View Full Version : Compost heat

04-20-2010, 01:57 PM
In an effort to make the greenhouse self sustainable, I have a flurry of things flying through my head for heating the greenhouse in the winter. One of these things is using a compost bin and put a coiled pipe inside filled with water, then do in-floor heat.

The only thing that I'm wondering is how often I would need to turn the compost over. I've been doing some reading, and some people are saying that the only reason you need to turn your pile is to get oxygen in the middle so that it starts the process over, and to get around this, some people have drilled holes in a pvc pipe to get oxygen to the center without the need to turn it over.

How feasible does all this sound? The greenhouse will be roughly 1000 cubic feet on the inside, with limited insulation (obviously). Any other ideas for heating the greenhouse without spending a fortune?

04-20-2010, 02:49 PM
If you got any real heat from it, I think it would stop the composting. The bacteria that make it work need pretty high temperatures to really do anything. Any heat you pull out would just kill the process. The other thing is the gasses given off by the compost. In a close environment like a winter greenhouse, it could be deadly.

That being said, there is no reason to put pipes in it. All the energy released by the compost will leave the pile and go into the air. No reason to put plumbing into it. Energy can't be destroyed, so it will come out of the pile at the same rate it is being released over time. Putting PVC pipes in the middle to prevent turning soulds like a good idea.

04-21-2010, 06:49 AM
I do realize that the greenhouse is a closed system. I should have put in the original post, that this would be designed so that the compost is attached to the outside of the greenhouse, and not internal. There are quite a few case studies on using compost heat to run a radiant heat system, but it also makes sense that if you pull too much heat out of the pile, it will stop generating heat because the cycle will have been killed off.

Maybe I'm trying to find the easy way out, but I figured since I have an abundance of cow manure available to me, I could leverage that for some heat.

04-21-2010, 08:03 AM
If you have fresh cow manure, you should consider making a methane generator and heating with the gas.

04-21-2010, 06:31 PM
dwaller I like the idea of heating with the compost pile .... I've never heard anyone even speculate on this before! It has definitely given me some ideas ;). I've been wondering how I'm going to heat a system of about 800 gallons, 140F sounds like a good heat source! I've got to figure out some heat-conducting "pipe" or "non-toxic hose" (maybe PEX?) to run inside the pile ......... now if I could just collect enough compost .........

04-22-2010, 04:28 AM
Getting enought compost is a problem. And keeping it hot is a bit of an art form. There is a lot of heat in the attic space in houses. Running your air pumps from inside the roof may transfer a little heat if the FT are close. Or move the hot water system into the green house. I wanted a hot house next to the house for heating the house of a day and sharing a little extra heat of a night.

04-22-2010, 08:33 AM
I'm pretty excited about the methane generator idea. The most exciting part is that my wife is fully on board with it (to be honest, she actually suggested that we look into a methane generator originally, since the greenhouse will be located on a farm with 400 head of cattle...).

I'll probably focus on building the greenhouse first, but I do need to figure out what type of heat I'll be utilizing. Forced air would be easy, but I'm guessing it would not be good for the plants, especially in the winter. In-floor is the other option, but I need to figure out what type of water heater to use, and if using methane is acceptable.

The other big one with the methane generator is the storage of the methane. I wonder if it is possible to pressurize it in tanks similar to propane, so that I can store large amounts of it over the summer to be prepared for winter. Lots of stuff to look into.

04-22-2010, 09:05 AM
Forced air is the way to go. In a greenhouse with fish you won't have dry-out issues.

Loads of publications on methane. One source of reprints from the 50's and 60's is here:

07-02-2010, 04:58 AM
Hi floridamary4....welcome... :D

Going by your name....would you be one of my fellow (or lady) Floridians ? There are several of us signed up here... :)

11-03-2010, 04:48 PM
Sorry to bump an old thread, but this subject is one that I have a strong interest in and would possibly like to incorporate into my own AP system.

