43 / 2023-04-30 22:04:20

Anaerobic fermentation improved the property of biochar from food wastes: Focus on the effects of inoculum to substrate ratio and pyrolysis temperature

Food wastes,Biochar,Anaerobic pretreatment,ISR,Pyrolysis temperature

Food wastes (FW) generally contain carbohydrates, proteins, lipids, and other carbonaceous substances, which can be further converted to various value-added products (such as soluble carbon source via anaerobic fermentation and functional biochar via pyrolysis). In this study, anaerobic fermentation was carried out to pretreat FW before pyrolysis and the effects of inoculum to substrate ratio (ISR, 1:2, 1:1 and 2:1) and pyrolytic temperature (400, 600, 800 °C) on the properties of biochar were investigated. The results showed that anaerobic fermentation of FW not only achieved as high as 535.9±23.6 mg/g-VS production of short chain organic acids (SCOAs) at the ISR of 2:1, but also improved the property of biochar from FW, particularly the pore size and specific surface area (SSA). The pore size is not detected in the raw FW derived biochar, while the average pore size of biochar from FW pretreated by the anaerobic fermentation reaches to 4-6 nm, belonging to mesoporous materials. The SSA of biochar from raw FW is bolow 2.01 m²/g and FW fermented at ISR of 1:2 is only 13.67 to 61.33 m²/g at different temperature, while it is promoted enormously to 350.83 m²/g at 800 °C when the ISR increases to 1:1 and 313.10 at 600 °C when ISR at 2:1. The pyrolytic temperature also affected the SSA of biochar in spite of the FW was anaerobically pretreated. Biochar pyrolyzed at 400 °C can not obtain eminent SSA (maximal 62.88 m²/g) since insufficient carbonization while excessive temperature of 800 °C might lead to the collapse of the porous structures in biochar obtained at the highest ISR of 2:1 and the decreased SSA of 277.15 m²/g.