methane

[annabella1]

Lately I've been studying about methane for power generation. Most people are using continuous digesters to produce methane from animal waste. But in my research it appears that a lot more methane for a longer period of time is produced using plant materials in a batch or "sump" digester. I also have been looking for ways to produce power from methane, and found that anything that uses natural gas will work with methane. I think it may have been suggested here to use a lawn mower engine with a car alternator to produce power to charge 12 volt batteries. The methane can be introduced through the engines carborator, and the gas tank can be retained for a back up energy source. While I was searching around for this I found an article from the 1970's in Mother Earth News about a guy who used a lawn mower engine, an alternator, a bank of batteries and an electric jet engine starter motor to run a car and was getting 75 MPG. I don't see why this couldn't be done with methane and using fork lift electric motors and batteries? This would make the power almost free and definately from a renewable source.

[kawalekm]

Hi Annabella
I have a book at home entitled "Home Power". *When I get home tonight I'll try to get the title, author, and publisher for you. *There's a whole section on methane production. *Methane can be produced in a digester much like a septic tank, and the gas is plumbed to a novel storage tank designed to hold gas at atmospheric pressure. *

I've read you have to control the temperature of the fermentation closesly, because the methane producing microbes are thermophiles. *If the digester cools down, only CO2 gets produced. *By the way, the gas that gets produced is only about 2/3 methane at best, with 1/3 CO2. *When things aren't working, you get 100% CO2.

One added plus is that it's a way to dispose of all your waste, even excretement, and drasticly reduces your garbage. *You only have to recycle your glass, metal, and plastic to be almost completely waste free.

For power generation, I think your best bet is to get a dual-fuel generator that uses either gasoline or natural gas. That way you already have a piece of equipment that you know will work right with your methane without a lot of juryrigging.
Michael

[MadTripper]

I have access to a generator that runs on gasoline but can be converted to propane. Most devices that are propane can be converted to natural gas and vice versa with the change of an orafice plate and modifying the air intake. So.....I wonder if you can go between methane, propane and ng easily. The generator I speak of is 90KW which is gigantic but might be an interesting project.

Tripper

[chrisser]

Annabella,

I've seen that Mother Earth article for a basic hybrid-electric vehicle.

I've been researching such a thing on and off for several years. *It seems that there just aren't a lot of home builders making them - plenty of "regular" electric vehicles out there.

I think what holds up most people who have the idea is lack of an easy-to-obtain alternator. *

There are plenty of traction electric motors capable of powering a vehicle. *I've noticed they tend to run generally on 144 volts DC (a bank of 12, 12-volt batteries) and can hold enough charge for most home->work->home commutes. *Most people could live with something like this, assuming they have the power capabilities to charge the vehicle overnight, and plenty of homebuilders make do.

For many people, though, the capacity to exceed that "typical" drive occassionally is a requirement, and two cars means twice the insurance, maintenance, space, etc.

A hybrid-electric system could be a solution, using a small gasoline or diesel (or alternative fuel versions of either) to power a generator/alternator that could either recharge the batteries, or, ideally, be able to power the vehicle on its own on long, continuous speed trips, and use the batteries for short trips and acceleration surges.

Of course, EVs are already pretty heavy, and adding an engine and alternator just makes that issue worse.


I'm just a hobbyist, and although I have a basic understanding of electricity, i'm no engineer, but...

I've often wondered if one couldn't take a small four-cylinder engine, like a GM Ecotec, or something by one of the Asian manufacturers, or a small diesel, and use it to power a bank of standard automotive alternators at a constant speed.

You could electrically tie each alternator to its own battery in the bank - so for 12 batteries, you'd have 12 alternators. *Then run your traction motor off that.

For short trips, you'd have a pure EV with the engine off, and you could charge the battery bank at night. *For longer trips, you'd be running off the small engine at a constant speed, maximized for efficiency at that speed. *When you need to accelerate, the batteries would be fully charged and could be discharged as needed, only to be recharged by the excess power generated by the engine/generators. *If you're not able to charge the battery bank, just leave the engine running while the car is parked and it would top off the battery bank.

