On site Composting of Restaurant Organic Waste Economic Ecological and Social Costs and Benefits Marisa Mitchell Abstract On site composting is examined as an alternative method of organic waste disposal in San Francisco Bay Area restaurants Since 74 of an average restaurant s waste stream is compostable material composting and reuse of organic material would redirect a significant portion of the waste stream from landfills Economic ecological and social costs and benefits of three methods of organic waste disposal are compared landfilling off site composting and onsite composting A waste characterization of one large Emeryville restaurant is performed to determine the mass of the organic waste generated An economic analysis of the three methods of organic waste disposal is made for the specifications of this particular restaurant and ecological and social considerations are proposed for each method Two commercially available composting technologies are compared For the more appropriate technology present discounted value and payback period of the hypothetical investment are calculated based on the current expenditures for landfilling service An ecosystem modeling method is performed as a means to visually represent ecological sustainability A life cycle approach is taken to determine the ecological impacts of the use of agricultural soil conditioners and fertilizers impacts that would be curbed to the extent that restaurant compost is used in their place Social costs and benefits are compared based on the goal of economic ecological and social sustainability as a follow up to the scientific results It is found that on site composting is ecologically socially and economically more valuable than landfilling or off site composting although significant management constraints exist at this point in time when a composting infrastructure is not yet in place It is also found that a significant market exists for a middleman firm that would incur the management responsibilities of on site composting and benefit from the sale of restaurant compost It is recommended that local governments exploit this market Introduction Currently the US commercial sector generates 24 6 million tons of food scraps and soiled unrecyclable paper and cardboard annually United States Environmental Protection Agency EPA 1999 In restaurants organic materials make up an average of 74 percent of the total waste stream EPA 1999 Composting redirects organic waste from landfills and transforms the waste into a product useful in landscaping gardening maintaining the structure and fertility of agricultural land slope stabilization and even brownfield remediation The increasing sophistication of the available composting technology combined with the passage of AB 939 which mandates a 50 waste stream reduction goal for the state of California by the year 2000 have exposed widely used landfilling as a disposal method wasteful of both space and a potential resource An anticipated rise in landfilling fees may lead businesses to seek alternative methods of food waste disposal These combined factors have created an impetus for research on the relative economic ecological and social costs and revenues of organic waste composting in the Bay Area Composting is a biological process in which microbes metabolize readily degradable organic matter into nutrient rich humus a structural component of soil 1 Specific criteria must be met for composting to be successful and meeting these criteria is especially important for large scale industrial composting operations Technology is currently available to allow low maintenance pest and odor controlled on site composting of organic residuals at restaurants Organic residuals are plant and animal derived and include pre consumer vegetable scraps seeds all animal product including bones post consumer food waste paper products including waxed cardboard and wood including treated wood Brandt 1996 The addition of compost to agricultural land and urban landscaping areas provides many associated ecological benefits including reduced dependence on chemical fertilizers and reduced pollution by accumulation in landfills Composted food waste is currently classified by the EPA as Class A material rendering its land application unregulated Miller and Miller 2000 1 Microbial populations and species diversity change dramatically throughout the phases of the composting process Initially mesophilic bacterial and fungal activity cause the temperature of the organic matter to rise into the thermophilic range 50 C Thermophilic microbes especially actinomycetes maintain thermophilic conditions within the organic matter if provided with sufficient oxygen This requirement is met through aeration of the organic material Mesophylic microbes are present during the final curing stage at lower temperatures The heat generated during the thermophilic phase of composting is intense enough to kill pathogens and seeds EPA 1998 Food waste has been used as a soil amenity as far back as the middle ages in Europe and evidence in Amazonia suggests that food processing wastes were added to soils around the same time Miller and Miller 2000 By 1940 inexpensive inorganic fertilizers had become widely available and used due to their short term results on crop yields but more recent evidence of adverse ecological effects such as contamination of water supplies due to inorganic fertilizer application has led to a renewed interest in organic fertilizers Various methods of organic residuals management should therefore be evaluated based on three categories economic value ecological value and social value Revealing categorized benefits and deficits of various methods allows for an in depth multilayered comparison of those methods Economic costs and revenues are equal to the current actual costs and revenues of managing organic residuals in various existing or hypothetical ways Ecological costs and revenues can be determined through the valuation of environmental externalities with regards to energy consumption materials cycling and pollution generated and avoided Social costs and revenues can be determined through an analysis of the long and short term value inherent in initiating re use behaviors vs the maintenance of waste behaviors Study Focus It is hypothesized that on site composting is more ecologically and socially valuable and less economically valuable than landfilling organic waste in the San Francisco Bay Area This study
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