Last year I took part in a trial of the SoilFixer Super Composter, which involved filling their hot-bin composter with compostable materials and then recording the temperatures that the mix reached, along with any observations about the speed of composting and the quality of the finished product.
The last time I wrote about the trial, in October last year, I’d just re-filled the bin and was planning to see what happened over the winter. What with one thing and another I confess I rather took my eye off the ball, the occasional glance at the thermometer aside, until last week when I realised that it was past time to turn the compost heaps and re-fill the Super Composter for another round.
I started by checking on the contents of the bin. Post-winter, the levels of plant matter in the bin had dropped by a good 75% or so, and what was left was the usual mix of good, usable compost and larger chunks of woody material that hadn’t broken down yet:
After sieving the mix I ended up with a 60-litre compost bag full of the good stuff, which looked something like this:
The woody chunks were chucked onto the compost heap, joining everything from the half-composted bulk of last autumn’s cleared bean, squash and sweetcorn plants to this year’s fresh rhubarb leaves and jostaberry trimmings:
Once the bin was empty I proceeded to fill it back up with the assorted contents of the heap, plus some freshly-chopped comfrey plants (a couple of dozen or so, which is only a fraction of our stock) in green/brownish layers of compost lasagne, with the last of my stock of Soilfixer’s biochar-based compost activator sprinkled in by way of seasoning.
Earlier today (three days later) I checked the temperature of the mix and saw that it had risen from an ambient 13oC when the bin was loaded, to an impressive 50oC:
This is 8oC higher than the temperature that the bin reached during any of the rounds of the trial last year, which could very well be down to the changes to the configuration of the aeration piping that Tony at Soil Fixer asked me to make last Autumn. Still not quite the theoretical maximum of 60oC, but as Tony has said all along, I’d probably need to shred the compostables to maximise the surface area of the material in the bin to achieve that sort of result.
My plan for the next few weeks is to keep topping the bin up as the level drops, making sure there’s a good mix of greens and browns going in. All being well, I should rattle through the rest of the compost heap, plus any fresh material (more rhubarb leaves, mainly) in a couple of months, and have plenty of good, usable compost to mulching with in the Autumn.
Quick Update 29.05.20
Today’s temperature checks:
Air temperature: 24oC
Super Composter: 52oC
Plastic bin of ‘finished’ compost: 26oC
Compost heap (shaded at time of checking): 20oC