The effect of pyrolysis temperature on the characteristics of biochar, pyroligneous acids, and gas prepared from cotton stalk through a polygeneration process

Abstract

The biochar (BC), pyroligneous acid (PA), and gas were collected from cotton stalks based on a polygeneration process, and this study was systematically focused to develop and process biochar and its byproducts obtained with various pyrolysis temperatures (300, 350, 400, 450, 500, and 550 °C). The results showed that the yield of biochar decreased from 46.71 % to 30.26 % as the pyrolysis temperature was increased from 300 to 550 °C, and this was accompanied by an increase in carbon content from 71.32–78.02%. Heatmap analysis on the correlation among pyrolysis temperature of biochar and elements illustrated that the content of C, H, and O were highly correlated with pyrolysis temperature of biochar. The ketones, phenols, alcohols, acids, and alkyl phenyl ethers were the major chemical constituents. The maximum total content of amino acids reached 647.1 mg/kg when the pyroligneous acids were collected at 450 °C. Moreover, the volume fractions of gas (CO and CH4) content increased with increasing pyrolysis temperature, leading to an increase in the gas heating value. Overall, the outcomes presented above indicated that the polygeneration system would be environmentally benign and effective in producing biochar, pyroligneous acids, and gas, which provides economic benefits and suggests a potential industrial application for cotton stalk.