Biogas from anaerobic digestion processes: Research updates

•Recent R&D works for biogas and anaerobic digestion process were reviewed.•Substrates, reactors, treatments, operation and system analysis were covered.•Research focuses and ways forward for AD process were discussed.

Anaerobic digestion (AD) is a biological process that can convert organic substrates to biogas in the absence of oxygen. The AD process has been practiced for centuries; however, it is still a research focus in contemporary literature. This mini-review selected papers published in 2015 and summarized the improvement and technological advancement and revealing current research and development trends for the biogas from AD process. A discussion on the challenges and prospects for developing improved AD technologies is provided.