Compost Heated Domestic Hot Water

[Drawbar]

Is anyone on here using the heat generated by composting to heat their domestic hot water?

As a working farm I have access to some serious crop acreage and woodlot and could easily obtain enough compost (haylage and wood chips) to start a compost pile that generated enough heat to at least bring the water temperature up enough so my current propane-powered water heater would not use so much fuel.

At first I thought I could go year-round with this plan, but now am thinking just running it in the summer. This would prevent me from trying to combat Maine's very cold winters and I could recharge it easily by using my lawn clippings and crop ground.

Maybe this venue is not worth doing, but I thought I would ask just the same.

[bob golding]

it might work ,but, you would have to careful how much heat you extracted from the heap. if you took to much you would slow down the composting process. if you put some probes in the heap and  monitored the temperature you would get some idea. i think your ideal temperature for composting is around 95 degrees F.. dont qoute me on that though. if you had 2 heaps you could monitor both of them and when the tempperature dropped too much on one  change over to the other one. you could do this automaticly fairly easially.

cheers

bob golding

[wdyasq]

I think the temperature is a bit higher Bob. Somewhere out on the wild web there are plans for a whole house heater using an insulated compost bin. IIRC it had all the calculations necessary to build one. I do not remember it it was a vaporware or actually built.

Ron

[GaryGary]

Hi,

There is a scheme for using compost to heat water here:

http://www.builditsolar.com/Projects/Sunspace/sunspaces.htm#GreenhouseHeat

Look down the page a ways for "Composting".

The New Alchemy paper is very very good on heat from composting, and the next is a pretty detailed scheme for a combined greenhouse and compost water heating scheme that works.

Gary

[Drawbar]

I did some research on this and it seems as if the temp is actually around 135º. That is if the compost has the right ratio of green and brown compost elements to it. (Think grass clippings and wood chips). I was orginaly planning on heating my shop with compost, (about 300 square feet...well insulated with a 10 foot ceiling) but I am thinking that that might be too high of a goal right now.

As for the BTU's, the basic calculations I read are this...500 pounds of grass clippings and shredded leaves will produce around 4 million BTU's. Of course capturing 100% of that heat would be a challenge, but maybe with a dedicated compost heap built out of concrete and well insulated, you may be able to capture that heat and put it to better use.

I don't have all the answers but I was curious if its worth pursing or not. As I said I got the equipment and the land so I was thinking it might.

Right now I am installing a new propane boiler to my house and was thinking of adding in the fittings and valves I would need to pre-heat my domestic hot water next spring. I am thinking by adding in a circulating pump, tying into my Taco logic controls with a few sensors and basically get the controller to circulate and regulate the hot water coming off my compost heap.

Any thoughts?

[harrie]

Hi drawbar, I think it is deffineatly worth a try, being you have all the equip. and matl. needed. I also think a large open top concrete tank, square or rectangle, and inulated on the outside of the concrete walls with foam, or straw bailes,or even dirt on three sides, leaving a opening in one end for tractor or bobcat access to change compost. I guess than to keep from damaging the pipes, you would have to run the exchanger pipes horzontal in loops between the compost and the concrete walls??? Just some thoughts?? I suppose you would cover the top with a large canvas, or black 6 mill plastic?

[wdyasq]

Or insulate so it won't loose heat...

Ron

[bob golding]

hi ron,

 i guess i must have been thinking of bread,or was it beer?? ;-))

cheers

bob golding

[wdyasq]

Must be bread - Ales like 50-70F for fermentation. The rest do better at lower temperatures. Lambic yeasts make the sour beers and like 90F and higher temperatures.

