Biogas - small scale production

[wooliver]

 Thanks for the comments.

Bruce, i can't get your e-mail to work on my machine, probably too many odd characters (my fault).

kurt, thank you. That's very interesting. I've got just the regulator to try that on.

The initial drawings are going to be history soon. I feel like i must simplify and go to a system like the ARTI "tank in a tank," if i want a continuos process.

Evidently the telescopic part where there is no seal between tanks cannot produce anearobic bacteria because of the presents of air in this area. It also seems optimum to minimise this area, as it is waste. The ARTI system uses poly tanks. I'm looking at poly trashcans, or ashbins. Larger than buckets, and available cheaply and in many sizes. The bungs are available in ag stores, in the sprayer dept. You can put a bung in any reasonably flat plastic surface.

What i've got presently, i don't want to waste of course. I've got a tighter fit for the inverted bucket in the water, than the present 30gallon ashbin. So the guide and the inverted bucket will be the smaller of two digestors. The larger digestor will incorperate the 30 gallon inverted (it's already plumbed) into a 50 gallon ashbin.

OK, about heat: The easiest thing to heat is air. The most efficient electric thing is the muffin fan. I even have a DC muffin fan i could run on solar charged batteries. So i'm thinking about an insulated airbox around the digestor, and a thermostatically controlled ducted muffin fan. I can duct it to a rooftop solar collector or a methane burning heat exchanger or any source of heat.

For this stuff to flow etc. i'm also looking into mascerating pumps like they have as an option in the RV world. They are DC i think/hope. Borrowing a surplus blender from the kitchen seems like we're back to making batches and burning juice and time. But this is what the critters teeth do. The feed must first be insized, then ground. Did you ever put grass in a blender? i think it would work with some water. My intensions are to feed this grass and distiller's grain. This is what we have.  The corn is so high priced today, they couldn't get a bid on pigs today at a nearby salebarn. Recently they were raising hogs for the manure alone. Now it's too expensive to feed the pigs. Thanks again.

[Bruce S]

I have changed my user info to be slightly easier. I don't get that many spam stuff anyway, who knows I may need that office 2009 someday...

The can-in-can system is easy enough to work with, plus if that's what you have why spend money on something else ? You can upscale your output as you need it by merely starting another if needed as well. The cast-offs are really good for feed intensive plants like tomatoes and Okra.

grass: nope never thought of blending grass. What I did was to get a mulching blade and put it on my electric mower, and run it through there a few times. Works great for getting a compost going too.

How much of this dry/wet grain can you get? I know from reading your pretty close to a ethanol plant I believe.

For pig slurry, you don't really need grain they'll eat about anything, least the ones G-pa had did.

I digress; the slurry, how thick is the load you've been testing with? how's the PH?

I'm thinking muffin fans will work nicely, you could wire them up to pull heated air from a collector mounted where the sun can heat it, may be good to have it closed loop too, since you'll not have to worry too much about freezer the air. One big air loop around the tanks and back up to the collector.

If you have old VCR or VCP around, you can grab the loader motors out of them, they handle starting all they way down to 3Vdc and speeds will be according to the voltage available.

Insulation would probably go further to keeping things warm. Insulation from the ground would help , so it doesn't act like a heat sink.

Cheers;

Bruce S

[ghurd]

Gas would have to be $95/gal for me to deal with pig-poo any more than I already have.

M.E.N. had an article about pig-poo methane back in the late 70's / early 80's.

It talked about the seals / moisture / solidification-of-the-surface materials.

"South Africa" comes to mind.  The number "83" comes to mind.  Not sure why.

Also "tractor" with "propane".

Forgive me if it has been mentioned in earlier posts.  Much easier to follow if everything is in the same place.

G-

[Bruce S]

[TomW]

Yeah, opening a fresh Diary for each new thought does make it tough to track progress of the dialog, especially later on when folks are trying to follow your stuff.

Tom

[wooliver]

For some reason i could no longer add to the last diary entry thread. Hence new entry.

No, not using hog poo. Using cattle poo, but only for starter. Same feelings about hogs. My comment was toward the strange economic unbalance at present, locally.

latest iteration of design:  

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

Why is it when miners find a big vein they suddenly disappear?

 

[TomW]

wooliver;

For some reason i could no longer add to the last diary entry thread. Hence new entry.

Not to divert the thread, but I went over and checked those Diaries to see if they somehow got comments locked out. That has happened a couple times due to a bug in the forum. They are fully open to comments as far as I can tell.

Then, again, the board is a bit twitchy lately.

No big deal, really but just makes it easier to follow along in one place for later readers.

Tom

[brkwind2]

Someone told me there was quite a bit of interest in using methane on the farm many years ago until they blew up the research facility & then everyone lost interest.  I too have seen more poo than I care to remember since I was the cheapest & most convenient one to have scoop it when I was a kid, apparently.  

The company I work for now treats all their waste water themselves & has covered one of the lagoons with a rubber membrane & we burn, I believe around %25 methane in one of our boilers.  I wonder how much methane my septic tank produces?  I've heard more than one claim I'm full of it.  

[domwild]

Have read an article about Chinese systems. They use iron filings to bind the nasty H2S that is in the methane. Can no longer find the article for you. Sorry.

[elvin1949]

  Tom

 At least they are numbered.This one is #3.

later

Elvin

[wooliver]

Gone to the bucket-in-a-bucket design. Makes it contiuous, bigger capacity too.

i just gotta let it sit and work.

