Anaerobic digestion of food waste for bio-energy production in China and Southeast Asia: A review

Rapid economic growth in Asia and especially in China, will lead to a huge increase of food waste (FW) production that is expected to increase by 278–416 million tonnes. Among various waste management practices, anaerobic digestion (AD) is a useful method to transform food waste, producing renewable energy/biofuel and bio-fertilizers. This review aims to investigate some of the key factors in proposing FW for anaerobic digestion, with particular reference to China and South East Asian countries. Food waste shows variable chemical composition and a high content of biodegradable material (carbohydrates, protein and lipid). This composition led to consistent biogas production that was reported, as average for Chinese FW, of 480 ± 88 LCH4 kg−1 VS (n = 42). Since these data are higher than those reported for energy crops (246 ± 36 LCH4 kg−1 VS), this makes FW a good candidate to substitute for energy crops, avoiding food-energy conflicts. FW co-digestion with different substrates improved total bio-methane production (on average), from 268 ± 199 mL g−1 VS to 406 ± 137 mL g−1 VS. Food waste pretreatment, also, seems to be very useful in increasing total biogas production. Physical and thermal treatments were the best, increasing biogas production by 40% and 30%, respectively. Techno-economic evaluation seems to indicate the feasibility of substituting EC with FW for producing biogas and reducing total biomass costs. To achieve this, separate collection sources need to be put into place, assuring high FW quality to promote a Circular Economy approach in FW management.