It's alive! Compost is the decomposition of materials and it begins to steam or give off heat when microbes begin breaking organic matter down. The steam is due to the difference between the ambient air temperature and the temperature of the pile. To keep a pile running hot, pay attention to four elements: carbon, nitrogen, water, and air. A hot pile requires enough high-nitrogen materials to get the pile to heat up. Steam indicates the composting process is working well and the microorganisms a