In my previous issues of Taking Care of Business I discussed how human feces can be composted aerobically in dry composting toilets, and also how flush-toilets can be made sustainable. Today I want to look at another alternative, the Methane Digester (or digestor – according to my spell checker both are spelled incorrectly).
Methane? The greenhouse gas exacerbating climate change?
That's right. Letting organic matter decompose without the aid of oxygen produces methane, a flammable gas known for its distinct smell. We don't have to go too far to experience it, as this anaerobic decomposition may happen right in our bodies, where our intestines form an air-tight container to the decomposing organic matter. These farts that occasionally build up and escape in smelly clouds accompanied by the sound of the leather saxophone, are so benign that they're hardly worth the mention... in our species. (If it happens on a regular basis, there may be some digestion-related problem on hand. Otherwise you may laugh it off or light it on fire.)
In case of cattle, however, the emitted methane is more significant, due to their digestive mechanism, as well as larger sizes. Still, all the cows in the world are relatively low methane producers compared to the fossil fuel industry, especially with such innovative methods as fracking. And then there is the methane escaping from thawing permafrost, leaving huge craters behind, like this one in Siberia. Since methane is a greenhouse gas, just like carbon-dioxide, this recently released result of ancient fermentation is both a cause and an effect of climate change.
So How Can You Use This Gas?
By burning it, of course, just like propane, butane, or any other burnable gas. The idea is, if we are going to cook on a gas stove, it may as well be something that doesn't need to be mined from finite resources. Fermenting organic material in an oxygen-free space is not that hard, especially since our bodies already produce sufficient amounts of raw material. It just needs to be fermented a bit further.
The Things I've Seen...
I have come across two impressive cases of methane digestors I'd like to present here. One is noteworthy for its simplicity, the other for its efficiency. Although both relied on animal rather than human excrement, the variability between these two examples suggests a lot of leeway for experimentation. The designer of one of these systems even said he could imagine it feasible to produce cooking gas for a high-rise apartment building, by fermenting the human wastes of its residents. Sounds exciting, though I still need to see such a system in action... But let me start introducing the simple digestor:
The Best Thought-out Pig Sty
This setup was designed by a farmer, rancher, gardener, and tinkerer in Costa Rica. Even though he'd never even heard the term Permaculture, his design closes many loops beautifully. It's an ingenious way to combine corn, pigs, methane, and the kitchen stove.
I was quite amazed to see how clean the pig sty was. Of course, the guy pointed out, it gets cleaned three times a day, every time the pigs are fed. I first thought that was ridiculous, but he explained the reasons for this unusual practice. First of all, the pigs appreciate a clean floor (good for them). Also, it only takes about five minutes to hose down the slanted floor, and sweep all excrement with the uneaten corn-meal into the gutter on the lower end of the sty, so work wouldn't accumulate. Most importantly, though, he didn't want the pig shit to start fermenting in the open air.
All the slush washed into the gutter passed into a concrete basin, covered airtight by a black tarp. There it would sit, and be slowly decomposed by anaerobic bacteria, who as a byproduct generated methane. This gas stayed trapped under the black tarp, only a safety valve on top allowed excess pressure to escape. From there a pipe ran straight into the kitchen, where it was hooked up to a pair of burners. Using it was as simple as any gas stove.
The water that carried the material from the pigsty flowed through the digestor, and came out as a brown colored, nutrient-rich effluent. This was further diluted with water and used to irrigate the corn, which eventually became pig-food. The circle was closed, the corn grew like crazy, the pigs enjoyed a clean sty and literally more food than they could eat, and nobody had to pay for the kitchen gas. Simple, easy, and at perfect scale. The family of six did most of their cooking that way, except for certain delicacies that required wood fire.
Efficiency in a Less Suitable Climate
Costa Rica, where temperatures are fairly stable all year round, even in the mountains, is the perfect place for this sort of setup. The digesting bacteria don't like sudden changes in temperature, which would affect their population, and thus their efficiency at fermenting. The other digestor, however, was in the high desert of New Mexico, where outside temperatures would normally fluctuate between freezing at night and sweltering in the daytime. So how did its designer make it work? By thoroughly insulating it at night, and opening up the insulation to absorb the daytime heat. Also, he was living in an earthship-inspired home, which added to the temperature regulation.
