Biogas generation from by-products of edible oil processing: a review of opportunities, challenges and strategies

Edible oil processing by-products can be used to produce a renewable fuel called biogas through anaerobic digestion technology. In this process, the physicochemical characteristics of the substrates dictate the process conditions, stability and microbial profile. All these, in turn, affect the overall digester design and operational efficiency. Most edible oil processing by-products tend to exhibit comparatively similar physicochemical properties, allowing for echo studies to be conducted on them. Naturally, residual fats and oils in edible oil by-products should induce high methane production potential. However, this does not occur without certain drawbacks. In this work, a review is conducted on biogas systems that use edible oil processing by-products as substrates for anaerobic digestion. Anaerobic digestion opportunities and challenges associated with these substrates are identified by analysis of factors that affect anaerobic digestion. The factors are scrutinised under different sub-headings, viz., substrate physicochemical composition, process conditions and parameters. Knowledge gaps are identified. Additionally, strategies for resolving some of the highlighted challenges while leveraging opportunities identified are discussed.