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.