Carbon potentials of different biochars derived from municipal solid waste in a saline soil

Abstract

There are numerous studies conducted on biochar for its carbon (C) sequestration potential; however, there are limited studies available on the behavior of salt-affected soils related to biochar application. Therefore, more studies are needed to elucidate the mechanisms through which biochar affects saline soil properties. In this study, biochars were produced from solid waste at pyrolysis temperatures of 300, 500, and 700 °C (BC300, BC500, and BC700, respectively) and applied to a saline soil to evaluate their impacts on soil carbon dioxide (CO 2 ) efflux, C sequestration, and soil quality. A soil incubation experiment lasting for 107 d was conducted. The results showed that soil CO 2 efflux rate, cumulative CO 2 emission, active organic C (AOC), and organic matter (OM) significantly increased with BC300 application to a greater extent than those with BC500 and BC700 as compared to those in the no-biochar control (CK). However, soil C non-lability did not significantly increase in the treatments with biochars, except BC700, as compared to that in CK. Besides improving the soil quality by increasing the soil AOC and OM, BC300 showed positive impacts in terms of increasing CO 2 emission from the saline soil, while BC500 and BC700 showed greater potentials of sequestering C in the saline soil by increasing the soil non-labile C fraction. The recalcitrance index ( R 50 ) values of BC500 and BC700 were > 0.8, indicating their high stability in the saline soil. It could be concluded that biochars pyrolyzed at high temperatures (≥ 500 °C) could be suitable in terms of C sequestration, while biochars pyrolyzed at low temperatures (≤ 300 °C) could be suitable for improving saline soil quality.