Small Scale Testing For Biogas

After sleeping on this, I think it might work. However, there are few things I'm worried about:

1.) Production rate & required inputs to make that happen
2.) Smell
3.) Methane capture from the compost pile
4.) Making a generator run for a sustained period

I think this is all going to take tinkering to make it happen. So, it should be done on a small scale basis using cheap stuff like 5 gallon buckets, plastic trash cans, and model airplane engines. If it can be made to work that way, it should work at larger scale, better. These things get more efficient with size.

I did have an experience with the composting. When I was in jr. high I decided to try to raise worms. It was my first attempt at producing something I could sell. Failed. I put garden soil and mulch in a couple of trash cans. I drilled a bunch of little holes all over the trash cans to let in air. Logical to me at the time. They sat in the basement. After a few days they got hot. Had to be over 120. That killed the worms. Out of paper route money and not having a clue what happened I gave up. Now I can see I had set up the perfect composter. For worms I needed less organic material and more dirt. For composting it was great. That probably helped heat the basement all winter that year. It was an old drafty basement so who knows how much methane there was.

There was no hydrogen sulfide as there was no rotten egg smell. I'm sure adding in some sulfur would have done the trick there!

So .. a 30 gallon Rubbermaid trash can and some clippings from the yard should work for that just fine.

As I said I think the waste digester will be fine with 5 gallon buckets and such.

Thinking about this, the pressures could be high. Beer brewers and root beer brewers routinely have bottles explode. We are dealing with similar processes.

As for capturing the methane from the composter, I need to research the bio process. I needs air. Air is about 70 / 30 nitrogen / oxygen (plus a lot of other gasses). The carbon and the hydrogen have to be coming from the organic matter and the water. The nitrogen is from the organic matter and the air. The research I've done so far tells me that we get mostly methane and carbon dioxide from the pile. So, if we can meter the air that is introduced, we should be able to control the dilution of the methane with air.

My initial thoughts now are that the methane and carbon dioxide can be separated in a column under low pressure. They have different molecular weights so they should separate. I think. Both are heavier than air. We also might be able to find some membrane materials that will allow us to make a separation system.

Later,
John