An Index-Based Approach to Assessing Recalcitrance and Soil Carbon Sequestration Potential of Engineered Black Carbons (Biochars)

• Published in: Environmental science & technology Vol. 46; no. 3; pp. 1415 - 1421
• Main Authors: Harvey, Omar R, Kuo, Li-Jung, Zimmerman, Andrew R, Louchouarn, Patrick, Amonette, James E, Herbert, Bruce E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 07.02.2012
• Subjects: 09 BIOMASS FUELS; biochar; Biodegradation; BIOMASS; Carbon - chemistry; CARBON SEQUESTRATION; Charcoal - chemistry; Charcoal - classification; Chemical compounds; Climatology. Bioclimatology. Climate change; Earth, ocean, space; econometric models; ECONOMICS; Environmental Restoration and Remediation - methods; Exact sciences and technology; External geophysics; graphene; GRAPHITE; Meteorology; MINERALIZATION; Models, Chemical; Models, Economic; Physical properties; physicochemical properties; phytomass; screening; Soil - chemistry; SOILS; soot; STABILITY; Temperature; Thermogravimetry; Combustion residue; Carbonaceous materials; heat treatment; Biochar; Carbon sequestration; Thermal stability; greenhouse gas; sustainable development; Mitigation; mineralization; Economic model; charcoal; climate change; Thermal degradation
• ISSN: 0013-936X; 1520-5851; 1520-5851
• DOI: 10.1021/es2040398

The ability of engineered black carbons (or biochars) to resist abiotic and, or biotic degradation (herein referred to as recalcitrance) is crucial to their successful deployment as a soil carbon sequestration strategy. A new recalcitrance index, the R 50, for assessing biochar quality for carbon sequestration is proposed. The R 50 is based on the relative thermal stability of a given biochar to that of graphite and was developed and evaluated with a variety of biochars (n = 59), and soot-like black carbons. Comparison of R 50, with biochar physicochemical properties and biochar-C mineralization revealed the existence of a quantifiable relationship between R 50 and biochar recalcitrance. As presented here, the R 50 is immediately applicable to pre-land application screening of biochars into Class A (R 50 ≥ 0.70), Class B (0.50 ≤ R 50 < 0.70) or Class C (R 50 < 0.50) recalcitrance/carbon sequestration classes. Class A and Class C biochars would have carbon sequestration potential comparable to soot/graphite and uncharred plant biomass, respectively, whereas Class B biochars would have intermediate carbon sequestration potential. We believe that the coupling of the R 50 , to an index-based degradation, and an economic model could provide a suitable framework in which to comprehensively assess soil carbon sequestration in biochars.