Biogas is a mixture of methane, carbon dioxide and small quantities of other gases produced by anaerobic digestion of organic matter in an oxygen-free environment. This process is called

Anaerobic digestion of organic matter in an oxygen-free setting to yield methane-rich biogas is called bio-methanation.

Pelletization compresses waste into fuel pellets and is not a digestion process.

Pyrolysis decomposes matter by heat without oxygen but does not centre on microbial methane.

Leachate is the liquid draining through waste, not a process name.

In bio-methanation methanogenic bacteria convert organic acids into methane.

The residual slurry serves as a nutrient-rich manure.