Parametric and optimization studies for biochar production from municipal solid wastes (MSW) via pyrolysis

Abstract

The accumulation of municipal solid wastes (MSW) and the negative implications of using fossil fuels are some of the current environmental issues in the Philippines. Hence, this study aimed to utilize MSW by converting it into biochar through pyrolysis and maximize biochar production for energy application. The effects of pyrolysis parameters such as temperature and holding time on biochar yield were initially determined using 2k factorial experiment. Results showed that both factors had negative effects on biochar yield wherein temperature had a relatively higher impact. For the optimization study, Response Surface Methodology (RSM) was performed to determine the optimum pyrolysis conditions for maximum biochar production. The optimum conditions were found to be 300°C and 20 min holding time resulting to maximum biochar yield of 69.64 % by wt. Biochar characteristics were evaluated in terms of higher heating value (HHV), proximate and elemental analyses to determine its suitability as alternative fuel. The HHV of biochar obtained at optimum conditions was about 15.82 MJ/kg which is higher compared to that of the raw MSW (14.42 MJ/kg) and biochar obtained at extreme conditions (13.03 MJ/kg). Moreover, the energy recovery at optimum conditions based on biochar yield was about 76.37% which was also higher compared to that of the biochar obtained at higher temperature and holding time which was about 32.75 %. Using van Krevelen diagram, MSW-derived biochar at the optimum conditions can be classified as lignite, while MSW-derived biochar at extreme conditions is comparable to anthracite coal.