THE COMPOSTING GREENHOUSE <<<
I think it is a fine idea.
Not that surprising, as they used to heat the cold frames with manure, placed at the bottom, and soil over it.
The hippies did a lot, to bring back the old ways of doing things, much of what we find today comes from their efforts, as does wind and solar energy.
True some worked with it long ago, as I knew a Ben Gilbough, he and Barney Oldfield invented the hot tube, the forerunner of our sparkplugs.
Ben had in the mid 1960’s electric in his house, that was powered by a magneto, attached to a Franklin rear end and it was mounted as part of his windmill.
LOL, as I recall it from over 40 years ago, when he explained it to me, the set up had powered 2 light bulbs of 25 watts for over 50 years.
>>>Not that surprising, as they used to heat the cold frames with manure, placed at the bottom, and soil over it.<<<
Yep, horse manure works really well for it...
I have grown salad fixins all winter by digging a trench and filling it with horse manure, covered with about 6” of soil, then put bales of straw all around that with plastic covering the top and outside of the bales, then a double plastic frame cover on top that we had to open on warmer days. Works great!