The role of organic residuals in urban agriculture

Abstract

Urban agriculture offers the opportunity to restore soil treatment of wastes as an urban ecosystem service. While direct deposition and treatment of wastes on soil may not be feasible, using soils as a receiving medium for fully or partially treated wastes is. Residuals pertinent to urban agriculture include recycled water, yard wastes, food scraps, and municipal biosolids, the solid residual from wastewater treatment. Benefits associated with use of these materials on urban lands cover multiple categories. Resource conservation, greenhouse gas mitigation, improved soil tilth, higher net primary productivity, reduced infrastructure costs, and increased environmental literacy and awareness are some of the benefits (see soils section). This section will provide a basic background on waste treatment and describe types of organic residuals available in all urban areas. Composting is the most common means to stabilize organic wastes to make them suitable for use on urban soils. Composting can occur in a decentralized manner or as a municipal alternative to landfilling. A case study describes how food scraps were diverted from landfills to composting in Seattle. This is presented both from a political perspective and from the composter’s perspective. Small scale decentralized composting is also discussed. A final section will compare the environmental and economic costs of different waste treatment options.