The Nature of Refuse

The authors have presented a unique approach for estimating, on the basis of available data, the change that can be expected in the next 30 years in the physical and chemical nature of municipal refuse. Their approach of categorizing the material into those specific constituents which can individually be reasonably examined for future trends in national consumption is a most appropriate one. The methodology developed to predict future quan­ tity and quality of refuse for any specific locale in the country is summarized in Table 13. These ·equa­ tions require, however, as indicated by the authors, that base data on present quantity and quality be available for that locale. Although the authors have indicated numerous times throughout their paper that their data are strictly national averages (in some cases, state averages), it cannot be emphasized strongly enough that these data should not be promiscuously used as representing any and/or all particular locale (s). It not only' 'may not have any validity", as the authors suggest, it probably does not have any validity. It is believed that the authors' warnings about the usefulness of the specific data they have presented are somewhat stifled by their mention of the "rela­ tively small 95 percent confidence limits" in column 6 of Table 4. These values are artificially low be­ cause they are based on standard deviations of sets of data which are, in themselves, probably means. If the original data are not means, then one could question their value on the basis of their being a likely representative single sample. Seven years of research experience by the dis­ cusser at Purdue University in the development of sampling methodology has indicated that there is litt! e usefulness of "national averages". For example, the combustible portion of municipal refuse was found to vary anywhere from 20 to 75 percent. Such variation is due primarily to the local practice