A miniature version of this is fairly cheap and simple to produce on any small Homestead. Coffee grounds produce about twice as much gas per pound as does cow manure. So even those in Suburbia, without animals can easily get plenty of feedstock using their grass clippings and waste that are gathered around the city.
This 2 cubic yard system produces about three hours of cooking gas per day.
The African boy in the second photo is making a gas delivery from his mother's gas plant. He gathers up manure from the donkeys and cattle that are herded through his village. This delivery weighs 9 pounds. The gas is lighter than air. When he picks up the empty bag, it weighs 12 lb. They use the nutrient-rich effluent liquid on their garden.