# Heating water from compost



## SolarGary (Sep 8, 2005)

Hi,
I think that someone asked about heating water using the heat from a compost pile a while back. I just ran across this story:

http://ersson.sustainabilitylane.com/greenhse.htm

His scheme gives provides both heated water from compost, and greenhouse space -- all for not a lot of money. Seems like a pretty good idea?

Gary


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## MELOC (Sep 26, 2005)

i like it. i guess you could double the volume of hot water by doubling the pipe. i would like to try this idea, or the mother earth news compost pile heater, tied in with a hot water heater and thermosyphon circulation.


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## moonwolf (Sep 20, 2004)

considering heat from compost that can get 165 is pretty close to that coming from an outside furnace buring wood. sounds like a great idea to try. 
I used in a small greenhouse with some baseboard heaters that ciruculated water from a connection to the nearby wood furnace. This was in early April here when it's often still winter like in the northland.


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## MELOC (Sep 26, 2005)

my only concern would be ventilation and safety. i doubt there are too many air tight greenhouses, but too much co2 indoors could be deadly. having plants would offset that i suppose, perhaps even nourish them.


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## Triffin (Apr 20, 2005)

It would be worth knowing why, after all the effort
to set this up; he only pursued this approach for
18 months and then dismantled it .. couldn't have 
worked very well for the effort involved or he'd still
be utilizing the technique ..

Triff ..


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## SolarGary (Sep 8, 2005)

Triffin said:


> It would be worth knowing why, after all the effort
> to set this up; he only pursued this approach for
> 18 months and then dismantled it .. couldn't have
> worked very well for the effort involved or he'd still
> ...


Hi,
I wondered about that also, and sent the author a note asking about that and a couple other questions. I'll let you know what the answer is.

Gary


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## WisJim (Jan 14, 2004)

After 18 months the bales were probably well on their way to becoming part of the compost instead of walls, and he said that they replenished the compost a number of times. Also, I would suspect that 18 months may have been the useful life of the plastic covering used.


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## SolarGary (Sep 8, 2005)

Originally Posted by Triffin
It would be worth knowing why, after all the effort
to set this up; he only pursued this approach for
18 months and then dismantled it .. couldn't have
worked very well for the effort involved or he'd still
be utilizing the technique ..

Triff ..




SolarGary said:


> Hi,
> I wondered about that also, and sent the author a note asking about that and a couple other questions. I'll let you know what the answer is.
> 
> Gary



I got a note back from the author.
He said that the reason they decided not to continue with the project after 18 months was that it took up to much of their yard space -- their home is on a city lot.
He also mentioned that handling all the compost was quite a bit of work.

He also mentioned that CO2 levels and moisture levels were high in the greenhouse because of the compost, but that the plants tolerated this OK.

Gary


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## Triffin (Apr 20, 2005)

Thanks, Gary ..

Triff ..


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## MELOC (Sep 26, 2005)

i have been thinking, and was reminded by another thread, of the fire danger of composting materials. well, my knowledge of such is limited, but being around horses and hay all my life, i know hay is a fire hazard if put away wet.

at what point does a compost pile become dangerous?


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## mustard (Aug 29, 2006)

Meloc, I asked that same question about a different project, and the response I got was that "straw" bales don't have the same stored energy that "hay" bales do, and therefore are not likely to self-combust....I guess the carbon that makes hay a good feed also makes it more likely to go up in smoke...

M


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## MELOC (Sep 26, 2005)

i have a nice little booklet on composting and i will actually read it sometime, lol. i guess my question is directed more toward the mother earth composting experiments. i can provide those links if you want me to. i found that idea very interesting.

they used a combination of various ingredients. x amount of brown and x amount of "green" compostibles. the right balance of ingredients were to make for optimal heat generation balanced with longevity of the heap.

i probably would not be able to obtain shreaded wood like some experiments used. i have ample manure, green plant material, small twigs to larger branches...basically any size i wish. i also have access to old hay. there is also a sawmill down the street where i could purchase landscaping mulch and possibly sawdust.

i wish to try the compost water heater idea as soon as i obtain a second water heater or storage tank. (the budget is extremely low) i don't want to build it too close to the house and create a potential fire hazard. i don't want to make it too far away, or i lose heat in the pipe and the expense of the pipe increases. i want to put it as close as safety allows.


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## MELOC (Sep 26, 2005)

opps...double dribble


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## SolarGary (Sep 8, 2005)

Hi Meloc,


Don't know if you have run across this one yet. Its a study done by the New Alchemy Institute in 1986 on heating with compost. 
http://www.vsb.cape.com/~nature/greencenter/pdf/compost.pdf

They tried several different types of compost material, and recorded how well each did on producing heat, and how long it lasted. 
They used some forced air cirulation through the compost so that they did not have to turn the compost during its life. 

Lots of detail.

You mentioned a 2nd hot water storage tank. I wonder if you used a pipe coil with enough volume buried in the compost, whether it migh act as a storage tank?
A 300 ft coil of 1.5 inch diameter poly pipe would hold 28 gallons of preheated water. 
Gary


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## MELOC (Sep 26, 2005)

thanks for the link to that awesome pdf !!! it gives great detail of many aspects of the process. i truly wish i had studied horticulture as i intend to someday begin using a greenhouse and perhaps make a business of it. totally awesome pdf ! i would be interested in reading the results of further research.

concerning my more immediate compost heating...

my thoughts were to start a bit smaller than the mother earth heater. my desire was to thermosyphon into a hot water tank in my house and resupply the tank with my current indoor plumbing. i was going to try using only 100-200 feet of 1 inch pipe.

i was concerned about safety. i don't think it poses as big a threat as i thought it might. i have never encountered anything concerning fire danger in any composting article i have read.

thanks again!


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## dcross (Aug 12, 2005)

<<I guess the carbon that makes hay a good feed also makes it more likely to go up in smoke...>>


It's the nitrogen/protein in hay that makes it dangerous when wet. When making compost you shoot for 30:1 carbon:nitrogen, decent hay is just about right, that's why it heats when wet. Straw has little, if any, nitrogen, so it usually won't heat by itself no matter how wet it gets.


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