The other thing about this amazing setup was that he hardly had any animals to produce fermentable material for him. About 10-15 chickens (he never counted them since he considered it bad luck) and a dog was all there was. A daily trip to the chicken coop provided a scooped dust-pan full of chicken manure, with ample feathers, straw, chaffs, and such bedding material. The latter part was important not only for its carbon-rich nature, but for the added surface area, which bacteria would populate. All this was washed down a modified garbage disposer, turning everything into a homogeneous slurry, and added into the digestor. Unlike the owner of its Costa Rican counterpart, he didn't want to waste even a bit of excess gas. So with help of a compressor, powered by a wind turbine, the gas was concentrated into a big round container, previously used for storing propane. And of course, the effluent from this digestor was also used to fertilize plants. Thus, he covered all the cooking needs of his 1-2 head household. Impressive for his location, and with only a dozen chickens!
Other Examples?
beyond Earthships, the other one detailing the Jean Pain method of composting. Both are highly recommendable readings. These are of course only two examples of the possibilities. Has anyone seen any others? It seems to me that the entire of idea is such a radical concept that it remains mostly unexplored to this day. All the more reason to go out and play around with it. Trying to find interesting related articles on Steemit, I've come across two by @ecoknowme, one of them looking
Also, here is a list of previous articles from my series Taking Care of Business:
I am familiar with the setup in Costa Rica. There is also one at Selva Negra in Matagalpa here in Nicaragua. I am looking into something like that here. You can run a Sterling engine off the methane and produce electricity as well. We have a German engineer here working on sustainable energy here in Nicaragua.
Yes, hooking up a generator to it is the logical next step. Jean Pain used the methane to fuel his truck, which is equally amazing. Haven't seen that one myself though... How big is that generator in Matagalpa? The one in CR you can see in the pic was a family household, with about as many pigs fueling it as there were people being cooked for.
The one in Matagalpa is actually a series of digesters. They provide fuel for roughly 200 families and for the resort. I am not sure how many animals they have but Selva Negra is self-sufficient and produces all food for the families that live there as well as for the resort. We stayed there about 10 years ago and were throughly impressed with the way it was setup.
Oh wow, such a big system...! It was about 10 years ago that I was there too (well, 9 years ago to be exact) but Selva Negra fell completely out of my spectrum. Haven't even heard of it. :-( Well, it's never too late to return. :-)
You have just reminded of another thing for my homestead with list. Thank you for sharing some fantastic ideas. I'm surprised this post hasn't had more interest.
I've heard this can also be done with standard composting, although manure is the best thing to Start it going.
@originalworks
To call @OriginalWorks, simply reply to any post with @originalworks or !originalworks in your message!
For more information, Click Here!
To enter this post into the daily RESTEEM contest, upvote this comment! The user with the most upvotes on their @OriginalWorks comment will win!Special thanks to @reggaemuffin for being a supporter! Vote him as a witness to help make Steemit a better place!
This post recieved an upvote from minnowpond. If you would like to recieve upvotes from minnowpond on all your posts, simply FOLLOW @minnowpond
Digestors are awesome, if you have the animals to fuel them.
Read an article on a digestor at a dog park used to run gas lights at night, but it cant remember the source.
Did recall one Id read about:
http://wisconsinwatch.org/2014/04/manure-digesters-seen-as-best-hope-for-curbing-lake-pollution-but-drawbacks-remain/
Gas lights run on doggie doo-doo? That's a wonderful idea, but it shows how we are just scratching the surface of possible applications of this great technique. I can also see the reaction: cute, but gas lights are so archaic...! Except in this case the resource is locally produced and would otherwise constitute an annoying waste product.
Anyhow, thanks for the link too! The first thing that struck my eye was: "Manure digesters cannot (...) remove other contaminants like hormones and anti-microbials." Then, how about not putting them in, in the first place? Digesters wouldn't remove radioactive contamination either, if it was polluted with it. As for the political hurdles... I'm not surprised. But come a major MAJOR crisis, and see how accommodating everyone gets, if it's not too late by then. :-(
Found it!
https://www.google.com/amp/s/phys.org/news/2010-09-dog-lit-poop.amp
It should be noted that there can be some dangers associated with digesters. Hydrogen Sulfide levels can be high and even deadly depending on the feedstock. This will vary from digester to digester, but can be managed if you are aware. Also fire and explosions are rare but possible.
