[RebelRidin]

Sounds like you have it figured out. I suspect you are spot on about the sawdust. I know the same thing will happen if too much water accumulates/the manure is too wet. My father would muck out the stall of one of my great uncle's milk cows. Bedding was straw and a little waste hay. That stuff was probably a third straw and was active and producing heat when it went in.

I once set up a cold frame with a heater cable. I only got to use it for a few years before I moved but it worked pretty well.

??? Are you feeling daring ??? You could grow out one of those volunteer tomatoes to see what you get?