Biodegradability and transformation of biodegradable disposables in high-solids anaerobic digestion followed by hydrothermal liquefaction

Despite the increasing use of biodegradable disposables, there is a shortage of information in the literature about their biodegradability in biological waste treatment processes like high-solids anaerobic digestion (HSAD). This study investigated the biodegradability and transformation of biodegradable disposables in an integrated process of HSAD followed by hydrothermal liquefaction (HTL). The paper-based disposables were efficiently degraded in HSAD. Conversely, compostable plastic bags and utensils did not degrade and resulted in a decrease of 29.5% and 8.99%, respectively, in methane yield compared to the control. However, HTL could completely transform undegraded plastic bags and utensils in the HSAD digestate into biocrude, thereby decreasing the potential environmental risk of bioplastic pollution from the land application of digestate. Moreover, increasing HTL temperature from 280 to 350 °C could enhance the yield and quality of biocrude in terms of heavy oil content. These results provide new insights into sustainable management and valorization of biodegradable disposables.