Hello

[Bill2]

Hello. i've searched a great deal to find place where small scale methane digester ideas can be exchanged.

Less the insulating jacket, this is what i've got now-

http://elwood.longlines.com/~jonz/AD/MM_04X.jpg

It only produces about .25 cubic feet a day.

I've got the barrels for this -

http://elwood.longlines.com/~jonz/AD/digestor_7_10_08.bmp

but haven't started building. 3.83 cubic feet capacity.

Instead i've been building the equipment to harvest and store the gas.

I've got a York/Tecumseh auto AC compressor rigged up so i can evacuate and fill tanks.

I'm not into liquification as that get expensive. Presently i'm compressing to 145psi, but may go up to 250psi.

Why? To run small engines. I've successfully run my 50cc yamaha on this stuff, right out of the barrel. Just for test purposes only. I've set about removing the acids by bubbling the gas through filters for long term use and storage.

Not without obisticals, it gets cold here in the winter. Everything i've read says the best production is around 90 to 100 degrees F.  It takes 1600 BTU or 470w to raise the temp from 70 to 90 for the 10 gallons.  And scaling up doesn't effect consants. So i'm presently contemplating costs.  In the heat of the summer, it's taken me 6 days to produce enough gas for a round trip to town. It's been a fun project because it involves most every type of science and it really can be done. 

Cheers,

Bill2

[Alan]

Hello Bill

Your gas can escape from your collector and bubble up through the water on the sides.

By using a third drum you can collect 100% gas and the device becomes a storage vessel until you pump it out.

Regards

Alan

Having a bad hair day, picture gone missing. Will try and find

http://www.steamboilers.homecall.co.uk/Gas1.bmp

[Bill2]

i borrowed the design from the ARTI (India) system.  Actually the small portion that is exposed to the air can't produce the gas.  Anaerobic means without air. The usable gas acculates on top of the batch that is underneath the inverted barrel only, much like a neumatic cylinder.  This is also why, the feedstock must be added to the middle of the bottom. One could however digest in one vessel and store in another.

My first iteration was a batch at a time, but i found it easier to balance the diet of the digester if it's continous. If the ph isn't balanced in a batch, you wait.  It may never produce at all if you can't adjust it. But at the same time, the batch must remain devoid of air.

BTW im feeding it mower fines and/or grass clippings that have fermented a few days in water. Started it on one shovel full of cow manure, mixed with two or three shovels full of grass cuttings. I'm currently starving it to get a possible production curve or ratio.

[Ivan]

Very impressive! I've not heard of many people who have actually driven journeys on biogas, so you are a real pioneer!

If you know anyone that produces biodiesel, you could try adding their glycerin waste at 6%. This is supposed to dramatically increase production, but I haven't tried it personally.

[Bill2]

Thanks.
 Though i've found some on modifying a regulator for engine throttling purposes, i've broken down and purchased one.  This regulator essentially replaces the float bowl on the carb. More on that after instalation.

Alan's design is a good one. A clean water seal rather than an effluent seal would smell better in the pre-production period. Strangely, after it starts brewing, the odors is reduced much. It never stunk more than the cattle barn at the Fair. FWIW

more numbers: i found natural petroleum gas has about the same percentage of methane so i borrowed the wattage for some theory. By several sources, it's about 300 to 311 watts per cubic foot. Assuming this is at one atmosphere.  Daily production is .225 cubic feet @ 3 inches WC. Or .675 cubic feet at less than 1"WC.
That's 202.5 watts daily, possibly.  Currently using 500watts for 12hrs a day.  That's 6kw/h x 8 cents.

50cc (2cycle) @ 2000rpm consumes .353cfm. So a roughly a days productions for 2 minutes. 20 minutes round trip to town would be 10 days production at .50USD/day, or 5USD for a trip to town every 10 days. For comparison, i can still get just shy of 100 miles on a gallon of petrol, for under 4USD (so far).

Cheers & Thanks again

[Ivan]

Any chance of some pics of your digester and your bike? Also interested to see how you're introducing gas. Here in the UK, there is a well-established LPG market, so if I was doing the same thing, I think I would borrow that technology, as it's mass produced and cheap. I would fit an automotive gas regulator (includes a large diameter, sensitive demand diaphragm) and a 'mixer' which looks a bit like a gas burner ring which fit inline in the air intake as close to the carb as possible (thus retaining the ability to run on petrol when the gas runs out) - I can post pictures if you are interested.

[Bill2]

pix next week possibly.
The Yammy is not actually "converted."  I simply removed the liquid fuel ine and replaced it with the biogas line. One way to convert a small engine is to essentially dispose of the float bowl and add a hose barb to the bottom of the main jet. Then have a low pressure regulator to replace the float bowl. Another method, if you don't want to permanetly modify your carb, is to add a ventury plate. either before or after the carb. This website is quite helpful:

http://www.propane-generators.com/

Though this gas is lighter than air and disperses up rather than down as propane does, remember it's still quite flamable. I know people that have worked with LP or natural gas all their adult life with little or no incidents. These people were trained with safety in mind. I've said that if gasoline were a new invention, they would never legalize it because of the dangers. But it's what we're collectively familiar with. I'd handle a cubic meter of biogas, long before i'd mess with a cubic foot of gasoline vapor. If anybody is reading this with action in mind, i'd strongly recomend gaining knowledge of gaseous fuels and the handling of gaseous fuels. In the same way you'd study fire arms or explosives or anything dangerous. All the aforementioned can be put to good use, safely in the proper hands. I'm saying this, because of a recent comment elsewhere about this old technology. Some one said, paraphrasing,  "yes, i know of a guy that messed with that stuff and blew himself up, and that was the end of that."  When you hear my story you're getting an average of one. When you hear another story then, you've increased your sampling. Some will only expose good things. Some will only expose the bad. One must always draw his/her own conclusions. I so dislike rambles myself. My appologies.