[elvin1949]

  I to have read about using iron filings to filter out the H2S.Been a while so also can't remember where it was.

later

Elvin

[wooliver]

more issues and thoughts;

Like animals this thing needs be watched and possibly fed by somebody that knows what he/she's doing. If you go on vacation, simply cooling it down will slow the process, but could you completely kill it? i don't know, but it's slow to start up again. An unknowing watchman could easily overfeed it and cause and acid condition, taking time to remedy.

The plan was to gradually compress a storage tank, but i wouldn't leave this completely unattended. So if you can't bring it with, it raises questions about somebody that is not home much, just how this would work. More thoughts on this later.

Whatever you put down the ad pipe needs to be able to sink. Elsewise you have to come up with a way to crowd the food into the bottom of the digestor. I'm testing wet distiller's grain. It's 75% water. According to my brother, it spoils fast, so im thinking it's readily digestable. But water is water. And water has no calories. In fact it dilutes whatever does have calories.  To date i've not added wet distiller's grain, but i've got my sample ordered. It must be heavier than water, so possibly 50 lbs. per 5 gallon, so that could be more than 50 days worth of food/fuel. I still don't know what they charge for this stuff, or if they'll charge for 5 gallons every two monthes.  

Bubbling the product through water to filter and remove some of the H2S04. I believe i'll make a water collumn out of a 2" PVC pipe 2 or 3 feet long. Draw my gaseous product through with the vacuum generated by the compressor intake.

Note this compressor is aluminum as apposed to iron.  If the reaction is great enough to develope the proper pressure i could still add the inverted bucket in the water storage as well, as the headspace available in the digestor itself.

back at it.

[Bruce S]

Your first thought is dead on!!

I'm going on vacation and stopped all unautomatic processes, which means even the alky is stopped.

On adding food, you could build the unit to add the incoming so that gravity fed leads it under 1/3 from top, this should help with mixing and keep that crust cap from forming. A drill powered paint mixef pushed in could help as well.

Wet distiller's grain: You should be able to get a full report of what's left. Usually they are high in protein, since they're after the starch.

since water is about 8lbs/gal ... you can deduce how much true feed stock you're getting.

Cheers

Bruce S

[wooliver]

Biogas production report:

785 cubic inches (.45 cubic feet) can be produced in 48 hours. Good burnable product, so far.

The moped takes .353 cfm @ 2000rpm.

A 1300cc car takes roughly 4.75 cfm @ 2000rpm.

 For a 20 minute ride, I need about 960 hours (40 days) of production. This is figuring the moped running .45cfm as apposed to .35cfm figuring for simple waste.

So simply put, I need to scale up at last 40 fold.

Concentrating on heating now:

I have an old RV furnace i'm revamping, but i'm also inverstigating resistive electric elements that i can encircle the barrel. Could be better heat & transfer for the wattage.

[DamonHD]

Well, very interesting to get some engineering numbers like that out.

Do you think that scaling up is do-able?

Rgds

Damon

[wooliver]

For comparison, here are some anicdotal number from the ARTI biogas plant:

The system is 2 meters across by 2.5 meters tall. They boast of 250 gallon (about 33 cubic feet) daily from 1kg of added feedstock, once the process starts.

More engine sizes vs. consumption:

125. cc = .44cfm @ 2000rpm
     
250. cc = .88cfm @ 2000rpm
     
     

So the smaller the engine the better. But that goes with any fuel.

 

[wooliver]

Of all the messing around to date, this is what I'd build:

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

Presently, I've got the barrels, but heating is still a small obstacle.

30. gallons = about 4 cubic feet
    
125. cc = .44cfm @ 2000rpm
     
     

(double that for a 250cc of course)

a 20# tank @ 250psi = 157 cubic feet & should yield almost 6 hours running for a 125cc.

Y'know it does smell a little. But it smells like the cattle barn at the Fair. The way I look at it, it could be much worse.

[wooliver]

Update -

Production has increased and odors have decreased. Remember i only started with 1  shovel of wet cattle manure and 3 shovels of grass clippings. I've since been feeding it mower fines and grass clippings that have fermented in water for a few days.

I've successfully run my 50cc yamaha right off the barrel. Unfiltered with 3in.WC head pressure. Pulled the fuel line off and replaced it with the biogas hose, instead of placing the biogas hose in the intake stream. My hopes were to achieve some sort of throttle control. No. The engine only runs at one speed. I've read the modifications that can be made to standard regulator, but i've opted to purchase a regulator designed for throttling. More on that after install.

Rather than upscale production, i've concentrated on filtration and storage. I've rigged up a York/Tecumseh auto AC compressor for evacuating and pressurising tanks.

I've got a glass gallon jar filled with water and a foam final filter i draw the gas through as it's be pumped into a storage.

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 .45 cubic feet @ 3 inches WC. Or 1.35 cubic feet at less than 1"WC.

That's 405 watts daily, possibly.  Currently using 500watts for 12hrs a day.  That's 6kw/h x 8 cents.

Review with corrections:

50cc (2cycle) @ 2000rpm consumes .353cfm. So a roughly a days productions for 4 minutes. 20 minutes round trip to town would be 5 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).

[wooliver]

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.  That's just about every day. They rate nat.gas at 300w/cubic foot. I can't see why this wouldn't rate similarly.  

[DamonHD]

Wh, not W!

(31.5kWh per 100cuft is what I'm billed for, for 'standard' UK mains gas, BTW.)

Rgds

Damon