Soil carbon sequestration and biochar as negative emission technologies

• Published in: Global change biology Vol. 22; no. 3; pp. 1315 - 1324
• Main Author: Smith, Pete
• Format: Journal Article
• Language: English
• Published: England Blackwell Science 01.03.2016; Blackwell Publishing Ltd
• Subjects: afforestation; air; Air Pollutants - analysis; Albedo; biochar; bioenergy; Biomass; carbon; Carbon Sequestration; Charcoal; Charcoal - chemistry; Climate; Climate Change; Deforestation; Emissions; energy; energy costs; energy requirements; Environmental Monitoring; Greenhouse Effect; greenhouse gas emissions; Greenhouse gases; Land use; negative emission technology; Nutrients; sequestration; soil; Soil - chemistry; Soils; Water use; weathering; negative emission technology; soil; biochar; carbon; sequestration
• ISSN: 1354-1013; 1365-2486; 1365-2486
• DOI: 10.1111/gcb.13178

Despite 20 years of effort to curb emissions, greenhouse gas (GHG) emissions grew faster during the 2000s than in the 1990s, which presents a major challenge for meeting the international goal of limiting warming to <2 °C relative to the preindustrial era. Most recent scenarios from integrated assessment models require large‐scale deployment of negative emissions technologies (NETs) to reach the 2 °C target. A recent analysis of NETs, including direct air capture, enhanced weathering, bioenergy with carbon capture and storage and afforestation/deforestation, showed that all NETs have significant limits to implementation, including economic cost, energy requirements, land use, and water use. In this paper, I assess the potential for negative emissions from soil carbon sequestration and biochar addition to land, and also the potential global impacts on land use, water, nutrients, albedo, energy and cost. Results indicate that soil carbon sequestration and biochar have useful negative emission potential (each 0.7 GtCeq. yr⁻¹) and that they potentially have lower impact on land, water use, nutrients, albedo, energy requirement and cost, so have fewer disadvantages than many NETs. Limitations of soil carbon sequestration as a NET centre around issues of sink saturation and reversibility. Biochar could be implemented in combination with bioenergy with carbon capture and storage. Current integrated assessment models do not represent soil carbon sequestration or biochar. Given the negative emission potential of SCS and biochar and their potential advantages compared to other NETs, efforts should be made to include these options within IAMs, so that their potential can be explored further in comparison with other NETs for climate stabilization.