At what temp does a cold compost become hot?
its an interesting question
I used to make Hot compost, and I do recognise the benefits, but lack of time and idleness are what prevents me nowadays (although this thread has got me to reconsider it).
We have a large garden and a huge amount of material to compost, so at the least I do have opportunity enough. Monty Don's compost heap is like a production line, and I am envious, but the turning looks onerous (on that scale, which is similar to mine), although I'm tempted to acquire a Boy's Toys mechanical digger to do that bit!
When I chuck stuff on the heap, or in the Daleks, it often gets hot - exactly as your describe - but I would still define it as a "cold heap" though as the temperature is not maintained and the heat is localised; because I don't turn it to bring new material and oxygen close to the active bugs, the temperature drops again. The net result is that I don't wind up with nice crumbly compost but something more like soil (and there is probably a high proportion of that in the heap as lots of weeds go in with the roots and soil attached to them)
To kill pathogens and seeds needs both a decent temperature, but also duration of that temperature. The temperature is, usually, not hot enough to kill them instantly, but over a period of time I presume they get denatured, which does the job. (If the temperature gets too hot the composting bugs will be killed, the moulds will then take over, and they are well capable of raising the temperature to the point where the heap catches fire - but those microbes are unsuitable for the best composting process)
It seems to kill everything except chickweed so maybe its not hot enough!
Bindweed is my bugbear. I know I shouldn't put it on the compost heap, but when weeding pretty much everything goes into the barrow.
A possible solution to pernicious weeds, and maybe your chickeed too?, is to drown them in a bucket of water for a couple of weeks and then chuck the lot on the compost heap.
I have a ongoing project of heating compost up in a steel drum which is sat over a fire which is in a metal bust bin with a chimney lid on that works OK and I use it for seed compost
How much do you have to make? Would microwaving it be an alternative? I think if it "burns" over the fire it will be a different material? I have known folk use the burnt soil under a bonfire as "sterilised soil" but all the humus in it has been burnt too, and I wonder if that has robbed some of its potential?