B

[Bill2]

http://elwood.longlines.com/~jonz/AD/FULL_SYS_k.jpg

any .jpg with an underscore_k is new.

http://elwood.longlines.com/~jonz/AD/

Still producing half a cubic foot a day at slightly over 3" WC. Or 1.5 cubic feet @ 1 atmosphere. I feed it a handfull of fermented grass clippings every time i pump off.  Just about every day.

Cheers

[northern installer]

pix next week possibly.
The Yammy is not actually "converted."  I simply removed the liquid fuel ine and replaced it with the biogas line. One way to convert a small engine is to essentially dispose of the float bowl and add a hose barb to the bottom of the main jet. Then have a low pressure regulator to replace the float bowl. Another method, if you don't want to permanetly modify your carb, is to add a ventury plate. either before or after the carb. This website is quite helpful:

http://www.propane-generators.com/

Though this gas is lighter than air and disperses up rather than down as propane does, remember it's still quite flamable. I know people that have worked with LP or natural gas all their adult life with little or no incidents. These people were trained with safety in mind. I've said that if gasoline were a new invention, they would never legalize it because of the dangers. But it's what we're collectively familiar with. I'd handle a cubic meter of biogas, long before i'd mess with a cubic foot of gasoline vapor. If anybody is reading this with action in mind, i'd strongly recomend gaining knowledge of gaseous fuels and the handling of gaseous fuels. In the same way you'd study fire arms or explosives or anything dangerous. All the aforementioned can be put to good use, safely in the proper hands. I'm saying this, because of a recent comment elsewhere about this old technology. Some one said, paraphrasing,  "yes, i know of a guy that messed with that stuff and blew himself up, and that was the end of that."  When you hear my story you're getting an average of one. When you hear another story then, you've increased your sampling. Some will only expose good things. Some will only expose the bad. One must always draw his/her own conclusions. I so dislike rambles myself. My appologies.

B

well said,Bill2,its too late to think about these things when you are halfway to space without a rocket!!!(wheres the black face and frizzy hair smiley?)

[Ivan]

Thanks for posting the pics. It's smaller than I was anticipating - so really quite productive in gas, given its size. I'm thinking of making a unit out of an old hot water cylinder (120litre) - I wonder how much gas that would produce?

[Bill2]

Thanks Ivan,
  It kind of depends on the diameter of the cylinder more than the height. I can't really say how the methanogens stratify under the dome, but what i have found is that while i have a possible 12 inches of height to fill with gas before it starts escaping at the liquid surface level, i can let only half the tank get full before it starts to bubble out form under the inverted bucket. If i add more weight, it only tries to make the escape earlier.  This would tell me that the gas production is not only at the liquid surface, but even five or six inches below the surface. 

BTW under that 5 gallon washtub, is a brooder/heat lamp. Couldn't find the wattage printed on the bulb, but it must be less than 500 watts. One could run that through a dimmer and thermostat. Especially if this were all painted black and placed outside.

Good Luck

B

[KenB]

Bill,

What is the energy balance on having a large light bulb under the digester? 

I hope its not 500W, because that's like burning 24kWh (2m3) of natural gas back at the power station - every day.

This sounds like a good case for having it solar heated.



Ken

[Ivan]

I'm working on a variation of your design, based on an old insulated hot water cylinder. This should reduce heat requirements, and I can use the coil to provide heat from solar power. It doesn't have an integral gas-holder, so I'll need to feed this from the top outlet to an inverted-bucket style gasometer.

[Bill2]

Sadly yes Ken, it's about half of that. 
I was estimating a cubic foot of petroleum natural gas was around 300 watts. A cubic foot at less than 1 inch water collumn or close to 1 atmosphere has no real ability to flow, so i didn't think i could append any time (hour) denominator to it. That being said, if i produced half a cubic foot at 3"WC, that's 1.5 cubic feet at 1"WC. (Boyle's law) So if we were using 1 cubic foot at 1"WC per hour this would be a 300w/hr. Is this right?
And remember this is 24 hrs. production. My latitude yields about 4-5Kw per meter average annually. Not good really for maintaning a steady 90 degrees F. But so far, i've found this thing not to be as finicky as other's have reported. It cools down every night. I've let it cool for a week while i went on holiday. I just think the more one heats it the better, but better is the enemy of good enough. I read you can have the digestor heat itself, but from how one defines BTU's it's sort of futile to get steady heat.

Here's a design i call the "sandbox" digestor. I started out thinking of digging a pit.  The problem i can visualise about this is working with a thin plastic, trying to get an airtight port through it, and not tare it. Making the bag would be easy.

http://elwood.longlines.com/~jonz/AD/DIGESTOR_02.BMP

Later,

B

[Ivan]

This is the kind of idea I've come up with - feel free to suggest improvements.