2022/3/1/ · AD is a process that occurs in nature (e.g., in cow stomachs), but in a biogas plant it can be controlled and optimized to yield more methane (Al Seadi and Lukehurst, 2012).Biogas consists of methane (CH 4) (45–75%, V/V), as a renewable energy source, carbon dioxide (CO 2) (25–55%), and small amounts of hydrogen sulfide (H 2 S) and hydrogen (H 2)