Strategies for Separating Contaminants from Municipal Solid Waste Compost

separation approaches affect organic contaminant levels. Thus, this fact sheet will focus primarily on heavy metal contaminants. Those metals of greatest concern in compost—cadmium, mercury, and lead—can be harmful to animals and humans at relatively low concentrations and tend to accumulate in soil, plants, and animals. For most of these potentially harmful metals, the levels in MSW composts are low relative to levels considered acceptable in sewage sludges (a.k.a. biosolids), i.e., the No Observed Adverse Effect Level (NOAEL) or Alternate Pollutant Limit (APL) allowed for unrestricted distribution by the US EPA (Fact Sheet 6). While MSW composts can usually meet these proposed sludge regulatory limits for most metals—with the significant exception of lead—there is an increasing interest in achieving even lower levels. Many regulators and policy makers, concerned that the risk assessment methodologies used to develop standards such as NOAEL may be based on insufficient data, are taking a more conservative approach (Fact Sheets 5 and 6). Several European countries and Canadian provinces have proposed or enacted extremely strict standards, which are sometimes based on background levels of these elements in the soil (Fact Sheet 6). The range of regulatory STRATEGIES FOR SEPARATING CONTAMINANTS FROM MUNICIPAL SOLID WASTE COMPOST