The idea of using compost for GH heating was well tested back in the 1970's and 80's, and has been used in Europe for decades. The Mother Earth News, Rhodale, and others, ran various types of projects with compost heating, but probably the most successful and extensive GH testing was done by a group calling itself the New Alchemy Institute in Woods Hole Massachusetts. They were able to maintain constant winter growing temps with the use of enclosed and insulated compost chambers along the north wall of their greenhouses as the only source of heat aside from solar gain. Greenhouse air was forced into the center of each of 10 compost bins through perforated pipes, thus avoiding the need for any manual or mechanical mixing. Exhaust from the top of the compost bins was drawn off and forced through perforated pipes laid beneath the compost-rich soil of the grow beds. Soil bacteria then converted ammonia, produced by reaction of nitrogen with water vapor during decomposition, into the usual nitrites and nitrates. Compost heat was thus transfered directly into the soil, maintaining bed temperatures in the 70's F on the coldest winter days, while filtered CO2 was passed up through the soil and made directly available to the plants.

Interestingly, these folks were also early pioneers of greenhouse aquaponics.

Aside from generating heat, compost produces lots of CO2 which increases plant productivity significantly (25% or more.) As I recall, it was found that when unventilated, as is often the case during cold cloudy weather, a lush greenhouse can consume virtually all the available CO2 in an hour or two, thus bringing photosynthesis to a complete halt until more is made available. Many commercial greenhouses heat with natural gas to maintain high CO2 levels and increase crop yields, and some even use compressed CO2 in the summer months. AP and hydroponic systems are especially prone to CO2 loss since there is little or no decomposing organic material in the otherwise soil-less grow beds.

Aside from compost, experiments were also done using chickens housed at one end of a hoop greenhouse and separated from the food growing area by a wall that incorporated straw and sawdust filters to get rid of "chicken dust" which would otherwise settle on the plants. A solar powered forced air system circulated the filtered air from one side to the other. The seasonally enclosed chickens added both heat and CO2 to the system, and their waste was incorporated back into the compost system to apparently accelerate the thermal output. The chickens and eggs also provided an additional food stream, along with the produce and fish.

Manure from cows, rabbits, and goats was also composted using red worms. While not generating much heat, vermacomposting does boost the CO2 levels, and the worms provided a supplemental food source for the fish.

Much of the New Alchemy Institute research was adopted and expanded upon by folks like Anna Eddy who built quite a successful business for herself providing AP salad greens to restaurants in the Cape Cod area. She went on to write a classic book on the subject called "Solviva: How to Grow $500,000 on One Acre and Peace on Earth." (Gotta love that 70's title!) The New Alchemy Institute is now defunct, but some of their scanned original research papers and other publications can still be found online with a little effort and patience.


11-11-2010, 07:11 PM
That is interesting material...thanks I am trying out a compost/worm system this winter
and if I can feed it as it breaks down the heat should be manageable.

A man out in Oregon that designs large flow through worm bins told me that keeping these
elevated worm bins heated in the cold is not the issue he said keeping them cool is the
tricky part. These bins are so active due to the MASS of worm activity and biological activity that they are really a "living machine". I treat my large worm harvest systems that way, they are
a machine that eats fuel and produces a by product. It is all very exciting and as one farmer
friend told me "we don't know anything new, we just know more about it".


11-12-2010, 06:45 AM
Hi Jeff,

Your work with worms is very cool and your insights much appreciated. I'd love to see more pics of your operation.

I'm currently working on a 12' x 20' AP greenhouse design that will have a modest compost and worm area. I've just finished building a rolling compost bin made from two 42" rounds from a wooden cable spool. This sits an a sort of railroad track made from 12 foot 2 x 6's. You just roll the bin from one end of the track to the other to mix and aerate. Just got it loaded up with leaves and garden waste and it works pretty well. When the greenhouse is finished, the track will sit on two rows of cinderblocks stacked two high. This will be filled with horse manure and bedding to feed a population of worms. These, in turn, will help feed the fish.

I'm hoping the compost will add some heat to the greenhouse, or at least act like a sort of thermal mass to help even out the temps. I hadn't thought about the worms themselves generating any heat, but I suppose that makes sense. I've taken pics of the rolling composter, but haven't DL'd them from the camera yet. Will try to post them in the near future.

BTW, I found a link for some of the New Alchemy publications for those who are interested:


Some of the material is scans of the original published journals in PDF format. These files are quite large (150MB) but make for some interesting reading.


11-12-2010, 08:09 PM
Yea Gary I will get some pics..its nothing special but I like to test things out at a low level of construction sometimes before "getting into it" ya know?

I wanted to keep in touch with you on that rolling bin...cool idea. I had a 55 gallon plastic drum once
that rolled on some simple cart wheels and all I had was fresh cut grass,used coffee grounds and some shredded paper and leaves. It reached 160/F in 3 days and I video taped the steam, maybe I can find that and post it up.

