‘Mike can headless mice go on to the compost heap?’ my wife calls. Bella our new garden cat has come through her probationary period with flying colours, bringing a mouse to our door almost every day. We congratulate her, but now our compost heap is in need of replacement. I operate a system known as a New Zealand Triple. The system uses three compost bins each approximately a cubic metre and placed in line. You fill the left bin first and, when that’s full, you turn the contents into the second bin. When the first bin is full again, you turn the second into the third, the first into the second and continue filling the first which of course means that your compost get regularly turned. It rots down all the sooner and is taken away for use in the garden from the third bin. All very commendable but when you get busy, you forget to turn them, so the garden waste goes into which ever bin is available. Eventually, as happened to me, you end up with three bins all needing emptying at the same time, particularly relevant now that the bins have come to the end of their useful life.
Compost bins can also harbour vermin. So how do you break down an old compost bin? Over the period of a week, I emptied half a bin at a time, spreading the compost around the garden and when empty, removed the remnants of the bin. This would give any vermin the chance to move on before emptying the next bin. As it happened I had no vermin and the site was soon cleared.
I build my compost bins using pressure treated wood also known as tanalised. The wood is readily available from any of our large farm stores as the elements are all fencing material. Check that the timber is pressure treated; as some wood is sold as ‘treated’ which may mean it has simply been painted with preserving chemicals. Pressure treatment makes sure the preservative is absorbed into the wood. Pressure treated timber will last 20 years; ‘treated’ will last only three. The main supporting uprights of my compost bins are 100mm x100mmx 1800mm fence posts cut lengthwise in half. The sides, back and front are 150mm x 20mmx 1200mm fence boards, cut down to 1000mm in length. The rail system to carry the front boards and the lids are made from 35mm x35mm dahlia stakes. All are fixed together using galvanised nails. Steel or iron nails will last about 10 years, the galvanised will last the life of the pressure treated wood. You will need to build in situ as the final unit is of some considerable weight.
My first attempt at compost bin building was to use pallets but being ‘treated’ they subsequently rotted with their contents. They also create space between their rails for our long-tailed ‘friends’ to take up residence. As for headless mice…. no, they do not go on the compost heap. Ours go in the hedge bottom.
Mike I’Anson February 2017