Comparison of biogas production from anaerobic co-digestion of high-solids and liquid food waste and green waste by batch method: A case study of Imam Ali (AS) Military University

Anaerobic Digestion (AD) is an alternative process for the treatment of organic waste that enables the energy production in biogas. In addition, the total volume of waste transported to landfills decreases, thus increasing the lifespan of landfills. Considering the different sources of organic waste, food waste (FW) is of great importance because large quantities are produced and buried. For this purpose, co-digestion of FW and green waste (GW) with five mixing ratios of raw materials was performed to evaluate biogas production. Increasing the percentage of GW in the substrate led to increased methane yield. The highest biogas production was determined in the ratio of FW and GW 50:50. About 90% of methane yield was obtained after 21 days of digestion with a total yield of 425 ml/g VS. Based on the preferred ratio, the effect of total solids (TS) on co-digestion of FW and GW ranged from 5 to 25% TS. The results showed that the methane yield from digestion of high-solids AD (HS-AD) (15 to 20% TS) was higher than that of liquid AD (L-AD) (5-10% TS), while further increasing the TS content to 25%, disrupted the function of methanogenesis. This inhibition may be due to overloading of the organic charge and the formation of excess ammonia.