A biodigester is a simple device: just a sealed chamber full of just about anything that was once alive (such as meat, vegetables, flour, leaves, or poop) and water. These ingredients are consumed by bacteria with a byproduct of methane gas (CH4).
Methane, of course, is combustible, and can be used for cooking, burned for light, or fed into an engine to produce electricity, pump water, or other useful purposes. The only hitch is the digestion process only works in an oxygen-free environment. And in case you haven't noticed, Earth has got oxygen, like, all over the place.
We were cleaning out the refrigerator, so I says to myself, self let's make some gas. The first thing to go in was a jar of pickle juice with a few bits of pickle afloat and seemingly unaware of their immanent sacrifice in the name of science. Then I put in some old raisins that were all stuck together, and some nuts. I chopped them all up in a blender first to liquefy the "feedstock" as much as possible. This is because bacteria don't have teeth.
Next to go were some stale hamburger buns, old baked potatoes, and a few hot dogs of questionable age.
Some muffin mix, cake mix, and cornbread mixes went in easily. A little baking soda helps reduce the acidity which makes the bacteria happy so that they smile little toothless smiles.
I poured in some crushed potato chips and old V8 juice that we bought out of nutritional guilt, a guilt that proved insufficient to actually make us drink it.
The blender made a good paste out of a bag of old peanuts.
Jono helped me with this project. He told me to take a picture of him pretending to eat it. All jocularity, that one.
The food scraps filled the barrel to about 5 gallons. I added equal parts of water for a total volume of 10 gallons. Ready to rot. The 40 gallons of air will not be a problem, as it will be consumed by the first stage of digestion. As long as no new oxygen source is available, we should be growing bacteria like no body's business.
Then I put on the air tight cap and lugged it out into the back yard. It would probably work better in the house because it is winter. The bacteria thrive best between 45-108 F, and lately it has been getting colder than that at night. But you really can't ask your wife to keep a thing like this in the house, no matter how tolerant she is.
More gas news as it passes...