Compost Heat for Buildings/Greenhouse

I love the idea of heating with compost and I'm glad to see more study and experimentation in the area. There seem to be plenty of articles from the 70s and 80s talking about research in the area, but the interest seemed to die off until recently.


Have you heard of anyone using compost heat for egg incubation?

It's been bouncing around in my head, the idea of thermosyphoning the heat out of a pile and into some sort of insulated box filled with eggs. An electricity free way to hatch a bunch of chicks, or even to warm the chicks for the first few weeks of their lives. I imagine it would provide a nice even heat, but I wonder if it would provide a stable enough temperature for the 3 weeks needed for the eggs to hatch.

I think that's a valid idea. Compost needs to be treated as a big, somewhat unpredictable energy source. To use that big ball of heat (heat reservoir), a tempering valve and circulation pump would keep those eggs consistently in the right temp band....but then we're talking electricity. A little solar panel might be just enough to run a circulation pump.

Great idea!

Build it, then stick it on http://farmhack.net/tools

I think it would be better for keeping them warm after hatching rather than for the incubation as even relatively small variations in temperature can cause the hatch to fail.

The instability is my biggest fear. I imagine you're right, Katy.

Perhaps if it sat on a rather large heat sink. An insulated water tank, or something that could serve a double function of heating a greenhouse or animal bedding area as well as keep a little box stable. I won't let it sit on my idea books for too long. In a few years I'm gonna try this one out and see what I can shake up.

In your experience, Grant, how much efficiency of heat capture does a circulation pump provide? Is it more for efficiently moving the heat or does it do much for overall heat gain? I'd imagine that the pumps more quickly introducing ground temperature water would cool and slow down the pile, so might that extend the pile's life.

Matthew Brittain wrote:The instability is my biggest fear. I imagine you're right, Katy.

Perhaps if it sat on a rather large heat sink. An insulated water tank, or something that could serve a double function of heating a greenhouse or animal bedding area as well as keep a little box stable. I won't let it sit on my idea books for too long. In a few years I'm gonna try this one out and see what I can shake up.

In your experience, Grant, how much efficiency of heat capture does a circulation pump provide? Is it more for efficiently moving the heat or does it do much for overall heat gain? I'd imagine that the pumps more quickly introducing ground temperature water would cool and slow down the pile, so might that extend the pile's life.

Most Jean Pain-style compost mounds can output 140ºF+ water with regularity. A 300-500ft coil of 3/4 or 1" black poly is usually sufficient as a heat exchanger. The more flow (throughput) you require, the bigger the pile/longer the heat exchange pipe necessary. A tempering valve can act as a "temp regulator" on the output side by selectively throttling how much cold water is introduced to maintain a consistent output temp (say 118ºF, something that won't burn).

A circulation pump would only be necessary in a closed-ish loop system with a primary purpose of heating space. You could use a similar tempering setup, but would need two storage tanks to draw from (one hot in compost pile/one outdoors in cool non-biotic environment)

I lived in a home with hot water radiators for years and had the natural gas boiler plumbed in tandem with a biomass (wood pellet) boiler. Systems like this would be easy to add alternative heat sources like compost or wood in a SHTF scenario.

Here's a plumbing diagram for wood-source hot water heating for practical use in a homestead. We'll be talking about these concepts IN DEPTH at the upcoming Advanced Farm & Homestead Design Workshop over Memorial Day weekend May 22-26th in Iowa City.

We salvaged a small wood fired boiler from an old home once and now it runs the in-floor heat we put in our camp; might have been the best find we ever made.

Heating water to heat mass to heat people has worked so much better than heating air to heat people. Hard to believe we've moved so far away from wood heated water in most homes. The prospect of heating a thermal flywheel of a floor, providing domestic hot water and ending up with fresh compost is something we really need to implement.