I saw an old frig laying on it's side and looked at the coils in back...thought that would be a good
way to run some line in a compost bin and pump water though it "slowly" as not to cool it down. I need ti set up something like that in the winter and see what I can do with it.


11-13-2010, 08:12 AM
LOL. Man after my own heart: Backyard Scientist. Ain't it fun?

You shouldn't have any problem using a heat exchanger in a compost pile. I recall a Mother Earth news article back in the 70's where they simply put an an old galvanized water tank inside a big compost pile and it worked pretty well. Just have to watch the temps in the pile so it doesn't get too low as you draw off the water.

Here are a few pics of the compost roller. These were 42" wide and made from inch and a quarter plywood. The framework is 2 x2's and the outside is 1/4" galvanized hardware cloth. The door is just another strip of hardware cloth with a strip of galvanized sheet metal along the edge. It's attached with 4 loops of wire as a hinge, and two springs from an old desk lamps to hold it shut.

I get the cable spools from a construction company that does work for the telecom industry. I have one set that's 8 feet wide and about 3 inches thick. I've also gotten some 48" plastic ones from the local cable company.


11-13-2010, 07:14 PM
omg I love this...lol 8 feet wide and about 3 inches thick??? :o Wow I want one of those! :lol:
You know I like the screening...very cool and with that amount access I am wondering if I might
try this idea because I get allot of food waste from neighbor. Might try out a small we verison
using some scraps I got. Wife is about tied to be fir with me wheeling contraptions out the
door of pole barn :mrgreen: But it is not my fault I was born this way. :geek:

Some how I need to find a spot for my 4' high 90" diamter round plastic tube that is sitting in her parking spot. I could tell her to park "under it" but I would get a swift kick in the shin from her :D

Did business in another town today with my worm castings...YES!!! My first real retail sales deal
since I started the worm casting harvest system. I am excited because we are not making ends
meet and this might be a HUGE boost for wife and I ;) She is so patient with me but I need to make
it happen and FAST or worms and I are toast! :shock: 8-)

pics coming soon I promise!

11-13-2010, 10:09 PM
congrats & good luck Jeffw

11-13-2010, 10:24 PM

Congrats on that first sale. Here's to many more to follow.

Here's a pic of one of the 8 foot rounds. Takes 4 or 5 people to pick it up. Just about the right size to hold your 90 inch plastic thingie. :lol: The closer one is about 6 feet across, and there is a still assembled plastic spool with a broken edge sitting on top of it.

Here's a pic of one of the 4 foot plastic rounds made into a grow bed, which is sitting upside down on the stand that holds it. The wood is from recycled pallets. This bed will be filled with home-made terra preta made from compost and biochar.

Not to get you in more hot water with your wife, but since you are a great advocate of organic and sustainable practices, try googling terra preta and biochar to learn about this amazing stuff and it's potential for farming and sequestering carbon. Heres a link to get you started: http://www.biochar-international.org/

I've built a pretty nice contraption for making biochar on a small scale. I plan to use a version of this for greenhouse air and water heating. Will post more pics and details if you get interested.



11-14-2010, 09:22 AM
Rfeiller thanks for the comment :)

Gary I bookmarked that site...interesting stuff...I have my head wrapped in books such as "teaming with microbes" and "Harnessing the Earthworm" OLD book but the best one so far in my book...sorta speak :lol:

I live not far from a river, we just had the worst oil spill in my states history, the business is now going
around and offering money to peple to sign then SHUT UP. This oil is NOT like the gulf it is refined
and can be eaten by microbes "such as one radio talk show host likes to boast". I am trying to get people
to try and use other products to feed grass and soil and get off that damn chemical trip! I don't care what
they call it is it NOT natural and that is all they need to know.

After losing so many to cancer in my family and more friends dealing with it now than ever (that never
smoked at that) there is a serious problem in our "food,water and soil". For the kids sake we better make
some changes now and I mean RIGHT now. It might even be too late, kids are eating crap foods plus
they do not understand nature or why it is vital to manage it and take care of it. If this trend continues
we are all losers including those yet to be born. At 53 it matters not to me what politics anyone has
nor what views they have I could care less. What I care about is what I am promoting and teaching
now. I start with worm bins and kids, but it is growing because of interest. 1 day at a time.

