Over-acidification control strategies for enhanced biogas production from anaerobic digestion: A review

Over the years, anaerobic digestion (AD) technology has earned considerable attention because in addition to treating organic wastes, it can produce biogas as a viable substitute for conventional fossil fuels. However, the widespread application of AD is restricted by concerns about the reduced efficiency and profitability of the process due to a variety of inhibitors. The excessive acidification of AD processes due to the accumulation of volatile fatty acids (VFAs) is one of the most commonly encountered drawbacks in AD, which can lead to instability and, even in some cases, the failure of the entire process. Therefore, many efforts have been made so far to tackle this problem and maximise AD biogas output. The present work aims to provide a detailed overview of the main strategies undertaken for controlling over-acidification in AD as a useful source of knowledge for future research and further development of biogas technology worldwide.