Municipal solid waste composting: Policy and regulation

Municipal Solid Waste (MSW) composting is a rapidly evolving technology, and as such is subject to shifting policies and changing regulations. Composting is a viable way of recycling organic wastes which comprise a large fraction of the municipal solid waste stream, but there is debate about whether compost inputs should be restricted to source separated "biowastes" or whether centralized processing of mixed solid waste is acceptable. Several additional key policy issues include: how MSW composting fits into an integrated waste management system; compost quality standards and restrictions on compost utilization; facility siting, design, and operation; and regulatory enforcement. As with other policies and regulations, those related to MSW composting are influenced by a combination of science, economics, and philosophy as mediated by the political process. Current MSW compost regulations in North America and Europe provide examples of widely differing policy frameworks and the standards and criteria which result. Risk-based assessments drive compost standards in the United States, while a policy of "no net degradation" of existing soil quality is the basis for standards in parts of Europe and Canada. These different policies result in large differences in the allowable levels of some heavy metals. Unrestricted use of "clean" composts meeting quality standards is generally allowed under all regulations, but restrictions on the use of composts which may contain levels of one or more contaminant that exceed those standards vary. The underlying differences between these frameworks are described, and important uncertainties which research can help resolve are discussed.