PHYSICAL AND CHEMICAL CHARACTERISTICS OF SELECTED US MUNICIPAL SOLID-WASTE COMPOSTS

Municipal solid waste (MSW) composting has been increasingly recognize d as a promising alternative for solid waste management. Because of th e variation in both geographic origin (thus feed stock) and composting technology, the properties of MSW composts generated in various regio ns are likely to be different. In this study, 10 composts were collect ed from different facilities throughout the USA. Elemental composition and some physical properties were determined. Trace elements and orga nic C were partitioned into water soluble, exchangeable, complexed, or ganically bound, mineral particulate, and residue forms based on seque ntial extraction with H2O, 1 M KCl, 0.1 M Na4P2O7, 0.1 M NaOH, and 4 M HNO3, respectively. Substantial variabilities were observed in both c hemical and physical properties among the MSW composts generated in di fferent facilities. Our results indicate that the trace element conten ts of MSW composts are in general lower than the average trace element s reported for sewage sludges, and below the pollutant concentrations (PC) for sewage sludges regulated by USEPA. The exception is for Pb, w hich was higher in some of the MSW composts than the average Pb conten t in sewage sludges and exceeds the PC. Solid particulate was the domi nant form of Cd, Mn, Cu, and Pb, but the majority of Zn was organicall y complexed. Both solid particulate and residue were dominant forms of compost Cr and Ni. The differences in distribution patterns of trace elements in the MSW composts studied indicate that these elements will vary in their potential mobility and bioavailability in the environme nt.