy for carbon dioxide removal (CDR). However, the effectiveness of these measures is governed by site-specific interactions among soil physical properties, microbial activity, and vegetation processes. To address this challenge, we developed LiDELS (LiBry–DETECT Layer Scheme), a process-based one-dimensional ecosystem model that couples vertical soil water and energy dynamics with vegetation carbon assimilation, soil CO₂ production and transport, and drivers of mineral weathering.

Initial validation and millennial-scale simulations for a sandy soil profile under temperate climate conditions indicate that co-application effects are locally dominated by biochar. Solo biochar application produces the largest and most persistent increases in total and non-pyrogenic soil organic carbon (SOC) and sustains a moderate net CO₂ sink over 1,000 years. In contrast, silicate rock (basanite) application alone yields only a small additional inorganic CDR flux via Ca²⁺ leaching, without substantially improving net ecosystem exchange (NEE) relative to the Control. Co-application of biochar and basanite and the use of rock-enhanced biochar (co-pyrolysed biomass with basanite) lead to intermediate trajectories in SOC and NEE that clearly exceed those of basanite alone, but do not surpass the CDR efficiency of sole biochar, even when evaluated over millennial timescales. These results suggest that in temperate, water-limited, coarse-textured soils, CDR benefits are primarily driven by organic carbon pathways and their positive feedbacks on vegetation productivity. The relative contribution of inorganic CDR pathways is expected to increase under warmer and more humid climatic conditions, where mineral weathering and bicarbonate export are accelerated. 

Building on these site-scale results, ongoing work focuses on upscaling LiDELS to identify regional CDR “hotspots” and find which combinations of soil properties, mineralogy, and climate maximize amendment efficiency.