Don't know if this is somewhere else but had an odd thought the other day. I know that well made compost can generate 130+ degree temperatures so I was thinking about building a few 3-4 cubic foot size compost piles throughout the winter in my unfinished basement. I figure that the heat will help cut some of the cost of heating the house while I get a RMH built in the summer. Not worried about heating water as solar heating is going in soon (hopefully). Any ideas if this would work? Really new to composting so I have no idea. And no I won't be using manure or food in the house piles, all that will be in the outdoor one. Indoor will be mainly hay and wood chips.
I would imagine that wood chips and hay could never get into that ideal CN ratio zone that composters aim for. But I've seen static piles of chips get almost too hot at the center to touch. Only you know what kind of effort it would take to haul this stuff down and back up. That said, I think your two questions you need to answer are:
Is this the right scale? Are you producing 1000 BTUs when you need over 10 times that to heat your home?
What I'll effects are you bringing into your (almost completely closed off all winter) home? Carbon will come off the pile, but in what forms, and what other gasses, and at what levels? Are you welcoming termites or other things that don't belong in a home? What about moisture -getting enough in the pile, and keeping it from causing damage in your home?
Luke Groce: Trying to figure out how to grow food and heal land.
I thought I heard Paul say in one of the podcasts that hay has the perfect Carbon:Nitrogen ratio. Maybe I'm wrong. Hmm never thought about BTU amount needed. Have to do some calculations to see what a pile could generate. Wouldn't help if I needed a pile as big as my house to heat said house.
No termites to worry about, and moisture is no problem. I'd divert my dehumidifier drain to go into the pile to keep it moist. But the gases thing is something else to consider. If it isn't organic I would have no idea what may be entering the air and if I have to run a purifier then I may as well run the furnace since my savings would be nill.
Methane is a by product of aerobic bacteria....micro -beasties...they generate the heat and break down the solids...Methane is explosive.
Compost piles stay outside...google
The genius of Jean Pain...Mother Earth news
Or the Jean Pain method..pdf
The compost powered water heater by Gaelan Brown.... hot water in house compost outside....pain also collected methane to run machines on his farm....
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posted 3 years ago
I raised the level of my greenhouse about 9 inches this fall, so it needed more soil in it. I figured I'd fill up the hole with grass clippings and fall leaves. They were run through the lawnmower so they were the perfect texture for composting. They composted extremely well.
It's a very drafty greenhouse. Keeps the wind out, but leaks like a sieve. I thought that I was going to die every time I went in the greenhouse. The mold, and the slime, and the mycellia, and the must, and the odors, and the gasses were overwhelming. And that was without disturbing the pile. Even with a dust mask on, and the doors wide open, it was unbearable to turn the pile. The heat released was minimal, even though it was a hot pile, there is just too little heat released over too long a time to make any difference. I'd never invite that kind of danger into my house. I had to strip naked on the back porch before entering the house after visiting the greenhouse. It was that bad!
Your mileage may vary. I think compost piles are a disgusting thing to do to organic material. I prefer to just throw refuse towards it's final resting spot and never think about it again. That turning and watching and moving rotting plant matter is for chickens, not primates. But if you like the smell... and don't have family....
I've actually thought about this quite a bit. I was going to look up some more info and make a post about the theory of using compost for heating a small home but never got around to it.
The inspiration for thinking about this is from stories my grandparents told of German house barns. The ground level of the house barn was for animals. As you added more and more clean bedding material through the winter the open animal area slowly built up a layer of manure and straw that could be a couple feet thick or more and would warm up a little as it composted a bit. That helped keep the animals warm and combined with the animals body heat, warmed up the second floor of the building which was the house. (The story was that the housebarn was built into a hill so that the 'house' door faced the hill so it was 'ground level' and you weren't going up and down stairs to get in the house all the time, the barn doors faced away from the hill, so they to were technically ground level as well.) It was also supposed to be really nice that in the middle of a nasty winter you didn't have to go outside to tend to the animals, you just went downstairs. I did a search and I think the "Black Forest House" is close to what was described.
I suspect some are thinking it would stink but I doubt it. My Grandpa had around 25 sheep usually. It wasn't a house barn, just a cement block barn with no heat and no insulation, we never cleaned it out all winter and just kept adding more clean straw all winter. It did smell of sheep a little but nothing unpleasant in the least. It would get a little chilly in the coldest of winter, maybe enough to just barely see your breath. There would be snow outside and us kids would take our coats off to go play upstairs in the loft in the winter. A sweatshirt and a hoodie and you were comfortable.
These are the 2 ideas I had been wondering if they would work. I don't believe either would warm a structure enough on it's own, but like the house barn it could keep it warmer.
1) Heat water in a large outdoor compost pile and then bring that water into the structure to warm up a mass like the mass of a rocket mass heater, or use it through a standard type heating radiator, or run it through floor heating tubes. I'm just not sure how much heat you can pull away from the pile before you kill the process by cooling the pile down to much. I suspect it would help a good deal for such a pile to be insulated against ground contact as well as the elements so you had as little heat loss as possible.