With something like that, you could match the small engine to whatever fuel(s) are available at the best cost. *You could even charge batteries overnight if that was a good option. It might give better efficiency, lower pollution, higher flexibility and you might even end up with higher performance if you selected the right components. *Weight is an issue, but its also a benefit (to a point) for handling, especially if you get the center of gravity low (which is much easier with batteries and an engine that doesn't need to be hooked up to a drivetrain).

I think it would be awesome in a mid-size pickup (pickup trucks tend to have a lot of unused space under the bed).

[MadTripper]

I'm probably a bit ignorant here but I wonder about the total efficiency.

Knowing that there is no perfect system, be it electrical or mechanical, how is the trade off from running a high efficiency gas or diesel to electric?

A test scenario would be like this:

Take the energy consumption of a fuel efficient vehicle and produce a standard unit for comparison (be it gallons/hp, gal/mile or whatever). *Then provide a generator to charge and electric car with similar or better efficiency. *Would the fuel consumption be better on the generator or worse? *Is there any studies about this? *I know electric hybrids are gaining popularity because of the emissions situation however are people even considering the increase in electrical requirements from the grid to charge their vehicles? *

From a self-sufficiency standpoint, you need fuel to provide either the engine or the electricity for the motor.

In college we had a project to design an electric car. *Mine was using the body and frame of a 65 or so AC Cobra that charged on a downgrade or when brakes were applied. *Of course this extended the running time but eventually you would have to charge from the grid due to inefficiencies.

So where a gas or diesel converts to rotational energy directly, (albeit not tremendously efficient), an electric vehicle must have the energy converted from fuel, to electricity, trasfered to a storage bank, then transfered to rotational energy as well. *Seems like the extra steps add more resistance thereby decreasing the overall output per unit.

I'm not really sure either way but I thought I'd bring it up for thought.

Tripper

[chrisser]

Tripper,

I really don't know. From what I've read, that appears to be the consensus - that the efficiency gained by running a smaller engine at a constant speed, less the inefficiencies in converting the mechanical energy to electrical, and then further storing and retrieving it - as a system, exceeds the efficiency of an internal combustion engine.

Primarily due to the huge inefficiencies experienced during acceleration, and a little during idling, as I understand, with an ICE.

It does also make pollution moderation easier with a fixed speed engine.

Personally, since gas, when adjusted for inflation, is still not all that expensive historically, I've always been researching something like this with a goal of building something with equal MPG to a current vehicle, but wildly better performance and less pollution.

Electric motors produce nearly 100% of their torque at 0 rpm. What a ride that would be on a machine with a very low center of gravity.

But the principles are probably applicable to the other end of the spectrum - maybe with a little of both...


P.S. Anabelle, I'm sorry I sorta hijacked your thread on methane by running off on a subtopic.

[MadTripper]

I apologize as well but it kind of fell into place. *I wish I had a test bed to further research but wow, would that be a project and I have a hard time believing the major contenders in the industry haven't looked into the whole process, but then again, they have the ability to produce a product that looks very friendly from the buyers prospective passing the energy requirements on to a whole different arena of production.

Tripper

BTW, I realize that if you were using hydro, solar, or wind power you could easily beat a combustion engine. *That takes the pollution out of the picture and since mother nature is kind enough to donate the initial energy, the end result is free regardless of the efficiency.

[AlchemyAcres]

Lately I've been studying about methane for power generation. Most people are using continuous digesters to produce methane from animal waste. But in my research it appears that a lot more methane for a longer period of time is produced using plant materials in a batch or "sump" digester. I also have been looking for ways to produce power from methane, and found that anything that uses natural gas will work with methane. I think it may have been suggested here to use a lawn mower engine with a car alternator to produce power to charge 12 volt batteries. The methane can be introduced through the engines carborator, and the gas tank can be retained for a back up energy source. While I was searching around for this I found an article from the 1970's in Mother Earth News about a guy who used a lawn mower engine, an alternator, a bank of batteries and an electric jet engine starter motor to run a car and was getting 75 MPG. I don't see why this couldn't be done with methane and using fork lift electric motors and batteries? This would make the power almost free and definately from a renewable source.

