I need to monitor my compost to keep it from freezing in the winter. Probably not what OP's system is for, given that they are from Australia.
The biological processes produce enough heat to keep the thermally insulated compost bin from freezing easily down to -15C (~5 F). But this requires that there isn't too much finished compost in the bin that won't produce heat any more, so any turn downwards on the thermometer means I'm probably late in emptying the bin. Which happens every year when it gets cold (below -20C/-5F), but can be remedied by a 40W light bulb for 48 hours to heat up and restart the composting.
Another thing that needs to be monitored is humidity, because too humid and the compost goes anaerobic and starts rotting instead of composting. This I "monitor" by smell but this project has some kind of gas composition sensor which could be useful. I don't have issues with this any more as I have practically unlimited supply of wood chips to keep it dry.
But the wood chips bring another problem which is pH levels that may go too low. Here's where I'd really like to have a monitor so I could estimate if I need to do something to adjust the pH.
> But the wood chips bring another problem which is pH levels that may go too low.
Is this something you've measured? I add a lot of wood chips and conifer needles and it's not a problem; the compost ends up between 6 and 7.5 pH (neutral is 7). I also liberally spread woodchips on the paths between the beds and things are fine.
The effects of wood mulch on plants and composts are well understood:
My most-productive compost operation mostly just consisted of just piling stuff up beside my brick shed, which was conveniently near an outside door on my kitchen.
The rest of the process consisted of giving it a bit of a toss with a hoe, a shovel, or a fork if I was outside, bored, and felt like doing that, or giving it a bit of water from the garden hose if it had been very hot and dry. And I did as little of this as possible because taking care of compost, while certainly interesting to me, is just not something I generally enjoy doing.
I really didn't pay much attention to it.
By the time spring came 'round again and I had a use for the stuff, I had plenty of it for the garden.
And this worked very well -- for me, on my scale, in my region, with my needs.
Therefore, I do not need to monitor my compost.
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But not all composting operations are lazy. Sometimes, they are very active. And some operations are large enough (or the available space small enough) that real estate becomes a seriously-limiting factor.
And in these instances, optimizing the process to get higher-quality compost faster can become a very desirable goal.
Optimization of composting is not dissimilar to optimization of any other process, wherein: Having some good data is better than having no data.
I agree with everything else that has been said in this thread!
Just to add on, proper composting helps retain more nutrients in the final product, which is great for soil health, and it also reduces harmful emissions like methane that occur when the process turns anaerobic.
