How Does Composting Work?

A compost heap needs a mix of nitrogen-rich 'greens' such as food scraps and grass and carbon-rich 'browns' such as dry leaves and cardboard. Microbes break down this material, and their activity can heat the heap to 55 to 70 degrees Celsius, which kills many weed seeds and pathogens. Turning the pile adds oxygen so aerobic microbes can work efficiently and bad smells are reduced. Worms, beetles and fungi help break material into smaller pieces. After several weeks to months, the result is dark, crumbly humus that improves soil structure.