In rural china their farms traditionally have one, like a tank they route sewage and scraps and whatever, and they pipe off the gasses for cooking and heating and such, as it produces methane and the like.

you can use an anaerobic digestion system to generate about 100 liters of gas a day, given that you feed it around a liter of 50/50 food scraps and water slurry. you can heat a stirling engine with it to generate 2-300W or so.

it’s not risk free of course, biogas is explosive, but taking precautions can minimize it. produce and store outside, under low pressure, limit the volume, and use filters and flame arrestors.

this video is a good intro to the subject.

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another interesting avenue if you have access to cheap wood is syngas. you can run clean syngas in a unmodified internal combustion engine, so the generator part is easy. clean gasification is the hard part, since you need to get rid of the tar and water content. using charcoal is the best method because all that gunk is already burned off. you put it in an airtight container with an inlet and an outlet, light it at the inlet, and pump in a controlled amount of air. the charcoal then goes through a redox reaction and produces syngas at the outlet.

a syngas generator can produce roughly 10x the energy of a biogas plant of the same size, but involves high temperatures and more preprocessing.

here’s a video on that too.

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lastly, what’s more important to you? lowering your bills or being energy independent? my housing co-op has a deal with a local electricity company where they installed a load-following battery bank in our basement. it tracks the energy market so it can charge at night, be used by us during the day, and sell the surplus to the grid. it has lowered our energy bills by about a third. a lot less messy than the other two solutions, but also a lot less independent. doesn’t really matter for our situation, since we’re on district heating as well, but your situation may be different.