Chapter 8. Soil Carbon Sequestration and Biochar

The greenhouse gas removal (GGR) potential of soil carbon sequestration (SCS) and biochar is achieved via a deliberate increase in the soil organic carbon (SOC) stocks. This can be realised by improving management practices in agriculture and grassland systems by increasing the organic carbon (C) input or reducing soil disturbances. Soil C sequestration potential differs depending on climate, soil properties and management, with the highest potential for poor soils (SOC stock farthest from saturation). The main downside of using SCS for CO2 removal is the limited time C can be sequestrated until a new C equilibrium is reached. SCS management needs to continue even after C saturation in the soil occurs, otherwise, the newly gained SOC stock might lose the C again, reversing the SCS impact. However, agricultural and grassland soils have the feasible technical potential of 2–5 Gt CO2eq per year globally and an economic potential of 1.5–2.6 Gt CO2eq per year (at prices up to 100 $ per t CO2eq). They can act as a C sink over the next 20 to 30 years following SCS management implementation. Biochar is more recalcitrant, and a new C equilibrium is expected to take much longer, so, biochar will probably be a long-term option for CO2 removal. Biochar's feasible technical potential is 2.6 Gt CO2eq per year. Both SCS and biochar can be implemented on existing land and bring additional benefits for soil quality and health, which provides further advantages like an increase in productivity. Thus, SCS and biochar can contribute greatly to sustainable productivity and food security.