Bio-CNG, also known as Compressed Biogas (CBG), is an upgraded version of the humble biogas, the dung-based version of which serves as cooking fuel in many villages in India.
The first stage of the CBG process is pre-treatment. The waste is passed through a trommel screen to remove hard materials like coconut shells and pieces of wood.
The screened waste is shredded in a hammer mill and made into a slurry with water. This slurry is kept in the pre-digester tank in aerobic conditions for one-two days to attract microbes — the process is called hydrolysis.
It is then transferred to an anaerobic digester where......