Composting uses biological processes to degrade the organic material in biosolids, generating heat to raise temperatures in the compost bed to the pasteurization range. Biosolids composting has been successfully performed in the U.S. since the late 1970s. Biosolids composting involves blending dewatered biosolids with carbonaceous bulking agents, which help increase the porosity of the compost mixture and can aid in supplying carbon and oxygen to microbes, enhancing the degradation process. Several processes can be used in composting, including windrow, static pile and in-vessel.
See, WEF Fact Sheet on Land Application and Composting of Biosolids.