Either this topic is misleading OR you didn't answer the person's question correctly, Biogas is the gas extracted from a biodigester(the container holding organic waste for gas production), it consists of a mixture of gases which are methane (the desired gas), carbondioxide(unwanted gas) and hydrogen sulphide (unwanted gas). A biodigester is air-tight container, compartment or enclosure that holds the organic waste for anaerobic digestion that will bring the production of gas, it can be constructed using different types of containers ranging from PVC gallons, Jerrycans and water storage tanks or constructed like sausage or barrel shape below the ground with cement and concrete(plug flow type).
Thanks for enlightening us. As I watched this video, I wonder if this system could be generated for domestic cooking in our kitchens. Do you have any plans for such?