Summary: The volume of garbage and sewage sludge being generated is increasing sharply while landfills, open dumps, incinerators, and ocean dumping are becoming exhausted. Codisposal is an alternative that is both economically and technologically feasible. The two basic approaches to codisposal use garbage as fuel for sludge drying or burning, with the objective of using the heat from burning garbage to dry the sludge to its self-burning point by means of hot flue gas or steam. When dry, the sludge can be burned along with the garbage to power wastewater treatment plants. Although Europe has several plants in operation, the United States has only a few, perhaps because of a lack of detailed technological and operating data. The Environmental Protection Agency (EPA) and the Department of Energy are studying foreign facilities to acquire information. Most codisposal facilities attempted here were made with incompatible equipment and were abandoned in the mid-1970's as expensive and ineffective. Abundant land disposal alternatives reduced the incentive to invest in expensive equipment, but interest is reviving and five projects are now under construction or in the planning stage. Most cost information is merely estimates or projections, but codisposal appears to be economically feasible. The availability of Federal construction funds will be influential, but existing programs do not provide for garbage treatment. Several laws seem to offer EPA a mandate for initiating such activity using a prorated funding formula. The potential environmental risks of thermal codisposal include air emissions and groundwater contamination, but the problems appear manageable. Also, the separation of certain garbage items and pretreatment of industrial wastewater may reduce environmental impacts. A formidable barrier to codisposal is the division of garbage and sludge disposal jurisdiction between different local authorities in some areas. The EPA Administrator should require States and communities to consider codisposal alternatives, require development and dissemination of cost data in the evaluation of future projects, establish a construction grants funding policy, and undertake research to identify and analyze the health and environmental impacts of thermal codisposal.
