Towards “set-in-stone” co-deployment of enhanced rock weathering and biochar – an experimental study on their CO2 removal and agronomic co-benefits

To limit global temperature rise well below 2⁰C, Carbon Dioxide (CO2) Removal (CDR) strategies, such as Enhanced Rock Weathering (ERW) and biochar, are urgently required. Besides CDR, ERW releases nutrients and trace metals, while biochar surfaces may bind these weathering products. The main objective of this research was to experimentally study whether and through which processes ERW, and biochar co-deployment, can promote carbon sequestration, while limiting trace metal risks and providing agronomic co-benefits. A soil column experiment showed a high enhanced weathering potential for the mineral wollastonite, while the potential of olivine was limited by its nickel release. Two greenhouse pot experiments revealed that biochar co-deployment can reduce these trace metal risks. A two-year lysimeter field experiment showed that the increase in soil pH was the main agronomic co-benefit of ERW. While the potential CDR of ERW was substantial, the actual CDR observed was limited by soil retardation mechanisms.