Taylor 6576 Green Living Compost Thermometer at $12.95, tells you when to add water, when to turn or aerate the pile, when to add green and when to add brown material to keep the bacteria working at an optimal temperature. Bacteria are responsible for breaking down food scraps and other material to create organic compost with the major nutrients your garden needs like nitrogen, phosphorus and potassium in a form readily available to feed your plants. A compost pile kept at the right temperature and with the right combination of carbon (brown) and nitrogen (green) material should smell like soil.