The issues of municipal solid waste (MSW) disposal are becoming more complex as landfills close and environmental concerns increase. One alternative to continued landfilling or incineration is the development of MSW composting facilities. These facilities process raw waste into MSW compost, which can then be used for agricultural, revegetation, and landscaping purposes. However, if the MSW compost does not have suitable qualities, such as an optimum carbon-to-nitrogen ratio (C/N), or if it contains high levels of heavy metal contaminants, its use for these purposes is questionable. This case considers a dilemma faced by a farmer in southern Minnesota in 1992 who used MSW compost as a soil amendment for his vegetable garden. Besides being associated with nutrient stress to his crop plants, the compost was suspected of containing heavy metals. The case permits students to examine issues associated with environmental contamination by MSW and to make decisions based on agricultural, environmental, economic, food safety, and ethical considerations. This case has been tested in junior and senior high school social studies and science classes, as well as in a univeristy undergraduate environmental science course. A majority (65%) of the high school students rated the case positively, while 75% of the university students evaluated it as good to excellent. S.R. Simmons, Dep. of Agronomy and Plant Genetics, 411 Borlaug Hall, 1991 Buford Circle, Univ. of Minnesota, St. Paul, MN 55108; C. Hassel, M. Reicks, and J. Schramm, Dep. of Food Science and Nutrition, Univ. of Minnesota; and A.H. Duin and E. Lammers, Dep. of Rhetoric, Univ. of Minnesota. Minnesota Agric. Exp. Stn. Journal Series paper no. 20 773. Received 1 Sept. 1993. 'Corresponding author (ssimmons@maroon.tc.umn.edu). Published in J. Nat. Resour. Life Sci. Educ. 23:103-108 (1994). U RECENTLY, landfills were widely regarded as the least expensive and easiest means for disposing of municipal solid waste (MSW). However, existing landfills are closing, and pollution concerns have made new landfill sites difficult to establish. Disposal into landfills is now much more expensive than a decade ago (Halbach, 1992), which makes consideration of alternative disposal strategies feasible. Production and use of MSW compost has received intermittent attention over the past 30 yr (Rosen et al., 1993). Municipal solid waste is defined as waste generated by domestic and industrial sectors in municipalities, excluding sewage sludge (McCalla et al., 1977). However, MSW compost is sometimes produced with the addition of sewage sludge to provide N and to accelerate the composting process. There were 16 MSW composting facilities operating in the USA in 1992; almost all have been constructed since the mid-1980s (Kitwana, 1992). The state of Minnesota was particularly active in MSW composting, with eight facilities operating in 1992. The capacities of these facilities ranged from 9.1 to 226.7 Mg (10-250 tons) of raw waste composted per day. The future of MSW composting depends on the abili1 Teachers who intend to use this case for classroom or extension education purposes may request a copy of the full Case Teaching Note from the corresponding author. Names of individuals and the composting facility in this case have been disguised. Abbreviations: MSW, municipal solid waste; PCA, Pollution Control Agency. J. Nat. Resour. Life Sci. Educ., Vol. 23, no. 2, 1994 • 103 ty to .produce compost that is safe and uniform in quality. In the USA, major uses of MSW compost are in horticulture, landscaping, and revegetation of disturbed soils. For agricultural purposes, MSW quality factors include C/N ratio, odor, pH, soluble salt content, physical properties, nutrient availability, and heavy metal contamination. Elements of concern in MSW are As, Cd, Cr, Cu, Pb, Hg, Ni, and Zn. Municipal solid waste compost can contain these contaminants through the inclusion of plastics, metal objects, pigments, solvents, petroleum products, and other discarded materials. Even with screening and sorting of waste, heavy metal contaminants can still be present in the final compost product. When this occurs, use of the compost might result in contamination of the environment and agricultural produce, and thus pose a threat to human health. The following case was developed to engage students with issues associated with the use of MSW compost involving soil science, crop physiology, and human
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