Ideas for home-made biogas plant

[mukunthko]

I've been thinking of building a biogas plant that digests kitchen waste and produces bio-gas for a while now. I only want it to to work as a prototype, maybe connect a bunsen burner to it.

I've more recently been thinking of using an old pressure cooker. The bottom can be turned out on a lathe and a longer tube of the same size can be welded on to it. The tube can have threads cut on it with a threaded flange as well to empty out the waste and compress the gases inside the digestor.

The opening for the steam can be used to extract the gas from the digestor.

Just wondering if anyone has any opinions or suggestions about this idea, have already tried it ot have a better idea for me please.

Thanks

Mukunth

[thefinis]

It takes a lot of mass to produce gas. I think that your project will be too small to make any appreciable amount of gas. If you can store the output of a week or two then it might run that burner for a little while. I could be wrong and household waste might be rich enough but manure and urine usually make more burnable gas than hay or veg matter.

Biomass varies in % conversion to gas and even varies on the mix of gases it produces. Most of what you add to the digester passes through as compost/fert and your slurry from beginning to end is mostly water. It just means that it takes a lot of mass to produce gas. Think more like 30 gal trashcan size for a prototype.

Just my thoughts

Finis

[phil b]

I have to agree with Finis. I too tried this idea several years ago. It was a total flop. If you had a pig farm, you might come out ahead. I also knew a man that owned a dairy farm that tried on a large scale. He never made ends meet.

In the 1980's, there was a book called "A Chinese Biogas Manual" that Mother Earth News sold. It went into detail about how to produce methane for heat as well as cooking. You might see if that's still available.

You can load a heavy black trash can liner with water and organic material. A small amount of methane and some very good, high nitrogen compost can be made in a week or less if you put it in the hot sun. BTW, nitrogen gas will form first, so vent that.

Keep experimenting though. It's fun and you can learn moocho.

Hope this helps.

Phil

[Bruce S]

Mukunth;

   If that pressure cooker is a 20 quart size then as a starter or test one you should be okay with it.

Couple things that you'll need to help make it work with kitchen scraps.

For a test unit, you won't need the weight on the cooker, the mash itself will be heavy enough, instead get a screw in nipple fitting and a ploy type roll of tubing and run this to a smaller container so that the gas can bubble though it, this will take the deadly sulfur out of the gas as well and oxy out so the gas isn't explosive.

On another website (journey to forever) there has been tons of different studies done and there's even one by the person who is considered the father of modern day methods. Have a good look and then give it a try. One place you can help your's to work would be to find a person who has cats, Cats' urine contains ammonia and this is a jump starter for producing methane gas. It can be collected using news paper and the news paper shredded to help it brake down as well. When you start with the test unit, try and shred the scraps or mash them up before putting it in, this will help the stuff get going.

Do take a look over at the other site and enjoy the reading.

Most of the units built and not working is due to not following smoe simple guide lines.

Our daughter built one as a school science project using one of those 20 quart glass bottles and it worked once she got the correct method and mixture right.

Don't be in a hurry, it'll take about 2 weeks for it to start really going.

Hope this helps;

Bruce S

 

[gale]

There is actually a series of posts about this from a year ago.  My arguement had to do with the small amount of gas it will produce, but a fellow from India, had plans that used the waste of a single family to make cooking gas.  http://www.fieldlines.com/story/2006/4/26/133058/568

The problem with your design is that you have no way of eliminating outside air when filling the unit.  The big biogestors are generally a plastic bag.  You shove a slurry mix in one end and out comes digest material out the other and gas is siphoned out from under the central cover.  Having too much air will cause the gas to be unusable,you will produce co2 instead of methane.  The one system I am familiar, they actually burps the unit everytime it is filled.  They suck off all gas from the previous fill, open the ends, shove a pile of cow manure in (slurry), take a pile of digest material out.  reseal,  siphon all air out then wait until the bag refills.  We are also talking about a semi-load of manure being loaded in everyday.  Then they burn the gas in a catipillar generator set.  At the size you have you might be able to heat your lunch.  You are going to need a diaphram to keep the air off your bio load.

[GaryGary]

Hi,

There is a "Methane Generator Calculator" listed here:

http://www.builditsolar.com/Projects/BioFuel/biofuels.htm#Methane

One of the inputs is allows is lbs of Garbage, so it might give you some kind of estimate of what you should get out of your generator?

There are also plans for some small methane generators at the same link.

Gary