Methane Biodigester – How To
transcription of “Methane Biodigester – How To” video..by The Urban Farming Guys..
Today, we’re gonna bring you into the world of bio-gas digestion. The whole idea is to create methane, just like you do in your stomach; as you’re churning up your food, one of the bi-products is methane. Here, we’re gonna show you today four different ways. You can go as simple or as high tech as you wanna go with this. Here’s one real simple method right here where you take two cylinders.. & as you put food waste & your manure & everything else in there, as it churns up, the methane bubbles to the top & forces that upper cylinder up, which is good for several purposes. It holds the methane, it pressurizes the methane so you can send it back to your utilities or whatever you’re gonna use it for.
So, you put in your rotten vegetables, & your manure, & whatever you got ground up you put it in here. This isn’t built yet, but you’ll get the idea. & it goes down to the bottom, & as methane builds up under this chamber, it raises up slowly like this, til it would eventually fall off. So, you build a cage to keep it from falling off, & then as you use it, as you turn your cook stove on or your generator, this thing goes back down by itself. This is kind of a proof of concept. Right here, we’re gonna do the same thing, with a much bigger scale. We got these old fuel tanks on a farm, had them welded together, made one a lot bigger..They just happened to just fit inside each other.
So, here’s another concept. Here’s a whole other way..The whole idea is to have a sealed chamber that seals off the oxygen. This is what we’ve done right here with these three tanks. This tank right here, you put the food scraps in here. This thing grinds them up & sends it down this pipe & the food just rots. It’s sealed. The whole idea is to starve the rotting stuff of oxygen. It’s anaerobic composting. Now, I’ll get into the science of that later. So, after we cut the top off of our trash can, what you have is a free hula hoop or a jump rope..Gotta get good at it first..
Here’s the top of our trash can. We’re gonna use the uniseals again. We drilled the hole here, got our uniseal here, pop it through. There may be a better way to tap into here, but I had a uniseal so I’m just gonna use it. They’re not too expensive. Pop our PVC right through that hole & that will cause it to seal when it expands.
We’re gonna take these rotten apples & rotten vegetables & turn them into methane by grinding them up in this methane digester & letting them rot. First, we’re gonna turn on the water here, plug it in; later, we’re gonna put a switch on it. Whew! Nasty! This is a 3/4 horsepower insinkerator. Take a look down here, as I’m grinding. So, I just ground up a whole box of apples in like 30 seconds to a minute, straight applesauce. The great thing about using rotten vegetables is you get there before it’s halfway digested. A lot of people use methane digesters; they’ll throw cow dung in there, which is good. But, that stuff is halfway already used; the cow’s already used it. One time, they hooked up a balloon to one of these cows. That cow, in one day, filled up a balloon full of methane the size of a cow. So, if your stuff is halfway digested, half the methane is gone already. If it’s fresh. Nothing produces methane like anything with sugar in it..cantaloupes, apples produces way more methane than just grass would. So, what you should do, you should go out to some of the local restaurants, you know the ones right down the street, & see if you can make a deal with them to get their leftover food waste to put in your biodigester. It’s way better than just using cow dung or chicken waste. There’s way more of it. We just picked up 800 pounds of food waste. You know, if it was good, we’d feet it to the chickens, but it’s super rotten stuff. We’re just tossing it in here, grinding it up, It’ll produce methane for 7-8 weeks. It’ll produce a lot of methane within two weeks. Within one week, it’s producing a lot of methane; the second week,a lot of methane, then it just keeps going for 7-8 weeks. By the time it’s fully digested, it almost comes out like a clear liquid.
This is our biodigester blueprint. These are our three IBC totes: one, two, three. I wanted to build something that’ll take a hundred pounds of food scraps a day, move it on through. Then, the stuff that’s been in there for a few days, will come off the top, go back into the bottom, swirl around. The stuff that’s been in here for a couple more weeks, will come off the top. Then, by the time it gets digested to the end, it’s almost fully eaten up & turned into a nice, clear liquid almost, that we can use for fertilizer.
