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<p>Evaluate the uses and associated agronomic and environmental benefits for residuals in agricultural and urban systems.</p><p> Specific tasks:</p><p><ol><li>Evaluate the ability of in situ treatment of contaminated soil with residuals to reduce chemical contaminant bioavailability and toxicity. </li><li> Determine the climate change impacts of organic residuals end use options (i.e., C sequestration, N2O emissions).</li><li> Quantify sustainability impacts such as water quality (reduced N impairment) and quantity benefits (increased plant available water, increased drought tolerance) and soil quality improvements associated with a range of organic residuals end uses.</li><li> Explore the potential for waste by-products to be used in urban areas including urban agriculture, storm water infrastructure, green roofs, and in urban green space. (v)Evaluate ecosystem services of degraded urban soils amended with residuals. </li><li> Use tools such as life cycle assessment to understand and compare the impacts of a range of residuals end use/disposal options. </li></ol></p>
Millions of tons of residual by-products, such as urban wastes (biosolids, recycled water, food scraps and other municipal solid waste), agricultural waste (manure) and industrial sludges are produced in the U.S. On average, approximately 50% of biosolids, 98% of food scraps, and 45% of yard trimmings are currently disposed of in landfills or incinerated at substantial cost to the industry and public (King et al., 2011). Reuse of residuals as soil amendments offers the potential to substitute beneficial agronomic and environmental uses for disposal costs. Treated liquid wastes, such as wastewater effluent, recycled water and other non-potable waters, also present opportunities for beneficial reuse in lieu of surface water discharge or expensive treatment. There have been many obstacles to optimized use of residuals. These include a lack of research to optimize residual based product development, conflicting regulations or the absence of regulations on residuals use, and lack of public outreach and communication. There is increasing evidence that land application of a variety of residuals may provide agronomic and environmental benefits that were either not previously well understood and/or that are critical to addressing emerging environmental issues associated with climate change (Brown et al., 2011). The W2170 workgroup propose to continue the investigation of biogeochemical cycling of plant nutrients, the movement of trace element and trace organic contaminants (TOrCs) into the food chain, the potential toxicity of trace elements and TOrCs in residuals to the soil and water ecosystems, and their long-term bioavailability in residual-amended soils to develop additional knowledge to help promote residuals recycling practices that are protective of human health and the environment. To this end, laboratory, greenhouse and field research designed to assess the ability of residuals to reduce contaminant bioavailability in Brownfields, Superfund and other contaminated soils will be conducted. Chemical and biological methods used to evaluate reduction in risk from contaminants to human and ecological receptors will be evaluated. Field biosolids-based N research will be conducted to further refine PAN rates and application timing across climatic regions and soil types to optimize N use efficiency and minimize N loss for agronomic (esp., corn, wheat, hay and forages) crops. These results will provide data for continuing risk assessment required by the USEPA Part 503 Rule for land-application of biosolids as well as for developing regulations for land-based recycling of residuals and reclaimed water. Research will also focus on benefits of reuse including field and watershed scale effects on soil quality, plant drought response, soil carbon sequestration, water quality, greenhouse gas emissions, and climate change impacts associated with soil-based reuse of residuals and reclaimed water. We will also explore the potential for residual based products to be used in urban areas including urban agriculture, restoration, and green storm water infrastructures. W2170 members are conducting research, on both short- and long-term application sites, whose results will enable the development of guidelines for maximizing the beneficial uses of a considerable variety and number of residual by-products.