heating with compost?

bev_w(6a)October 22, 2008

Hi all,

My first post to this forum. I'm just about to complete my first greenhouse, built on the cheap with recycled cedar and spruce lumber, a set of "easy up" connectors, and some 6 mil greenhouse plastic. The dimensions are 10x12, and the height is about 8'. I have two upper window vents, one operating with an automatic opener. I have an air intake vent that will be manually operated. The north wall is plywood, painted white.

I plan to heat the structure with water barrels, a small electric heater (if necessary) and a trench full of nice hot compost.

I have access to as much horse manure as I can use, as well as some sunflower seed "tailings" from a small biodiesel operation. The manure and the meal make a powerful and consistently hot compost.

I plan to dig a 2-foot deep trench along the sunward wall of the GH, under the benches. I also read about putting a pipe through the center of the compost and creating a hot air "duct" of sorts.

Does anyone have experience heating a GH with compost? Any advice?

I'm in USDA zone 5 / Canadian zone 6b.

Thanks in advance,


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I'm new to the forum, however, the idea sounds like it would work great for the heat. I might be afraid of how many insects would be in my greenhouse. Let us know how it works, I'm intruiged.

    Bookmark   October 23, 2008 at 2:05PM
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Allow me to welcome both of you to the GH forum. :) I would also like to know if the manure generates enough heat in your zone. It may make it too hot on a sunny winter day though. You'll need good ventilation and a shower after every visit out there.

    Bookmark   October 23, 2008 at 8:04PM
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timf7(Z5 40m w Chicag)

I've been fascinated by this idea for a number of years but until this year haven't done much. With an increasing number of winter markets around Chicago, I want to grow or at least harvest vegetables through the winter. My aim is to use inexpensive materials and only sun power. Here's what we have done so far.

Structure: 70' x 15' single poly hoophouse, steel hoops, no power or heat.
Ino\puts: About every four weeks we receive a large dumpster of horse manure, wood shaving bedding, and urine from a local stable.

Actions so far: About 10 days ago we dug a one-foot-deep trench about 6' wide. along the north wall. We layered in the horse manure, some green materials and a bit of soybean meal to add nitrogen to help keep the mix hot. We only built the pile for about 15' and it started about 3' high up against the plastic. By the second day the center of the pile was about 150 degrees and has maintained this level since, although the pile has slumped nearly a foot, a normal occurrance.

After the first temperature measure we checked to see if the inside of the plastic was warm but it was only slightly warm but we then determined that any heat conducted to the plastic would quickly diffuse into the house so the plastic would not be noticably warm. We think it's working so far but it's darn hard to measure, especially since we haven't started to seal up the house for the winter.

Issue 1. The weight of the compost is pushing pretty hard on the plastic so we're going to put some battens between the inside of the plastic and the steel hoops to take the pressure and then rebuild the pile. We'll extend the pile for the full 70' and halfway across the east and west end walls.

Further thoughts:

1. Is there a more effective way to get heat out of the pile? The hot air pipe duct sounds promising. I've also though of figuring out how to make some kind of aluminum
structure inside the pile to conduct heat to the plastic.

2. It seems that heat will escape from the pile into the ground from the bottom (might be ok if it warms the soil under the house), and into the air around the edges (When I happened to set the digital thermometer on top of the pile, I noticed it read several degrees higher than if it were next to the pile.). If we insulate the pile somehow, can we get more heat into the house?

Things to try: 1. Tape a piece of plastic on the outside along the north wall about 5' high and drape over the pile and seal at ground level. This would keep the rain water out of the pile, insulate the pile a bit, and maybe convect some more of the heat to the plastic.

