Mineral-enriched biochar delivers enhanced nutrient recovery and carbon dioxide removal

Biochar production via biomass pyrolysis with subsequent burial in soils provides a carbon dioxide removal technology that is ready for implementation, yet uptake requires acceleration; notably, through generation of cost reductions and co-benefits. Here we find that biomass enrichment (doping) with refined minerals, mineral by-products, or ground rocks reduces carbon loss during pyrolysis, lowering carbon dioxide removal costs by 17% to US$ 80–150 t−1 CO2, with 30% savings feasible at higher biomass costs. As a co-benefit, all three additives increase plant-available nutrient levels. Doping with potassium-bearing minerals can increase both potassium and phosphorus release. Mineral doping in biochar production therefore offers carbon dioxide removal at lower costs, while alleviating global phosphorus and potassium shortages. This makes it unique among carbon dioxide removal technologies. Mineral doping of biomass prior to pyrolysis enhances carbon dioxide removal associated with biochar application to soils due to increased stable carbon yield, while also improving biochar fertiliser value through added nutrients and enhanced phosphorus availability.