Methane generation

[urbanprep]

So I know from other posts that folks have gas, diesel, propane stored. Most folks seem to know the basics about or have experimented with wood gas. Has anyone tapped into the "septic tank" to try and get some methane generation going?

Obviously it is more than the septic tank.
Has anyone looked at or worked with developing a methane system? How much methane might be "lost" out of the vent stack of my home septic?


Any thoughts?

[woodyz]

We did a project in college where we converted an entire dairy farm to run on the methane produced by his cows.

We built two holding tanks like an above ground swimming pool with one end open and a big rubber bladder over it. One cooking while one was producing. The system used a front end loader on a tractor and placed barrier boards like dam slates to raise or lower as required. Spaced out to a days waste. Each tank held 30 days of poop. As it cooked the rubber bladder contained the methane and it was piped off like propane to power a generator for all of his electric needs. The poop came out dry and odor free and he sold about 1/2 of what was created.

One thing that amazed me was the amount of waste water created for about 40 cows and what to do with it. Before our project the farmer just diverted the water and poop waste back to his pastures. Good fertilizer for his grass, but terrible smell and real ground water issues.

Our project didn't include what to do with the waste water, but the way everything worked out we added it into the project. We used a slight sloop to stagger three holding tanks so each ones low point was on the same level as the next ones high point.

Once the upper tank settled for a few days the water was allowed to drain to the next tank so by the time it settled in the last tank he was able to reuse it, saving about half on the water he had been using and with a lot less smell. We still had a ground water issue so we used bladders on the bottom of these tanks and once the top tank was empty a few days he would drag the bladder out with the almost dry poop into the fields again but with a lot less runoff and a lot less smell.

All n all it was an interesting project. I would have liked to have used the sludge in the bottom of the water settling tanks in the methane tanks, but we ran out of time.

Now to the real question that was asked. From my experience I do not believe the methane created by a single family septic system would be worth the trouble to collect and use it. Maybe a community septic system where a whole housing project feeds to a single collection system would work, but you might get enough methane to take one or two houses off the grid but that would be it.

I have seen where a single family dwelling was able to collect enough methane from their septic system to supplement their house hold heating in the coldest part of the winter, but not much more.

That is my knowledge on it. I am sure they have made some advances since my college days.

My Mother runs her heat and her cooking off of the waste gas from a single oil well. The collector is only about 10 gallons most of her storage is in the line from the well to the collector. What she doesn't use is still bled off so the well pressure stays equal. She has been doing that off that one well for better than 40 years.

You have to bleed the air and water out of the collector once a day and when its cold enough you end up with a liquid gas you can separate from the water. My brother runs a motorcycle off of it and sometimes he drinks it. But based on how fried his little bit of brain is, I don't think I would recommend it.