Date of this Version
GCB Bioenergy. 2021;13:291–304.
Biochar is considered to sequester C and deliver other soil ecosystem services, but an overview that synthesizes the current knowledge of biochar implications on all essential soil ecosystem services is difficult to find in the ample biochar literature. Most previous research and review articles on this topic focused on a single ecosystem service and did not integrate all essential soil ecosystem services. This overview paper (1) synthesizes the impacts of biochar on water and wind erosion, C sequestration, soil water, nutrient leaching, soil fertility, crop yields, and other soil ecosystem services based on published literature and (2) highlights remaining research areas. Literature indicates that, in addition to se- questering C, biochar can reduce N2O emissions, nitrate leaching, and runoff; increase soil microbial biomass, plant available water, and crop yields (particularly in tropical regions), and CO2 emissions; and have small or no effects on water and wind erosion. Biochar bene- fits can be in this order: C sequestration > N2O emissions > Nitrate leaching > Available water > Soil biology > Soil fertility > Crop yields > Runoff. However, literature also indicates that biochar does not always improve all ecosystem services. Its benefits depend on biochar feedstock, pyrolysis temperature, application rate, biochar properties, soil properties, climate, and other factors. For example, biochar can enhance crop yields more in degraded and low fertility soils than in highly fertile and fine-textured soils. Long-term (>3 years) field-scale studies under different soil types, management conditions, and climates are needed for a determination of optimum levels of application, comprehensive life-cycle analysis, and assessment of agronomic and environmental tradeoffs. Overall, biochar can improve most soil ecosystem services, but the extent of such improvement is highly dependent on biochar properties and soil and climatic conditions.