Just a little background, my BS is in Energy Science. However, methane generation is always a subject that has peaked my interest. Now that we are going to have 6 hayburners here in the fall, I think it is time to start exploring the potential of electricity generation from the piles of manure that are generated. The theory is to fire a small generator and sell back the power into the grid, and perhaps time its use with high demand periods here such as when the central A/C is on. The byproduct of composted manure is also going to reduce my current cycle time of composting.
I've not even began the research; it seems the containment and moveing the material in and out is the hardest part of the venture. I was conceptualizing an "in at the top out at the bottom" type of vessel for containment. I'm also looking for some farms that may be up and running with methane generation now to visit, there are some here in the Northeast.
Any thoughts or experience??
Captain
Lots of thoughts...no experience. ::)
There were a number of articles about it in Mother Earth News back in the 70s. Interest seemed to die out when cars started getting better mileage.
I'll see if I can find out anything from our County Agent about the Gov't program that installed some around here. They may have done the same in your region.
Simplist is the plastic-vinyl bag system. They sell down here at the larger hardware stores.
Ones we set up had a tube system where you dumped the goodies (bedding is BAAAD) into a small pit, and shoved the goody into the tube that was angled to below the surface of the slurry.
Other end had the overflow. You need a constant movement of spent slurry out of the digester.
Metal tanks were used for the slurry and the retention of the gas. As commercialized as Mother Earth Mag has gotten, they still have good info and simple construction ideas. Google them. Paul_H got his Wood-Gas info from them.
There's more to making and using the gas than most think. You are probably aware of the corrosive effects that need to be dealt with, EH ??? ;D :D :D
I saw a setup once used in a third world country once, it was basically a 6' diameter tank with one end sawed off it rested over another half tank that was slightly smaller and would slide into the larger tank like a hydraulic cylinder. There was a seal between the two.
The system would be charged with organic material (mainly from pigs and vegetable material) as methane was produced the top tank would rise and provide pressure to push the gas to the appliance (normally a cook stove)
Not sure how much gas volume you'd need for a generator but I imagine it would be fairly large, you could speed methane generation by providing a churning action where bacteria at the bottom of the stack was more evenly distributed and providing a little air through the stack to keep the temperature under the killing point for the bacteria.
You might want to look at some methane generating dumps, I've seen diagrams and cutaways online. It shows the churning process and explains how they get the best methane production.
Good luck!
You need to stir the mix, like Modat says. An additional reason is to break up the crust that tends to form on top, trapping the gas beneath it. I'm thinking a small hydraulic motor inside the tank would be the best option to power it. You can't put an electric motor in there :o, and you wouldn't have to worry about running a rotating shaft through your airtight tank.
I'm sure I'm going to butcher his name but try googling Ram Bux Sing or Gobar gas plant.
He was a fellow in India researching and building methane plants in the Mother Earth days.
There are 2 colonies of bacteria that make methane from my understanding. The least productive ones work at earth temperature, the more productive ones work in the mid 90'sF. One setup I saw in the mag back then was a compost pile built around the digester to keep heat up in winter. I had a civil engineer neighbor that looked into it for a municipality and the even heat requirement was a problem.
As a plus the bacteria are supposed to be nitrogen fixers so they make better manure than homemade ;D
I have a copy of The Back Woodsman that has a methane generator in it. Basically it is a concrete tank with a PVC stir stick in it. They use innertubes for storing it. If you would like the mag I'll send it to you.
Here's the Patch-Whitney generator from Mother Earth News. March/April 1975 issue.
Patch-Whitney methane digester (http://www.motherearthnews.com/Green-Home-Building/1975-03-01/The-Patch-Whitley-Methane-Generator.aspx)
Here's what you really need, electricity and methanol, just using sun, water and air.
http://pesn.com/2005/08/02/9600142_IAUS_Solar/
Captain,
Check out http://journeytoforever.org/biofuel_library/MethaneDigesters/MDToC.html.
They have an article on methane generation using something like an old propane tank or something like that.
