Food waste anaerobic digestion plants: Underestimated air pollutants and control strategy

Food waste management is an important global issue, and anaerobic digestion (AD) is a sustainable technology for treating food waste and developing a circular economy. Odor and health problems in AD plants have drawn increasing public attention. Therefore, this study investigated the odor characteristics and health risks in different workshops of food waste AD plants. At each site, the treatment capacities for kitchen and restaurant waste were 200 and 200-250 tons per day, respectively. Among the detected odorants, ethanol was the dominant component in terms of concentrations, while methanethiol, propanethiol, H₂S, and acetaldehyde were the major odor contributors in different workshops. The odor contribution of propanethiol had been previously overlooked in several workshops. The unloading, pretreatment, and bio-hydrolysis workshops were identified as major areas requiring odor control. Besides odor, carcinogenic and non-carcinogenic risks commonly existed in food waste AD plants. The carcinogenic risk of acetaldehyde had been underestimated previously, and it was identified as the dominant carcinogen. Furthermore, benzene was a potential carcinogen. Non-carcinogenic risks were mainly caused by acetaldehyde, H₂S, and ethyl acetate. The health risks were not always consistent with odor nuisance. Based on the odor and health risk assessments, several air pollution control strategies for food waste AD plants were proposed, including food waste source control, in-situ pollution control, and ex-situ pollution control.