Experimental evidence for sequestering C with biochar by avoidance of CO 2 emissions from original feedstock and protection of native soil organic matter

• Published in: Global change biology. Bioenergy Vol. 7; no. 3; pp. 512 - 526
• Main Authors: Herath, H. M. S. K., Camps‐Arbestain, M., Hedley, M.J., Kirschbaum, M.U.F., Wang, T., van Hale, R.
• Format: Journal Article
• Language: English
• Published: 01.05.2015
• ISSN: 1757-1693; 1757-1707
• DOI: 10.1111/gcbb.12183

Abstract There is a need for further studies to compare the decomposition of biochar to that of the original feedstock and determine how these amendments affect the cycling of native organic matter ( NOM ) of different soils to improve our understanding of the resulting net C sequestration potential. A 510‐days incubation experiment was conducted (i) to investigate the evolution of CO 2 from soils amended with either fresh corn stover ( CS ) or with biochars produced from fresh CS at either 350 ( CS ‐350) or 550 °C ( CS ‐550), and (ii) to evaluate the priming effect of these amendments on NOM decomposition. Two soil types were studied: an Alfisol and an Andisol, with organic C contents of 4% and 10%, respectively. Except for the controls (with no C addition), all treatments received 7.18 t C ha −1 . We measured C efflux in short‐term intervals and its isotopic signature to distinguish between C evolved from C 4 amendments and C 3 ‐dominated NOM . Emission rates were then integrated for the whole time period to cover total emissions. Total CO 2 ‐C evolved from the original C in fresh CS , CS ‐350 and CS ‐550 was greater in the Andisol (78%, 13% and 14%) than in the Alfisol (66%, 8% and 7%). For both soils, (i) no significant differences ( P  >   0.05) were observed in the rate of CO 2 evolution between controls and biochar treatments; and (ii) total accumulated CO 2 evolved from the uncharred amendment was significantly higher ( P  <   0.05) than that from the other treatments. In the Alfisol, a significant ( P  <   0.05) net positive priming effect on NOM decomposition was observed when amended with fresh CS , while the opposite was detected in biochar treatments. In the Andisol, no significant ( P  >   0.05) net priming effect was observed. A C balance indicated that the C lost from both biochar production and decomposition ‘broke even’ with that lost from fresh residue decomposition after <35 weeks. The ‘break‐even’ point was reached earlier in the Andisol, in which the fresh CS mineralizes faster. These results provided experimental evidence for the potential of biochar to sequester C and avoid CO 2 emissions from original feedstock while protecting native soil organic matter.