Ever heard of Jean Pain?
He's one of my heros!, but dead and gone now!
:-[
Anyway....in a nutshell...the heat from large compost piles is used to heat a home (or whatever)...the methane released from the decay of the compost is collected for cooking, etc. etc. etc.

http://www.motherearthnews.com/Organic-Gardening/1980-03-01/The-Genius-of-Jean-Pain.aspx

http://journeytoforever.org/biofuel_library/methane_pain.html


TMEN also did a 3 part series just dealing with the compost heating of a home, greenhouse or other structure...
The (now defunct) New Alchemy Institute published some great info on compost heating and methane...likely still online somewhere...

~Martin :)

[annabella1]

I looked up Jean Pain after you posted and that is exactly what I am talking about. The problems they are having with methane and co2 production are mostly from manure source methane. Methane from plant sources produce 75% to 80% Methane with a small amount of co2 and a small amount of hydrogen sulfide. While the methane produced from manure plays out in a matter of weeks. Sump (Batch) digester filled with plant materials will continue to produce for over a year. What I thought of is using the aerobic combustion of a compost heap to regulate the temperature of an anaerobic sump digester filled with plant materials. To further control the temperature you could place the compost heap covered sump digester inside a greenhouse. I have read of people heating their homes with water heated in hoses run through the compost heaps enclosed in a greenhouse.
In the article about Jean Pain it mentions that water was heated in the compost heap he had surrounding his digester. I know that the co2 can be removed from the gas produced by bubbling it through Lime water. Also the hydrogen sulfide can be filtered using iron filings and wood chips. All the resulting waste will make excellent fertilizer and compost. And Methane is a very clean burning fuel.
I think more attention has been paid to Methane produced from manure sources because the manure is a problem that they need to get rid of. But plant based methane production is far more efficient.

[annabella1]

Oh by the way chrisser the subtopic of the efficiencies of the engine is fine by me. I agree with you. Originally I thought it would be best to run the methane in the air intake of a diesel engine (I had read that the speed of a diesel was appropriate to methane) but then you had to somehow introduce a spark, (methane needs a spark) and regulators. Then when I read about the efficiency of the small constant speed engine and someone here had suggested using a lawn mower engine and alternator. Then I read about the car in Mother Earth News it kinda all fell into place. I just wish I had a place where I could put it all together I don't think my brother will let me do it in the bedroom I am renting from him.

[annabella1]

In the Jean Pain article it mentions that he used shredded wood at 1/16th of an inch. I hadn't thought of that it would make the composting far more efficient. Since I don't have an acre woodlot to harvest the undergrowth and trimmings. I wonder if shredded newspaper would work. I know that there is a lot of paper waste in my suburban neighborhood. I already use it in my vermiculture bins.

[SolarGary]

Hi,
The New Alchemy paper that Martin mentioned is here:

http://www.builditsolar.com/Projects/Sunspace/NewAlchemycompost.pdf

Its quite good.

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

More heat from compost here:
http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#GreenhouseHeat

Gary

[MadTripper]

Thanks for those links both Alchemy and Solar. There is some very interesting information there.

Tripper

[kawalekm]

Hi Annabella
Sorry it took so long to get back with this reference. It's "Producing your own Power" edited by Carol H. Stoner, published by Rodale press. Section four of the book gives details on constructing, maintaining, and utilizing a digester.

[johnjmw]

Annabella,

I think the real problem is what you have on hand to digest. Manure is a common waste on most farm with a problem with the odor. Digesting it turns it into compost faster and reduces the odor problem. This is one area where pig farmers really have problems. By digesting the "waste" they gain electricity and don't annoy the neighbors as much. Cattle farms and Dairy I am sure have teh same issue about disposing of waste.
Did your sources mention that there is a problem with a scum cap that hard to decompose cell membranes cause that need to be remove or it will solidify enough to halt digestion. The hay/straw in manure still causes this problem but the continuous digester usually can handle it better. It's kinda like a wax like substance.

[annabella1]

The scum cap you are talking about is usually a problem with the fatty residue of animal wastes. The plant based digester has very little of this problem. When the fat from the animal wastes mixes with the straw and bedding waste it floats to the top and hardens. When you use plant based materials they are shredded into smaller pieces and do not have an excessive amount of grease.