Co-processing municipal solid waste (MSW) and sewage sludge in cement kilns can both reduce the cement industry's growing fossil fuel use and carbon dioxide (CO2) emissions and help address the increasing need for safe and environmentally sensitive municipal waste treatment and disposal.
The cement industry accounts for approximately 5 percent of current anthropogenic CO2 emissions worldwide. Given increasing cement demand and production, the industry's absolute energy use and CO2 emissions will continue to grow. Cement kilns typically burn fossil fuels, which are non-renewable and being depleted rapidly. Treating wastes in cement kilns, known as co-processing, can reduce the industry's reliance on fossil fuels and decrease associated CO2 emissions. The ashes from waste co-processing will be integrated into the clinker which can result in saving the virgin raw materials. In addition, treating wastes in cement production can help alleviate the problems associated with the increase in waste generation around the world, especially in developing countries experiencing rapid urbanization. Municipalities and governments in many urban areas, especially those with underdeveloped waste management systems,face growing difficulties disposing of MSW and sewage sludge in a manner that protects human and environmental health.
The high temperatures and sufficiently long residence time in cement kilns and other characteristics of cement production make co-processing of waste materials a viable strategy. Wastes have been co-processed in cement kilns for more than 20 years, and this practice is prevalent in some developed countries such as the United States and Japan, as well as in a number of countries in the European Union.Many developing countries such as China and nations in Southeast Asia are initiating programs to promote co-processing of wastes in the cement industry. Regulations, standards, and the technical infrastructure in these developing countries are less mature than in countries that have a long experience with co-processing waste in the cement industry.
The purpose of this report is to describe international best practices for pre-processing and co-processing of MSW and sewage sludge in cement plants, for the benefit of countries that wish to develop co-processing capacity. The report is divided into three main sections. Section 2 describes the fundamentals of co-processing, Section 3 describes exemplary international regulatory and institutional frameworks for co-processing, and Section 4 describes international best practices related to the technological aspects of co-processing.