This gives me an idea. We have a very large compost pile from mucking out various horse stalls and pens. It's mainly composed of urine-soaked woodchips and mostly broken-down horse manure. There's also some dirt in there as well. As an experiment this summer, I tried growing potatoes and carrots in it. Potatoes did extremely well, the carrots not so much (but I attribute that to poor watering).
It would be interesting to monitor the temperature to see how active it still is, since I can tell that it's not completely broken down yet. I actually have an ESP8266-based temperature sensor around here that I was using to track ambient temp for another fermentation project.
Now I'm thinking of encapsulating its thermistor and putting the 8266 in an IP67 enclosure along with a solar cell and just planting the whole lot on top of the compost pile. It already serves a web page on a .local domain so there would be minimal work required on my part.
I might actually get to that this weekend!
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