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Are you looking for an additional source of energy for your off grid retreat? While solar and wind have become popular among preppers, they both suffer from the same problem as most renewable sources of electricity. They’re both highly dependent on the weather, require large expensive batteries, and oftentimes the amount of energy they produce isn’t sufficient for your heating needs. Unless you can afford to cover your whole roof with solar panels (or cut back on your energy usage) you may have to rely on the grid for certain times of the year.
To cover that gap, you should try diversifying your power generation. One of the most overlooked, is the methane digester. This contraption can break down your human and food waste, while producing a daily supply of methane for your heating needs. It works by sealing off the waste from the outside air, and letting the bacteria consume the material. Normally the bacteria would utilize oxygen  during the decomposition process much like a compost pile. If the container is sealed however, eventually all of the oxygen is used up, and the bacteria dies off. They are then replaced with anaerobic bacteria that pick up where the previous organisms left off.
This anaerobic bacteria produces methane rather than carbon dioxide. With a properly built system, you can capture this gas and utilize it for your cooking and heating; or if you have the right equipment you can run a generator. In addition, once the waste has been completely broken down, it can be used as fertilizer.
So how do you go about building one of these systems? There’s actually several different methods that vary in cost and effectiveness. Fortunately many of them are simple enough to be built at home. After searching youtube for instructional videos, I found one that appears to show the cheapest and simplest design for a methane digester.
The only thing I would change is the grey plastic container to hold the waste. I don’t think that kind of box is capable of creating a proper seal. I would have used a bucket or drum of some kind, or added epoxy to the lid for a better seal.
Nevertheless, the video gives a pretty thorough description of how these systems are made, and any part of that digester could be replaced with something else. There are numerous videos and diagrams out there that can show you how to make a methane digester, and no two are the exactly the same. You’ll find a lot of variants on the design, and many alternative materials to use.
Overall, it’s a pretty cool system that anyone could build, no matter what kind of budget or materials you have at your disposal. It’s scalable, leaves no waste, creates fuel, and re-fertilizes the soil. If you’re looking for self sufficiency, I can’t think of anything that would be more helpful.