They can be complicated to operate. It takes some skill. But they are useful and millions were successfully employed across China in the 70's at small farms.
Finally a solid 'digestate' is often wasted from larger digesters. Smaller ones might be scooped out from time to time. If human waste is introduced into the digester, the digestate it becomes a different class of waste material. At least in many jurisdictions.
Thank you for pointing out these important aspects to methane digesters. How can fires be avoided and is there a way Hydrogene Sulfide levels can be regulated?
Haven't heard about the ones in China in the 70's. I wonder why that went out of practice. Was that during the Great Leap Forward? I can see how a great idea could be ditched because it was introduced together with something that could not work, like backyard furnaces. Or maybe I'm completely wrong, but would love to hear it still.
It sounds like you've had seen or maybe even worked with some digesters. Would love to know more about it, what aspects you liked, what not, and why. :-)
The easiest way to manage Hydrogen Sulfide is by introducing some sacrificial iron which will react with the sulfur. High surface area is best. And if you have the means H2S levels should be monitored, or personal H2S monitors can be worn. A small amount of oxygen will also help to reduce sulfur but can also be dangerous.
I am guessing China got away from the digesters as farms got larger, and more of the population became urbanized. As I understand, they still employ digesters there but they are larger and fewer now. When the population was largely rural, more people relied on digester gas for cooking at home.
The lower explosion limit range for methane is 5 to 15 % approximately. Digester gas can range for 45 to 80% methane, so dilution of the gas to the explosive limit is what you need to watch for. This can happen outside or inside the digester through a leak depending on if the gas is positive or negative pressure.
I have been to digesters all around the US. I used to work for a company that would treat the gas prior to use in a boiler or an engine. Great technology, but 50% of digesters at US municipal treatment plants have failed due largely to poor operation or trouble managing sulfur etc. Digesters are often not a primary treatment thus they are an afterthought for many operators.
Sulfur will react with a wide variety of metal including parts of your engine if you have one. It is something you have to be conscious of cause all metal parts will wear when exposed to gas. Plastic is often preferred.
Wow, thanks for this detailed info, @n8msic! It really does sound like digesters are merely an afterthought, as you said, whether in China or in the US. Too bad, but that also means there is a huge potential to develop them, big and small, for animals and humans (and modify the restrictive regulations).
Congratulations @stortebeker! You have completed some achievement on Steemit and have been rewarded with new badge(s) :
Click on any badge to view your own Board of Honor on SteemitBoard.
For more information about SteemitBoard, click here
If you no longer want to receive notifications, reply to this comment with the word
STOPI have been looking into these for a little while now. There is a company that makes full set ups called homebiogas. There are also many diy ones online however very few address how to store gas for later use. We are definitely going to make one in the future but still struggling to figure out how to store it
Personally, I think storing it becomes important if you don't have a constant bacterial action going on, such as in the highlands of NM. I don't know how cold your winters get, but even then some good insulation should do the trick.
seems like a waste not to store the gas as it's made :/
You're certainly right... but I guess you'd have to compress it for storage, which requires energy. That, however, can be done in a sustainable way, so in the end it may be worth it.
I know the home bio gas system uses water or sand to compress the bag. You should definitely look at their system. I'm just having a hard time figuring out how to do it myself not having access to the materials they do
Just came accross this nice post, @stortebecker.
I wish we really could make more sense of our business. I think about the digestor from time to time, but not so good in cold weather?
Sure, they don't like the cold so much... but neither do we. Yet we can accommodate living in cold climates for ourselves, so why not for them?
True true. I'm sure there's a solution for that somewhere... I mean if it's in full sun inside a green house type thing, it may be warm enough no?
I'm sure it would be... I once visited a guy with such a contraption in the highlands of New Mexico: freezing temps at night, and hot and dry in the daytime. With good solar exposure and lots of insulation it worked like a charm.
Good to know. I'll reasearch to see if there is such contraption around the north east. Thanks