2. Thoroughly seal the house to keep heat in.
3. Insulate the inside of the north wall with reflective insulation. I know we will get more light and hopefully, more heat.
4. Stretch a white plastic or fabric on the ground on the south side to reflect in more light until we get a good snow cover.
The above changes will keep us busy for a while and should help a lot. Last year with only some reflective insulation on the north wall and row covers on the beds we harvested all winter and observed some growth in onions and carrots during December and January. Now that the weather has cooled, we have begun transplanting lettuce and spinach by thinning some outside beds we planted in September. I'll try to get pictures and move info soon.

Beware: Thinking to much about how to make this work could make for some sleepless nights! ;-)


    Bookmark   October 26, 2008 at 10:00AM
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Hi, I thought this was a neat idea when i heard about it on here a couple of months ago and since then have put a tumbling compost bin in my 6x6x6 greenhouse. It worked pretty well so far with our daytime temps being in the forties my gh is well into the nineties and has even gotten to a hundred and ten. the only problem im experiencing now is that at night when the temp drops to the teens my gh temp goes down because my compost is already almost done so it doesnt heat up much anymore and i dont have alot of stuff available to rev it up with. i insulated my walls with bubble wrap stuff and i have three milk jugs painted black in there to help conserve heat but some of my plants are still showing signs of cold damage.

    Bookmark   October 26, 2008 at 4:28PM
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Responding to Tim,

It sounds like your trench is outside the GH. I'm putting mine inside, under the benches, so the heat will rise to warm the seeding trays. I want a deep trench-- about two feet-- just to keep the compost from slopping around into the center aisle.

I need to devise a way to get the benches out of the way so I can turn the compost easily. Maybe a hinged tabletop that flips up ...

I think there may be insect issues (although I don't have any trouble with my outdoor bins) but perhaps not. This stuff gets really hot and the manure is about a year old, no longer attracting flies.

Your points to ponder sound more like light-gathering than heat storage. Unless you have a way to capture and "slow release" the heat generated during the day, I don't think the addition of reflective materials will make much difference to the night-time temperatures.

My half-baked heat storage ideas include some kind of black-painted "wall-o-water" for the north wall. Think of a those water-filled tubes that you can put around tomato plants-- the same concept.

Riley: That's the trouble with hot fast compost. You have to keep making new batches, and you need a constant supply of feedstock. I hope you can find something locally.


p.s. Can someone recommend a reliable but inexpensive thermometer with a high and low temperature alarm?

    Bookmark   October 26, 2008 at 7:46PM
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Think about it. If it worked well, all commercial greenhouses would use this system. It works in a cold frame for starting plants in early spring time because most cold frames are short, small and the plants are near the heat source. You would have to generate a lot of heat from the compost, manure and store lots of heat in the barrels.

    Bookmark   October 26, 2008 at 11:47PM
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I disagree. Just because commercial greenhouses don't use compost heating doesn't mean they wouldn't-- if, for example, the price of propane or heating oil tripled.

Compost heating worked well enough before the era of cheap energy, and it may be the only viable alternative to heating with carbon-based fuels. I say "may" because there may be developments with heat storage, biomass-based fuels and earth-sheltered building that may come online in time.

I say "well enough" because, in the past, commercial greenhouse operations were not the multi-acre spreads that contemporary industrial agriculture now requires. For a small, non-commercial greenhouse like mine, compost may work very well.

As the Carbon Age comes to an end, I deliberately want to use the old ways, and to learn from someone who has actually done it-- or remembers seeing it done.

- Bev

    Bookmark   October 29, 2008 at 10:47AM
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jbest123(Zone 5 PA)

Years ago, almost all commercial GHs were heated with HM. They all had knee-walls and inside was constructed a bin about 3 X 3Â X length of GH with the outside of the bin being the knee-wall. The top 6" was filled with topsoil and the plants grown there. Along came coal boilers and they converted to steam heat, piped through the floor and the bottom of the planting beds. If you were considering this in a hobby GH, it would be cheap heat and a terrific source of premium compost for the garden. If I were a younger man, that is exactly what I would be doing.