Info on that JTF Site is not very accurate, at least for the Biofuel. MOST folks have problems using their info. ::) ::) ::) ::)
I built a little pilot methane generation plant...
Worked enough that I plan to scale it up when I finish building my house.
here's a link to the description...
http://massiehouse.blogspot.com/2006/09/butt-holes-contributing-to-self.html
yes, I think the key is the materials handling aspect of the whole deal...
as you can see, I did not spend much time perfecting that aspect of the working model...
(https://forestryforum.com/gallery/albums/userpics/13971/pouring%20manure.jpg)
-Thomas
Man, and I don't see a paddle anywhere in sight :D :D
Edit;
I noticed a comment and woke up to a tragic news report this morning. Methane is heavier than air. A farmer entered a manure pit to unclog a pipe, he was overcome within seconds, his helper did the same, then his wife, then 2 daughters. All were overcome in seconds. They leave the youngest 2 behind. Be careful!
I always thought that methane was lighter than air. ??? Propane is heavier than air and pools in the basements. If methane was heavier than air then it would not affect the ozone but the low areas would be deadly. :o
I am sure that the family was killed by pit gas which is similar to silo gas. It is very deadly.
Farmerdoug
I thought methane was lighter than air as well, I thought I saw a myth busters show where they bubbled methane in a soap solution to mape a floating column of floting bubbles then they ignited it in typical myth busters fasion.
I searched for gas in manure pits, and the following indicates there are four, one of which is methane (but it is dangerous for being explosive) and said to be lighter than air. More mis-information from the press. :) They need to get Jeff to help edit their stories. ;D
Gas in manure pits (http://www.nsc.org/library/facts/agrigas.htm)
Probably not the methane gas, which was blamed. One article quoted the Sheriff as saying they couldn't rule out drowning (yuuucckkk!) or that the original person in the pit didn't have a heart attack, then the others followed in to rescue. Probably never be known.
There also is Hydrogen Sulfide, Ammonia, and Carbon Dioxide gas, according to the source listed.
And as mentioned, likely similar to silo's gas, but nitrogen dioxide is one that is prevalent in the silo. Most of the gases cause a shortage of oxygen, thus suffocating occurs.
My guess is that it's the hydrogen sulfide that was the culprit, it is very deadly. We see a few deaths every year in hog country with similar results. One goes down and the others trying to rescue are overcome also, very sad.
CH4 (Methane) is DEFINATELY lighter than air. I suspect Norm is right.
Captain
All said and done, enclosed spaces with rotting and fermenting matter are dangerous places to go.
Farmerdoug
Especially bathrooms ::) ;D
I hope you have better luck getting the power company to agree to buy from you than people in Maine have had in spite of the law that says they have to. And that is if you have 3 phase power available on the utilitly pole and if you are willing to spring for the matching transformer, reverse power relay, underfrequency and undervoltage protection relays and whatever else they've deemed necessary to have since I looked into doing this.
In Michigan, local utilities are required to buy your power but only to the amount you buy. If you produce more you are giving it to them free. ::)
Farmerdoug
I think those are called PURPA laws if anyone needs to look them up.
For anyone interested. Back in the 70's, the New Alchemy Institute of Falmouth, Mass. was interested in all sorts of alternative forms of natural energy and such things. Their libraries were filled with all sorts of Empirical Data from experiments they did. One of these I was interested in was a technique developed by a Frenchman by the name of Jean Pain. He had an Institute in France dedicated to creating methane gas from wood chips. I read his Manuel so many years ago
Essentially, you take very small diameter deciduous trees with lots of foliage; chip it; put into a tub grinder; mulch it again, then lay it out on a slab of some hard material and soak it with so much water that it will not retain any more. Pile it into large specifically designed piles with 2 strands of PVC running in concentric spirals with in this pile. One for air, one for water. The results were 180 degree Fahrenheit temperatures. Also within this system, a slurry tank was installed in such a way that you would use small amounts of composting material to create pressurized methane gas, which Jean Pain then modified all his vehicles to burn. I believe you can get info on this from the Jean Pain Institute. Check it out.
Enchanted Forester