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[the_madscientist]

Hey, I live in zone 8b, so our winters can get a bit chilly, but we rarely stay below freezing for more than a few weeks each winter.

Have a clear plastic roofed lean-to off the back of my house, that I'm thinking about framing and adding walls to make a little greenhouse.  probably 12'x8'ish.

Now, I think that the greenhouse would still probably get too cold for many plants in the winter.   I've heard of people composting inside a greenhouse to generate a bit of heat.   I'm thinking I could make a 'desk' along the long wall with a compost bin underneath it.  Fill it up with all the dead fall leaves and expired annuals so the compost could cook throughout the winter to provide a bit of extra heat (and CO2?).

Anyone know of composting methods which optimize heat output?   Could I add dilute sugar water or another calorie source to boost microbe activity?  Any methods of preprocessing of compostables to increase bioavailability (fermentation/boiling)?  Good ways of increasing thermal mass inside the structure?

Do you think a cubic yard of composting material could keep a 100-sqft greenhouse warm enough for frost-phobes in my climate through winter? (zone 8b).   Enough to grow Trichocereus, Caapi and passionflower perennially? 

[ONandONandON]

Zone 8b also! i'd say yes go for it. Especially with a clear roof, it was meant to be a greenhouse.
i have lean-to side on house also.. last year i stapled plastic and screening (gives strength to plastic)
it's a tin roof but enough light reaches half the area. Plants love it in there, they're planted in ground..
During winter time, i opened the window, which connects to the house, which let in enough warm air.

i think tricho, caapi, passionflower, be fine without additional heating, but it would help them grow..
Compost heating.. idk, when i looked into it once before, i think it needed a lot, a LOT of compost.
One video i watched on how to heat chicken coop, they piled leaves and dirt almost to top of coop.


Geothermal heating and cooling looks interesting..
- a plastic drain pipe is buried 5' to 8'feet deep,
- maybe about 400ft long, with twists and turns
- fresh air is pumped threw with fan
- air is cooled in summer and heated in the winter

Maybe possible to combine geothermal with compost heating.. but then it wouldn't work for cooling.
Drain pipe located at the bottom of compost pile.. then air is fanned threw to collect compost heat.

Goodluck with that, you got all summer

[the_madscientist]

Cool!  Thanks for your feedback!  I'll probably give it a whirl and see how it goes.

> Maybe possible to combine geothermal with compost heating.. but then it wouldn't work for cooling.
> Drain pipe located at the bottom of compost pile.. then air is fanned threw to collect compost heat.

Check out "Pain Mounds" - basically using compost as a hot-water or air heater.  I'd love to make one of these eventually, but probably a bit too large for my backyard :-P  Project for my someday forest retreat. 

https://permaculturenews.org/2011/12/15/the-jean-pain-way/ (see "Harvesting Heat" section)

[Ian Morris]

French agro-scientist Jean Pain has developed a method that i have always wanted to try.

Essentially he uses compost to heat water that is run from the heart of the compost pile to the flooring of green houses. 

Have a look and let us know how it goes.

https://waldenlabs.com/compost-water-heaters-from-jean-pain/

[kykeion]

Here is another resource worth checking out.  It includes some further research and adaptation of some of Pain's methods.

https://books.google.com/books?id=WqZwAwAAQBAJ&lpg=PP1&pg=PA1#v=onepage&q&f=false