Biochar and pyrolysis liquid production from durian peel by using slow pyrolysis process: Regression analysis, characterization, and economic assessment

Abstract

This study examines the conversion of durian peel to biochar and pyrolysis liquid via slow pyrolysis. The central composite design was utilized to optimize the conditions of three independent variables, namely pyrolysis temperature, cooling temperature, and holding time. Analysis of variance revealed that only pyrolysis temperature had a significant effect on biochar and pyrolysis liquid yields. The biochar and pyrolysis liquid yields fit by a second-order polynomial model agreed well with experimental results. As the pyrolysis temperature increased, the solid product yield decreased, while the pyrolysis liquid yield increased. The highest biochar and pyrolysis liquid yields were 56.11% and 38.53% that derive at 300 and 600 °C of pyrolysis temperature, respectively. The validation of both prediction models showed over 96% agreement. Biochar of high heating value (26.55 MJ/kg) was obtained at 600 °C pyrolysis temperature and 30 min holding time. According to the Van Krevelen plot, the molar ratios of the H/C and O/C of the biochar obtained at 600 °C of pyrolysis temperatures were similar to coal material. The high-quality biochar was of carbon storage class 4 according to the IBI classification; and the characteristics of pyrolysis liquid met community product standards of Thailand. An economic analysis was performed to assess the feasibility of converting 60 tons/year of durian peel into biochar and pyrolysis liquid. An internal project rate of return (IRR) of 25.91% with a payback period of 1.58 years was estimated. The findings of this study indicate the economic viability of immediately deploying large-scale pyrolysis utilizing a waste stream from agriculture.