Improving Carbon Sequestration Capacity of Biochar By Pre-Treating Biomass.

Biochar production and its soil application have been proposed as a potential strategy for carbon sequestration. Biochar is produced by pyrolysis, a carbonization process, in which approximately 50% of the biomass carbon generally remains in the biochar. In this study, we examined pre-treating biomass in order to convert more biomass carbon to biochar and thereby improve the carbon sequestration capacity. Prior to pyrolysis, several P-containing substances were added to biomass to test their ability to increase biomass carbon retention in the designed biochars. We found that using TSP chemical fertilizer as an additive could significantly increase the carbon retention during biomass pyrolysis. Compared to unmodified biochar with 50% carbon content, up to 75% biomass carbon could be contained in the designed biochars produced from switchgrass mixed with TSP. Thermo-gravimetric analysis showed that the oxidative stability of the designed biochar was significantly enhanced, suggesting that it is recalcitrant to chemical degradation. A soil incubation experiment was conducted to determine biochar microbial stability in soil. The results showed that the designed biochars were very stable in soils and that the TSP additive did not influence their microbial decomposition. Applications for this designed biochar will be discussed.