Anaerobic digestion (AD) has the advantages of utilizing complex substrates and producing renewable energy and is currently one of the mainstream technologies for food waste (FW) resourcing. However, at high organic loads and low inoculum-to-substrate ratios (ISRs), AD with FW as substrate is prone to acid accumulation, resulting in a drastic decrease in gas production and system collapse. This study investigated the effect of the coupled addition of zero-valent iron (ZVI) and activated carbon (AC) on the AD of FW at three low ISRs of 0.715, 0.625, and 0.5. The results showed that the control group acidified and stopped producing biogas when the ISR decreased to 0.625 and 0.5, but ZVI coupled with AC alleviated the acidification and increased the cumulative biogas yield. Especially at ISR = 0.5, the cumulative biogas yield for the ZVI + AC group was 31.5%, 99.5%, and 11.43 times higher than that of the ZVI, AC, and control groups, respectively. ZVI coupled with AC also increased the degradation of volatile fatty acids (70.5–84.4%) and soluble chemical oxygen demand (50.0–72.9%) while decreasing propionate concentration and improving the stability of the AD system. COD mass balance analyses indicated that the coupled addition of ZVI and AC promoted the conversion of particulate organic matter to soluble organic matter and increased the conversion of carbon sources to methane.

The bibliometric method was used in this study to analyze current advances in the anaerobic digestion (AD) of cellulose waste. The result shows that the number of articles increased rapidly after 2010, suggesting a growing interest in this field. The USA and China were the top two countries with the highest number of published articles. AD of cellulose waste is being actively explored in many countries, and partnerships between countries are being actively formed. The top three subject categories were Environmental Sciences & Ecology, Engineering, Energy & Fuels. The most widely published and influential journals were Bioresource Technology, Water Science and Technology, and Waste Management. The co-occurrence and trend analysis of author keywords indicates that current research is primarily focused on pretreatment and co-digestion. Microbial community analysis plays a crucial role in elucidating the mechanisms, and life cycle analysis (LCA) could evaluate the impact on the environment at different stages. Microbial community analysis and LCA will be the hotspots in the future. To some extent, this study helps to understand the current global status and trends of the related research.