This is a photo of a tractor moving a pile of steaming compost.

Credit: Scot Nelson on Flickr

A compost pile, like this one at a farm in Hawaii, has to be turned over to ensure that oxygen reaches all areas. When organic waste is composted the material gets very hot as soil microbes break it down. Carbon dioxide is released in this process, but that’s much better than when organic waste decomposes without oxygen in a landfill, which releases methane, a much more powerful greenhouse gas.