Ron  

[bob g]

somewhere in my collection of stuff is a link or report of a family of 4 getting all

their domestic hot water off of a 10x10x5ft deep compost pile for 8 or 9 months

they set it up because they needed to compost a large amount of stuff anyway for a green house iirc and decided to give it a try.

it worked for them

i would go for it if i had the space and the compost material

bob g

[Drawbar]

Its kind of funny, everyone on here seems to think it will work, but a few months ago I talked with my State Planning Office that had a booth at a fair (the common ground fair in Unity Maine). Anyway no matter what I said, or how I explained it, the guy was like "it will never work." But just before I left he said "But if it does work for you, let us know so we can tell everyone else." That struck me as being a bit funny.

Its going o take some research, but I spent quite a bit of money on my new propane-powered boiler. Its a very "smart" system in that the boiler is very "smart", the logic controls are very "smart" and the hot water tank is very "smart". I also have room for additional controls so I think I can put in a variable displacement and controllable circulating pump by Taco that is controlled by the domestic hot water tank.

If I do this right, I think I can plumb the hot water from the compost pile and meter the amount of water going into the domestic hot water tank. Between the logic controller and the variable displacement pump, and the Watts flow valves, I should be able to control this hot water with precision...maybe even enough so that any excess heat goes into my radiant floor heating system in the winter. Like I said I got to read up on this though.

[wdyasq]

It WILL work and the research is out there. You only need to find the proper ways to extract the heat and use it.

If it were my project I would find try to sort through all published information before I started.

Ron

[SteveCH]

Some yr. ago, visiting someone in Wales, we toured an old "country manor," one of those giant estates. There was a greenhouse there that had the remnants of a compost-heated system for the greenhouse. At one end of the greenhouse, a large pit was dug in the ground, a bunch of pipes set a couple feet off the ground. They lead into the greenhouse and circulated water through the building. I don't recall how they pumped the water, perhaps a steam engine. But the deal was, they would keep animal/vegetable waste dumped into the pit, keep it turned, and use the heat from composting to heat the water in the pipes.

Now, that part of the British Isles has year-round mild weather, so they don't have to contend with, say 5 degree F. nights. And, those estates had abundant cheap labor to keep the compost bin full, turned, and monitored. They grew citrus fruit in one of the houses.

The compost bin was about half the square footage, in plot view, as the greenhouse, so it was a very substantial operation. But according to the guy giving us the info', the big house had used greens and veggies all year long from their glass houses, all kept warm with compost heat.

[Lumberjack]

I have seen a large scale version that worked well so yes it can be done.

One design you might want to look at before you build the compost bin is the clevis multrum system that is a composting toilet. The method they use may improve your design a touch and be les work....

http://www.clivus.com/describe.htm

[roseboomer]

I've just started to research this myself. I have about 80 acres of woodland, littered with fallen trees that I would like to compost (previous owners did not maintain the woods very well).

I seem to recall that some Scandinavian countries are up on this stuff, at least that's what I think my Dad told me when he researched this topic in England way back in the sixties [he wasn't a hippie, just a tad eccentric].

I do know he built a heavily insulated box in our garden, about 3 feet on each side, into which he would place the lawn clippings. There was a small hole in the side through which he poked a piece of rebar into the middle of the mass. He liked to pull the bar out and show people it was glowing red. Not sure what temp iron glows at, but I think a compost heap will go higher than 160F -- although that may not be all good for the composting process.

I'm torn between starting small as a proof-of concept or making a great big thing right off the bat (if the latter produces excess hot water I know my wife would thank me for a free hot tub).

This page certainly suggests this is all very feasible:

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

[questarthews]

I recently ran across these plans then lost them. In my quest to find them again I ran across this forum and figured I'd post the link here. It may be the plans referred to above.

Anyway, hope they help.

http://mb-soft.com/public3/globalzb.html

[MVIDSMITH]

mother earth news ran an article about this years ago from Jean Pain and Backhome mag also had it in issue 96 sept/oct 2008Biomass Greenhouse Heating

A report on the use of compost to heat a free-standing greenhouse.

http://www.motherearthnews.com/Renewable-Energy/1981-07-01/Compost-Heated-Water.aspx