Solar‐powered microwave pyrolysis of corn stover for value‐added products and process techno‐economic assessment

Abstract

SummaryMicrowave pyrolysis, powered by the solar photovoltaic (PV) electricity has been studied for safe and effective disposal of one of the abundantly available agro‐residues that is, corn stover (CS) in India. The study focuses on maximizing the yields of value‐added products that is, wood vinegar and biochar, because of their several applications in the agriculture and easy trading among the farmers with a scope of earning higher economic benefits. The effects of different levels microwave power, reaction time, and various concentrations of additive (biochar) on the yields of the pyrolytic products have been investigated. Under the optimal conditions of pyrolysis (input power of 700 W for microwave, pyrolysis reaction duration of 20 minutes and use of 5% additive from biochar), the yields of wood vinegar and biochar were measured to be 31 and 34 wt%, respectively, with the lower yields of both tars (9.64 wt%) and gas (25.2 wt%). The wood vinegar, obtained from the study, contained about 28%‐32% acids, 10%‐15% phenols, 18%‐20% ketones, and 12% alcohol with the pH in the range of 2.94‐3.21. The lower heating value (LHV) of biochar ranged from 22‐27 MJ/kg. From the techno‐economic and environmental assessment, the monthly income, payback period and quantity of CO2 mitigation are estimated to be USD 44, 3.5 years and 25.6 tones in case of lab‐scale set up and USD 44114, 1.7 years, and 20 549 tones for scaled‐up production systems, respectively. These findings would contribute to diminish the greenhouse gases emissions, mitigate climate change, and help to derive economic benefits for the farmers along with the effective utilization of agro‐residues.