Last thing we’re gonna do is install our overflow valve. We’re gonna put a hole right here & put this uniseal in right there. Shove this into the tank, & then we can come in & pull off about 100 gallons of fertilizer whenever we want it. We’re gonna pull off all these burrows & make that real clean. Use a really sharp hole saw if you can. I still haven’t had any problems though with my dull ones. It fits in there like that. Take this, fit it right in here. It’s not easy. So, we don’t want this thing flexing, so we’re gonna put zip ties on this side, zip ties to this side so it’s firm. We’ve already secured this side so we’ll go that way. Right now, it still goes that way. You gotta have zip ties; I use zip ties all the time. Put your uniseal in; slides in just like that. Save you $50..a 3-inch bulk-head fitting sometime you can spend anywhere from $30-75 bucks. This is $5. Then, push this right through the uniseal, like so. & you’ll wanna turn this in. That’ll give you an air-tight seal. & it just sits right on the bottom. We’ll add a funnel on top of this so you can pour the food waste right in.
Alright, wiring up our disposal here..
Here we are, going solar. We’re painting it black, to soak up as much of the sun’s heat during the day to keep that reaction going & simultaneously heat the greenhouse during the winter time. In the summertime, we’re gonna hate it..probably have to cover it with a white sheet or something..
Off the back of these tanks here, we’ve got the methane gas manifold. The manifold comes up out of the top of the tank, runs down, collects methane off all three tanks here–Boom, boom, boom. We’ve dry-fitted this right now & marked a line so that when we go to PVC, it’ll be easy.
Alright, now we’re gonna get into the science of this thing. What we found out on accident, I guess nobody told us or we didn’t read the last few lines—You can’t just throw a bunch of rotten vegetables & rotten stuff & manure or whatever.. you can’t just throw it into a chamber & expect it to just automatically create methane. You got several different variables & it’s really easy to maintain; you just gotta know some of the science. We don’t wanna make it super difficult. But, the whole idea is you got two different kinds of bacteria..One bacteria that eats your food & creates acid; the other that eats the acid & creates methane, a methanogenic bacteria. Then, you got two different kinds of food..You’ve got low-energy food, like what cows eat–grass; then, you got high-energy food like grain & at the highest levels, you got sugar. What happens is if you put too much high-energy food in your chamber at once, if you feed the system too much, you’ll end up getting too much acid-producing bacteria or too much acid. The acid bacteria will go crazy, produce a bunch of acid & that acid is great, it’s what the method-producing bacteria eat to create methane..The problem is that it shoots the pH so low…you know, once you get past 6, you’re done. Your methane bacterias start to die off; you gotta start over & build back up that methane population.
So, the question is, how do you start a methane digester? What’s the best way? The best way is to start it with cow manure. Now, not chicken manure; chicken manure has way too much high-energy grain, stuff that hasn’t even been digested that just goes right through the chicken’s body. But, the cow, they’ve been eating grass & it’s less likely to produce a spike in acid.
Right here, we’ve got a bunch of cow manure…A few hundred pounds of poop, stink, Mcnasty…that needs to be moved out of the truck & go way over there.. Can it be done? We believe that you are a part of the solution. We just soaked it up, filled it full of water. The whole idea is to start the process with this right here. Then, you add 5% or whatever you can feed your deal a day..you know, 5% of food scraps. & then, one thing you know, cows already have that methane-producing bacteria in them. You don’t have to find it, or wait on it or wait 3 months. One of the fastest ways to start your biodigester is to start with cow manure, horse manure. & then, you’ll be producing methane in no time cuz all you do is just add a little bit of whatever. If you wanna get going real quick, add some sugar. If you wanna be real simple, just get into a routine, get a solid stock going, add the same amount every day or get some pre-rotting stuff going..to where, you know, if you get a bunch of stuff rotting, you can pull off the same amount every day. You may not get the same amount every day; you may get a bunch at once, have it pre-rotting, producing a bunch of acid. Then, take that & add it to your digester. There’s ways to automate this to where you’re not like getting poop all over your hands, getting nasty..There’s ways to do this..
So, that’s it for our intro on bio-gas digestion. We’re gonna have another video in the future where we pipe this methane gas into a water heater, to heat the greenhouse, to heat the fish water. We’re also gonna pipe it into the house & use it on the gas stove. This here is the effluent off the digester. We’re gonna send it up to the University of MO & see what it’s good for. It’s supposed to be the process of digestion has cooked off any harmful bacteria; no chance of E. coli. But, we’re gonna make sure. We’re gonna get back with you on the results; tell you how fertile this stuff is. You know, if you have to dilute it, what’s it’s good for. & yeah, that’s it for this intro. The next one will be a lot more dynamic..
Okay, we’ve added some rubber bands around this Elmo, just to make sure she’s pressurized. Yeah, buddy!