title: An index-based approach to assessing recalcitrance and soil carbon sequestration potential of engineered black carbons (biochars).
abstract: 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.
authors.affiliation: Texas Transportation Institute, Texas A&M University System, College Station, Texas 77843, United States. Omar.Harvey@pnnl.gov
authors.forename: Omar R
authors.initials: OR
authors.lastname: Harvey
authors.forename: Li-Jung
authors.initials: LJ
authors.lastname: Kuo
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Zimmerman
authors.forename: Patrick
authors.initials: P
authors.lastname: Louchouarn
authors.forename: James E
authors.initials: JE
authors.lastname: Amonette
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Herbert
mesh_terms: D002244:Carbon / Q000737:chemistry*; D057965:Carbon Sequestration; D002606:Charcoal / Q000737:chemistry* / Q000145:classification*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D008956:Models, Chemical; D018803:Models, Economic; D012987:Soil / Q000737:chemistry*; D013696:Temperature; D013818:Thermogravimetry
chemical_list: D012987:Soil; C540010:biochar; D002606:Charcoal; D002244:Carbon