Sorry I needed to rant...woke up with fire in my belly :lol:

My camera is at another home so I need to go 60 miles and get it but when I do I will post some pics.

Gary thanks for sharing I am sending that link to a friend that is going into farming 50 acres and
wants to do it the old fashion way, with the Planet's sources :D

peace out

03-04-2011, 09:57 PM
all winter even 5/F my worm bin/compost bin was above 100/F. It is nothing more than a 90 inch diameter plastic ring about 24" high filled with leaves (bagged from riding mower so they are chopped a bit) and now and then 25 gallons of food waste was dumped in and mixed with shovel. Worms hang out at lower levels and the top was steaming all winter. Very cool I could warm my hands easy, methane was present but not horrid. This was in pole barn but NOT closed in real tight so it could vent out to outside easy nuff. Next winter I cam using a COIL system using pipes filled with OLIVE OIL and a on off pump that can transfer the fluids IN to my shop and coil on a well that will be the radiator. Never know until you try right?

11-08-2011, 08:24 AM

Supposedly, the folks at "Growing Power" (www.growingpower.org (http://www.growingpower.org)) have successfully used compost to heat their greenhouses.
They don't offer a lot of information online, but there are workshops they offer. They show a heater being used to heat water for Talapia whoe by-product heat also heats the greenhouse. I'm thinking the compost is used where the cold water species are kept. Check it out for yourselves if interested.


11-09-2011, 04:24 AM
I am very interested in this, however a workshop is out of the question due to distance. While we don't need heat year round down here in TX, a consistant temp through all 12 months would be desirable. I wonder if you can't use the coil method and then run through a thermostat of sorts to kick on only when needed and cycle X amount of gallons or minutes then shut down?

11-09-2011, 07:13 AM
you need a huge compost heap to heat water in any sizable amount.. the amount of water flowing through, if not balanced properly, could cool the compost down to much..a few folks have done some well documented experiments

11-09-2011, 07:42 AM
I am reading the Alchemy links/publications...and there is some valuable stuff here. You should be able to offset the heat loss by shear volume of the pile, or by not flowing water constantly. Interesting stuff. Eye opener to put it mildly.

11-09-2011, 09:27 AM
I am having a hard time wrapping my mind around how earthworms produce heat. Maybe someone can clarify. I understand they can in small amounts simply through the biological process...even trees put off heat just being alive. Ever try a thermal scope in the woods? BUT, in theory then for earthworms to move a 1,000 sq ft greenhouse even a couple of degrees would take a vast amount of worms. Far more than I believe can be contained in a compost pile or worm bin. Does anyone have any experience with this? Also, why does the above reffrenced poultry dust matter? You are washing your food/veggies before eating...just as you wash an egg before cracking it...otherwise you cross contaminate your food with salminila (SP) as the egg comes from the back end of chicken, and feces carry salminila. What am I missing?

11-10-2011, 06:23 AM
I think I am the only one reading this now...but I have news on this topic and I will post it now. So that IF I forget, it's written down now so I can come find it again.

So I have been doing a substantial amount of reading on the New Alchemy guys, and reading notes from some of the 'off paper' crowd...the deal with the above mentioned chickens are this: The purpose of the chicken is two fold, heat and simple protein. But there's concern with the 'chicken dust'. So, the solution is from the available data I have read is rabbits. They don't produce as much dander, dust, etc. Produce #2 in a nice, round pellet that is supposed NOT burn plants and is easily gathered for compost, and can produce more heat compared to a chicken of equal size. The meat is supposed to be so lean, that you can't live off a diet too high in rabbit. Now for all you techies out there, I haven't tested any of this, just what I read. There are also some folks testing dried rabbit pellet as an alternative fuel...like the old buffalo chips from the plains. Definetly not an inscense kind of thing I am sure. But they are burning these in a pellet stove kind of setup. Now for me, that's a bit extreme. I have found though, that my natural gas bill is nearly eliminated, $8/month now...by cutting the water main to house (copper) and replacing with PEX, then running through attic and back down the walls. The heat of TX heats the water prior to hitting the water heater. The Pex is insulated in the attic with 1 1/4 pipe insulation, and still in the heat of summer the water coming out the standard hose bib on the outside is so hot you can't put your hand in it. I don't have a temp on this, as it's so hot I am afraid it will break my therm. Just an interesting observation.