Improving biogas production using additives in anaerobic digestion: A review

Anaerobic digestion (AD) is one of the most popular renewable energy technologies. The AD process produces sustainable energy using various low-cost wastes. Although AD technology is widely used, its low biodegradation efficiency and poor stability limit its commercial application. The use of additives has been shown to offer marked improvements in AD performance. However, in practice, the use of additives in AD is not fully understood. In this review, the principles and achievements of additives (including metal elements, carbon-based accelerants, biological additives, and alkali addition) promoting AD performance are summarized. The review also discusses the issues and development trend of each additive. There are still many challenges associated with using additives in AD systems owing to significant variations in digestion substrates and AD operational procedures. The dosage and types of additives have a great influence on the efficiency of AD, which mainly depend on the substrate. Moreover, the implementation process of each additive is not perfect. Therefore, it is essential to better utilize additives to promote AD performance according to the merits of each material. The application of composite additives requires further exploration to optimize the implementation process. This paper deepens our understanding of flexible additives in the AD process and provides comprehensive information that can be used to promote renewable clean energy. (C) 2021 Elsevier Ltd. All rights reserved.