    Bookmark   October 29, 2008 at 4:13PM
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John, thank you so much for your response. That is just the kind of information I was looking for.
- Bev

    Bookmark   October 30, 2008 at 10:40PM
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Bev, I assume you have, but have you seen this website? http://ersson.sustainabilitylane.com/greenhse.htm very creative, inspiring stuff.

    Bookmark   October 31, 2008 at 11:52AM
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A gardener here was severely
BURNED when his compost pile ignited

    Bookmark   November 7, 2008 at 4:27PM
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Im very interested in the this idea also.

I have a homemade 24X15 PVC/Rebar greenhouse with 1 layer 6mil plastic. Im growing cool season greens with solar heat only.

My plan is to keep it really simple. Just create a decent size pile in one corner, add kitchen scraps,manure, whatever i have... when available throughout the winter.

Im not looking for a huge amount of heat output. Im primarily interested in
1) Having a non-frozen pile I can play with throughout the winter.
2) Create a small amount of thermal mass and heat to make the nighttime temps a little higher.

I've read some posts here and elsewhere online about harmful gases accumulating in the greenhouse from composting. Is this something I should be concerned about with the plan I have?

    Bookmark   November 20, 2008 at 8:56PM
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timf7(Z5 40m w Chicag)

bswampy, Check out "Growing Power" urban growers in Milwaukee. I believe Will Allen heats his hoophouses with several compost piles inside a large house. I think your challenge will be getting your small pile to heat up and stay warm. Also, insulation will help as will putting something white on the north wall. Hope you can make it work. Tim

    Bookmark   November 21, 2008 at 6:34AM
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Thanks for the info Tim.

I looked around growing power website and there is a lot of interesting stuff there.

I'm planning a making a pile about 1 - 1.5 cubic yard size and I wont be too worried if the pile cools off. My goal will be "warm" composting I suppose.

Whats holding me back is not knowing how much, if any, concern I should have for harmful gases being released as a byproduct of composting. I'm hoping to keep this as simple as building a pile in one corner and letting it do its thing. Am I going to need any additional ventilation or filtration?

    Bookmark   November 22, 2008 at 9:14PM
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timf7(Z5 40m w Chicag)

bswampy, I think the pile should be slightly moist if you want composting to occur. Here near Chicago it's getting cold and the ground will be frozen soon. I need a continuous supply of compost/potting mix during the winter so I'm making some in my hoophouse. First, I covered my long pile outside next to the north wall of the house with leaves to insulate it from freezing so I can dig into it to get some partially finished compost when I need it. Insulation can help keep the pile going through much of the winter to provide some heat.

With the volume of your pile and the volume of air in your house I believe any gas contration would be minimal.

I assigned part of one bed inside the house as the composting area. I started off with some horse manure and wood shavings and worked it into the soil along with a bit of soybean meal (chicken feed) and alfalfa pellets (rabbit food), the two being high in nitrogen and readily available at most any feed store, and watered it in. I give it a quick mix with a hoe about once a week or so and add anything I have to the mix and keep it moist. Worms love any food you put in and will help the process along and soon you'll have some black, rich, light soil mix. I don't know if any heat will be generated but it would be easy enough to find out if you have a couple of cheap digital thermometers.

Yesterday I lined the north wall with white plastic (100' by 10' Panda Film From: "Usisu, Inc. (HorticultureSource.com Division)" which cost about $90 including freight. I just tucked it in between the poly and the hoops and it looks like it will stay in place with any taping. When I get a chance, I'll slip in some bubble wrap behind it. The sun was out and right away I noticed that the house was a little brighter, and hopefully a little warmer. In the next few days I'll bring in a small water tank for a supply of water (It's cumbersome to get water from the spigot 500' away), lay down some white tarps on the ground along the south side of the house to bounce in more light, and seal up the cracks around the doors. Hopefully, it'll be pretty bright inside and I'm thinking of moving my hammock in there to get a little light therapy! ;-)

Good luck with your project, Tim

    Bookmark   November 24, 2008 at 9:07AM
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Long time lurker here, and first post. Been studying this whole concept for a long time, and experimented with it last year in our 4K square foot greenhouse. There is a bunch of info out there. Check these:

farmshow.com Katherine Brooks
google jean pain
new alchemy institute did alot with this in the 70's
magicsoil.com is a commercial grower that uses compost heat
steve at singing pig over on the new farm site uses compost as well.

