▪ As more composting facilities come on line across the United States, and a wider spectrum and greater quantity of organic materials are composted, the need to develop a variety of markets for their end products, i.e., compost or mulch, will become ever more critical to the future growth potential for composting and its success. It is often stated that high quality compost will always find a market. However, the economic implications of producing a high quality compost need to be better understood. Publicly and privately operated composting facilities need to compare the costs for building or improving their composting programs to the associated economic returns, i.e., the increased selling price for their product (or, if the product is not sold, the increased avoided cost for what the compost/mulch product is substituted for) and other economic implications. The scarcity of published information on the costs of producing marketable compost at U.S. municipal solid waste composting (MSW) facilities is largely due to the minimal experience in producing and marketing these composts in this country. In order to improve both facility operation and compost quality, most facilities that have operated for more than one year are making modifications, particularly in the type of feedstock, front-end process, composting process, and final compost processing. A summary of such changes is presented for nine U.S. plants, but little information is available on the costs of these modifications, nor their impact on compost quality. Information is also presented about the European experience with MSW composting, emphasizing the importance of producing better quality compost, and the need to fully account for the added costs associated with producing a higher quality compost.