The Big Question
How can I make compost faster?
AIn a well-designed standard compost heap or bin, it should be possible to make a reasonable quantity of compost in as little as nine months, but not much faster. Much faster composting – around 90 days – is possible in wormeries and ‘hot’ composting bins, but both of these methods will produce very small quantities in that time frame, and they require careful management and monitoring to ensure that the contents don’t turn to slurry. Standard composting, however, is a reliable and steady process. By understanding the process, you can turn all your garden and kitchen waste, as well as certain papers and cardboard, into rich, moisture-retentive compost in the shortest possible time. The basic form of decomposition is the aerobic method – which relies on plentiful air – and results from the simultaneous interaction of carbon and nitrogen. In plants, carbon is found in cellulose and lignin in wood, while nitrogen is in the soft, leafy tissues. For efficient decomposition you need a ratio of around 2:1 of carbon-rich and nitrogen-rich materials (see panel opposite). As well as this chemical interaction, composting needs fungi, bacteria and soil organisms, including worms. They all use the materials as a food source in their life cycles and the rate at which they operate depends primarily on temperature. As a basic rule, warm weather hastens the composting process.
Importance of heap size
A well-built, established heap will generate heat as the materials start to break down, and if that heat is retained, the speed of decomposition will be maintained at the centre, even in cold weather. The minimum size for a compost heap, to keep it warm enough for efficient decomposition, is 1m x 1m x 1m. In winter, heat can be held in the heap’s edges by covering the top with a piece of old carpet and insulating the sides with polystyrene. Pre-formed compost bins are sometimes smaller, so temperatures are lower and decomposition can be slower. As mentioned earlier, air is vital for standard composting, so avoid obstructing ventilation holes in ready-made bins. Compost ingredients shouldn’t be too tightly packed in either, so don’t add deep layers of grass clippings that will obstruct air movement. By mixing different types of ingredients together you keep the structure of the heap open and well aerated. Rapid decomposition also relies on moisture. Leafy, green materials provide some, but natural rainfall and humidity in the air helps to maintain moisture. Add water to covered bins in hot, dry weather to prevent contents from drying out. And lastly, it is important not only to stir the upper layers of your compost every two weeks to ensure it’s well mixed and will start to rot, but you should also mix the whole stack a couple of times during the year. This brings moist, composted material towards the surface and buries fresher matter, so the speed of decomposition is increased and more even.