Solviva had a pretty simple solution on the excess nitrogen from her chickens that she was blowing into the GH. She used an earthlung which is nothing more than peat moss, which absorbed the excess nitrogen.

Katherine has a book for sale if you want to get more details of what she is doing. Her idea of using a sump pump to move the heated water was the missing link for us. Jean Pains goal of cooking methane gas in his compost heap while at the same time. heating the water is where we are going. I read a while back where some Aussies were running biodiesel instead of water. Don't know how that came out.

Let's try and keep this thread going as we all stumble along. We grow through the winter in upstate NY without any heat source. Last year I was able to raise the growing beds temps by around 5-10 degrees which just wasn't enough. I'm cheating right now using a water heater. I know the compost will heat the water, its the way the whole system fits together is what I'm trying to figure out.

Best hopes

Lucky Dog Farm

    Bookmark   November 25, 2008 at 1:39PM
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I used a compost pile to heat water for an outdoor shower this year that worked very well. The pile was about 3.5 by 3.5 feet big with 500 feet of .5 inch black poly tube coiled within it. The water coming out of this system produced very hot water (almost too hot) and no matter how long I was able to run the shower, I could never deplete the hot water coming out. This setup could easily work with greenhouse heating. You could add more poly tube throughout the soil of the grow beds or through barrels of water and then circulate water through the compost pile.

    Bookmark   December 2, 2008 at 8:55PM
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As one who was far too old and infirm when I fnally got my GH to get into anything labor intensive, I too am reading these posts with interest. However, I still haven't seen any that address the obvious for a GH that will keep warm in winter and cool in summer virtually energy free; a pit.

I agree with the poster who described the way it was done in the old days, but they failed to mention that those old GH's were for the most part sunk into the ground and the further north they were located, the deeper they were dug, to get the floors at least at, and whenever possible- below frost level.

Of all the natural, free and truly endless souces of heat energy available to us, I honestly can't think of any more obvious or unlimited, than the natural thermal properties of the planet.

    Bookmark   December 3, 2008 at 9:20AM
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orchiddude(+7b ALabama)

I like the interest that this topic produces but in all my years no one has come on this site and proved that one can heat a greenhouse to a comforable temp. Like Terri said above, if it was that easy, everyone would be doing it, including me. I wish there was a way, but many people have looked for ideas, but so far, I dont think they have found what they are looking for. There are so many great ideas, but most of them require large areas, or lots of work. I think the bottom line when it comes down to it is, heats not free, you either have to pay for it, or work for it.

The one thing that I have found that works well is to pack your greenhouse full of plants, this creates lots of mass which keeps heats. Then when you heat your greenhouse, you will use less heat. I have my 18x25 ft GH packed out with walking room, and I am able to heat it for less than $300 a year. No work, no fuss. With greenhouses much small than this, folks should be able to heat for less, but its cheaper to heat a full greenhouse with plants than one with mostly empty space. Zones place a large role in how you heat also, my winters are not that bad, but still see low 20s and teens everynow and then.


    Bookmark   December 3, 2008 at 9:00PM
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This is a little too late in responding, I guess, but for what it's worth, for two years in a row I raised 2000+ transplants in a high tunnel using only manure (first year horse manure, second year pig manure). If anyone is still interested I can provide photos and more information. The heat zone is low, but able to keep tomato plants and pepper plants from freezing in single digit weather.

