What is a good testable question for energy from garbage. How to make biogas?

For starters, energy is not a physical unit. It is a philosophical concept and an accounting technique used to analyze mechanical and chemical exchanges. In nuclear physics it is defined as a wavelength of light, in biology it is a synonym for metabolism, and in public utilities they say energy when they mean connectivity. Anybody who uses the word in any other context either does not know what he is talking about, or is peddling something you don't need.

"Biogas" can mean a lot of things. You have to explain exactly what you are talking about.

Power from garbage depends on what you mean by 'garbage'. It's not a big deal to generate methane from a sewer, but it takes a lot of animal poop to balance all the leaves and grass clippings. To produce more gas than a stove uses takes a small ranch. Here is a book that you need to find: www.amazon.com/s?ie=UTF8&field-keywords=other%20homes%20and%20garbage