2) When looking at the 10x10 wofati build I was thinking what if you had a concrete room off to each side of the living area. This would make each side wall of the wofati concrete. (Or similar such material) Each concrete room would be wide enough to get a bobcat into it. You could fill each concrete room with material to compost in the late fall, and through each shared wall with the living area warm up that living area. In the spring you used a bobcat to clean it out and then take your compost to the garden or field. I'm not sure how much stirring would be needed but I suspect something like a grain drying bin stirring system would do the job. It could be even better if you could put the concrete room below the structure so the shared heat exchanging portion was the ceiling of the compost room and the floor of the room to heat. Much like the animal area of a house barn.
The heat inside the pile may never make it to the outside of the pile enough to make it all work, I don't know. It would also be a lot of work. Just like stocking up the wood pile for winter you would have to figure out a good mix of compost material and fill up the chambers each fall. Then clean them out each spring.
How about use it to heat the "in floor heating" coils? Similar to how folks use it to make hot water for the shower but instead have the heated water circulate through those in-floor heating systems. ??
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I think heating a house with compost is possible but not easy. Ive heard of Chris's method for barns (piling compost against masonry foundation) and think small homes could do the same thing. It seems the safest way would use tubing with water with a clear separation of home and compost and the moisture and other unhealthy gases associated with decomposition.
While it would be important to make large volumes of compost and use the heat efficiently, the bigger variable to me is the size and efficiency of the home. Tiny homes certainly have the most potential and I imagine they could do pretty well even with relatively low levels of insulation.
For most homes its all about the thermal envelope: airtight, continuously insulated and modest levels of good performing fenestration. With a passive house or net-zero levels of efficiency, it doesnt take nearly as many BTUS to keep the home warm and comfortable.
Ive been thinking of how a home could use compost for space heating without the complications of plumbing and Iam picturing something similar to what Chris describes for the small Wofati. I also picture a home on piers with enough head room below to maintain big compost piles. This is a more dangerous approach and would require meticulous airtight construction for the floor and probably a strong vapor barrier there as well. The only thing that has me wondering is how much to vent down there to keep things safe yet not allow too much heat to escape.
"If you want to save the environment, build a city worth living in." - Wendell Berry
I know a Dutch mushroom farmer that uses a modified Jean pain mound that I hope to implement on my farm. He uses hot compost, chicken manure added to wood chips and sawdust. 300ft pex in compost in an IBC tote. He uses several of these in series, with false bottoms for aeration. Water or glycol is circulated thru the system to radiator coils and panels in his grow rooms. Hope that helps.
posted 3 years ago
Correction: Bruce Fulford investigated heating _greenhouses_ with compost.
Yeah, I was going to say, I volunteered one summer during college at New Alchemy in the 1980s. They were heating a long solargreenhouse with compost bins continuous along the northern side of the greenhouse, forming a sort of 3-foot-high shelf for starting seeds and other warm uses. They weren't trying to run cold water pipes through the compost and pull out huge amounts of heat. I think they did have air pipes that brought a bit of the CO2 rich air up into the greenhouse and oxygenated the compost, but I could be misremembering (I need to read that article! Thanks Brian!) But it's not like it was cranking out huge amounts of heat, it was more like a big warm thing in the north half of the greenhouse, helping everything along.
Compost gets to a high temperature, but I'm not so sure that if you draw that heat out, the compost heap will keep cranking out high temperatures. Well, I could be wrong about that, since the Jean-Pain method claims to do just that.
Works at a residential alternative high school in the Himalayas SECMOL.org . "Back home" is Cape Cod, E Coast USA.
I think that having any compost pile in the home is a bad idea and dangerous with the exception of vermi-composting. Someone above mentioned explosive methane gas in addition to the carbon dioxide that it will produce. Fire is another risk as crazy as it sounds but composting materials can reach combustion temperatures. Here's an extreme example recently in my area, I don't know what a minimum size is before risking combustion:
There should be a way to transfer the heat safely from another location. Otherwise if I were to ever try indoor composting inside for heat it would need to be in some sort of super-duper ventilated box with some fail-safe way to prevent overheating, probably too complex to mess with.
Don't mean to be a downer but its a matter of safety.
No way Scott, that absolutely needs to be pointed out. These piles give off stuff that is not safe to breathe on a regular basis. Any direct heating needs to be done very carefully in terms of air quality.
Here is an indirect method that could be applied to small homes with good thermal envelopes. I think it would be relatively easy to extend this style compost water heater into a radiant floor application. Whats really exciting is that if the "cold" floor is above the warm compost, you could probably get it to thermosiphon with no circulators needed.
"If you want to save the environment, build a city worth living in." - Wendell Berry
Location: Mallorytown Zone 5a
posted 3 years ago
Wow some really great thoughts on what could be done. Just had one while reading. What about building a compost pile under something similar to duct work outdoors, then running the duct though the basement insulated like a RMH so that acts as your thermal bench, then venting outside again. The whole system could be run using a small solar powered fan to get the warm air moving. This way all fumes would be in the ducting, sealed in cob, making it safer for the home, the compost would be outside but close enough to possibly get transfer heat through the basement wall.
I was thinking the exact same thing with a chicken coop. Plus if you build the pile right next door the chickens won't have to travel quite so far to feast from it. Would be perfect for winter conditions.
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