Characteristics and Potential Values of Bio-Products Derived from Switchgrass Grown in a Saline Soil Using a Fixed-Bed Slow Pyrolysis System

Abstract

Switchgrass harvested from saline soil was slowly pyrolyzed at 300, 500, and 700 °C in a fixed-bed reactor. The objective was to understand the characteristics and evaluate the potential values of the bio-oil, syngas, and biochar. The biochar yield (27.0% to 41.3%) decreased with increasing temperature, whereas the syngas yield (26.3% to 40.9%) increased. The bio-oil yield (30.8% to 34.1%) was highest when the switchgrass was pyrolyzed at 500 °C. Both the bio-oil and syngas had low value as direct fuels because of their low heating values. Compared with the biochars from the switchgrass grown in “sweet” soil, the biochars derived from the switchgrass grown in saline soil had higher values of ash (10.5% to 17.2%), mineral nutrients, and cation exchange capacity (CEC) (200.3 to 241.1 cmol/kg). These results suggested that the biochar generated in this study might have a better liming effect and improvement of soil fertility and crop growth as a soil conditioner, and lead to double wins in saline soil improvement and a new approach for switchgrass utilization.