Quality
Composted materials bear little resemblance to the 'peat mix in a bag with added chemicals,' that most people have come to understand as compost. If we want to market our compost to the general public, then we have to ensure that we have the best looking and performing material possible. We have to make sure that the materials are properly composted, regularly monitored and turned and then sieved bagged and presented as attractively as possible.
Quality of compost is not necessarily the first concern of the community composter. We are concerned with stopping that material being wasted and doing something useful with it. If we can plan the system to include a good quality end product, from the beginning, then so much the better.
In order to be sure that our compost is 'sanitised,' meaning that every part of it has heated up properly, we need to turn the heaps at least twice. Ideally the temperature is carefully monitored and the heaps turned at the optimum time. They should be turned until they stop heating up and then left to 'mature.' In practise this is difficult to achieve in largely voluntarily run organisations. We have to do things when we can, and when weather and labour permit. Luckily, compost is benign, we can get away with turning later and it will still re-heat. We are also much more prone to seasonal variation. In the summer we can be inundated with grass cuttings, whereas in the winter it's difficult to get enough green material. However, in the winter we are less likely to be confronted with seeding weeds and roots, and it is easier to stockpile the woody materials without them composting, prior to chipping.
The Devon Rotary Sieve
Designed by Sam Seward
Sieving transforms the compost.
What was an untidy looking jumble, becomes a homogeneous material, which anyone would be happy to use. On a small scale, a hand operated sieve can be made or bought. You can buy small powered screens too, Heeley City Farm in Sheffield bought one second hand for £2,000, it's a serious piece of equipment. You may be luckier and find a second hand machine that you could adapt to be a compost sieve. The Seagull project in Skegness use an old sand and gravel grading machine. Other projects (Lympstone & The Shaw Trust) have adapted old potato riddles.
If you are dealing with larger amounts you could emulate WyeCycle in Kent. Their operations depend on using a tractor with front end loader. They have built a flat screen, which they can mount on a trailer, at 45 degrees. The compost is picked up and poured over it; a few whacks of the screen with a shovel dislodge any blockages. This system has the added advantage of having the material loaded at the same time for bulk sales: or it can be bagged up from the trailer. Using this system it is probably best to have two screens and produce two grades.