    Bookmark   August 10, 2011 at 5:21PM
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sand_mueller(z 7a, oklahoma)

I used Tulsa zoo manure (and lots of it) in a tight 18'x40' house a number of years ago. As far as I am concerned it is fantastic for sprouting seeds in late winter...that is seed flats laid over the pile. As far as heating an entire greenhouse over a winter; forget it.

    Bookmark   August 14, 2011 at 7:22AM
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Western Kentucky University use a compost system to heat some of their greehouses. They use a system of black plastic pipe through the pile which they pump water through for heat transfer. I'm not sure whether they run the water through heat exchangers or just let it radiate heat from the pipe.

    Bookmark   October 16, 2011 at 12:06AM
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Hi all, I'm new here. For weeks we have been trying to find the best useful information regarding heating a greenhouse with a manure/compost pile. Our setup is vented pipe under the floor with closed pipe through the manure/compost pile on the outside. Piping being fed in and a squirrel fan used to circulate the heat through. We're excited to finish the project...anyone interested in looking at the progress we have made, check out our FB page called "HomePlace"

    Bookmark   February 11, 2012 at 10:20PM
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ralleia(z5 Omaha, NE)

Welcome, PellyRdGirl!

Interesting idea--I will check out the page.

We have a few chickens, and I have been playing around with the idea of doing some kind of combined chicken house and greenhouse (separated by a thin wall of some sort) so that the chickens could help maintain warmth for the greenhouse. Chickens are supposed to put out about 70 watts per bird, if I remember correctly.

There are a number of factors to work out--chickens require ventilation to dissipate fumes, even during the winter, for one.

    Bookmark   February 12, 2012 at 11:12AM
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I know of a person that is keeping their chickens in a hoop house, but is only for protection from the cold weather.
Our wheels are still turning over here regarding our project. Stay tuned to the HomePlace page on FB for updates.

    Bookmark   February 12, 2012 at 12:13PM
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We have a few chickens, and I have been playing around with the idea of doing some kind of combined chicken house and greenhouse (separated by a thin wall of some sort) so that the chickens could help maintain warmth for the greenhouse.


I've heard of folks keeping rabbits in their greenhouses to provide heat.

The chicken idea might work, too. I've seen a guy section off part of his garden shed with chicken wire to serve as the hen house/nesting area for his birds. He simply made a small hole in his back wall to allow the birds access to the yard.

    Bookmark   February 21, 2012 at 3:01PM
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PellyRdGirl- I am really interested in your set up. I cannot seem to find your page on FB... could you put up a link?


    Bookmark   November 23, 2012 at 11:43PM
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Could we use the compost to heat water--similar to permie_josh's use of compost-heated water for his outdoor shower--then circulate the warmed water into a filled, black water barrel. You could probably run a small water pump on solar power. The black water barrel would then be a constant source of warmed water, making it more functional for watering and more functional as the night-time heat sink we want it to be. You could even put the water pump on a timer so it runs only at night, preventing daytime overheating.

Has anyone tried something like this? Does this idea sound crazy? I'm considering trying it in my own greenhouse (I'm very inspired by the compost-warmed shower) so if you have suggestions on improving this plan, please share!

permie_josh, can you give me some more detailed information about how you heated the water? Did you turn the compost pile with the pipe coiled in it? How did you add additional compost to keep the temp up? Does anyone else have experience with this method?

    Bookmark   November 24, 2012 at 8:18PM
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That's the probably the only concept - the one permie josh outlined - that's going to be at all practical. I had a 40 hour course in the design, management and valuation of solar energy systems (25 years ago) and though some things have changed, the basics remain the same.

What permie josh and you have alluded to is an "active" system, with mechanical means to move or store heat. A "passive" system on the other hand would simply rely on the thermal mass of the compost.

The problem comes with turning the pile to keep it active - unless other systems can be designed to aerate the pile. All that tubing tends to get in the way of turning it.

    Bookmark   November 25, 2012 at 9:26PM
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