Microaerobic condition as pretreatment for improving anaerobic digestion: A review

[Display omitted] •The effect of microaerobic pretreatment (MAP) on anaerobic digestion was reviewed.•MAP improves methane production by between 30% and 216% by hydrolysis improvement.•A new mechanism for explaining microaerations impact on hydrolysis was proposed.•Financial analysis shows that MAP is interesting for industrial implementation.•Efforts on environmental and economic analysis and modelling of MAP must be done. Pretreatment of waste before anaerobic digestion (AD) has been extensively studied during the last decades. One of the biological pretreatments studied is the microaeration. This review examines this process, including parameters and applications to different substrates at the lab, pilot and industrial scales, to guide further improvement in large-scale applications. The underlying mechanisms of accelerating hydrolysis and its effects on microbial diversity and enzymatic production were reviewed. In addition, modelling of the process and energetic and financial analysis is presented, showing that microaerobic pretreatment is commercially attractive under certain conditions. Finally, challenges and future perspectives were also highlighted to promote the development of microaeration as a pretreatment before AD.