Pyrogenic and Mineral Carbon Capture and Storage (PyMiCCS)

Biochar and enhanced rock weathering are the two most scalable land-based CDR methods. PyMiCCS combines them into one intervention - co-pyrolysing biomass with silicate rock powder or co-applying both to soil - unlocking synergies in carbon removal, soil restoration, and nutrient supply that neither achieves alone.

PyCCS sequesters atmospheric carbon as pyrogenic carbon in soil. Enhanced rock weathering sequesters it as dissolved bicarbonate through the chemical breakdown of silicate minerals. Both methods work on agricultural land, both improve soil fertility, and both scale with available biomass and rock. PyMiCCS - a concept coined by the Ithaka Institute - combines them, either by co-pyrolysing biomass with rock powder to produce a single rock-enhanced biochar, or by co-applying biochar and rock powder to the same soil.

The combination is not additive - it is synergistic. Biochar raises soil CO₂ concentrations through its effect on microbial activity, accelerating the acid attack on mineral surfaces that drives weathering. Rock powder supplies the base cations that stabilise biochar-derived dissolved organic carbon and buffer the soil acidification caused by biomass export. On base-poor tropical soils - Ferralsols, Acrisols, Nitisols - where natural mineral re-supply is slowest and agricultural degradation most severe, the combined intervention addresses carbon removal, nutrient depletion, and soil acidity in a single pass.

The first experimental results confirm the logic. Meyer zu Drewer et al. (2025) showed that co-pyrolysis of wood and straw with up to 50 wt% basanite rock powder preserves the full pyrogenic carbon sink while embedding weatherable mineral surfaces directly into the biochar matrix. Vorrath et al. (2025) quantified both pyrogenic and inorganic carbon removal in a 27-week incubation on an Oxisol - the first combined PyC + IC sink measurement for co-pyrolysed materials, confirming that both CDR pathways operate simultaneously.

The real significance of PyMiCCS lies in its global potential. The method targets the 1.5 billion hectares of degraded tropical cropland and pasture where soil carbon has been depleted, mineral nutrients exhausted, and conventional restoration too expensive. On these soils, biochar and rock powder are not competing land uses - they are inputs that restore productive capacity while generating verified carbon removal. An outlook paper quantifying this potential on old, weathered tropical soils is in preparation.