A study of chemical pre-treatment and pyrolysis operating conditions to enhance biochar production from rice straw

Biochar utilization has been studied widely for applications in soil amendment and as an energy carrier. When optimizing biochar production, using rice straw (RS) as the source, few chemical pre-treatments have been investigated, but knowledge to date is still limited on how to enhance the properties of the biochar for its utilization in the energy sector. In this study, pyrolysis experiments were conducted using two chemical additive solutions containing: ammonium sulphate (AS) and diammonium phosphate (DAP) for RS pre-treatment; at different concentrations [0.1, 0.2 and 0.5 mol l-1], dwell times [30 and 60 min], and pyrolysis temperatures [300, 400, 500, and 600°C]. Pre-treatment of RS resulted in mass loss at lower temperatures, decreased rate of decomposition and increased char yields compared with untreated RS. The optimized pyrolysis conditions were 400°C, 30min dwell time, and 0.2 mol l-1 DAP pre-treatment, with 52.2% biochar yield. These conditions increased the biochar heating value and decreased the ash content to 19.27MJ/kg and 35.19%, respectively.