Local Biosolids Compost: Agricultural Use, Fate of Antibiotics, and Community Engagement
Youngquist, Caitlin Price
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We investigated the agricultural use of locally produced biosolids compost, the fate of the antibiotic ciprofloxacin during the composting process, community perceptions about biosolids, and sociological factors of community involvement in waste management research and decision-making. Two biological assays were used to determine if the antibiotic ciprofloxacin selects for and amplifies ciprofloxacin-resistant bacteria during composting. A third biological assay measured the capacity of compost to adsorb ciprofloxacin from solution. Our results show that the ciprofloxacin had no selective effect on resistant populations of bacteria during composting and that the compost was capable of adsorbing and effectively neutralizing this antibiotic. A two-year field trial was conducted to evaluate the potential of biosolids compost as a high-carbon soil amendment in local agriculture. Potatoes and small grains were grown with biosolids compost and/or synthetic fertilizer and effects on crop yield, soil fertility, and soil quality were measured. Biosolids compost increased potato tuber and grain yield in the second year, demonstrating cumulative effects of repeated compost applications. In this study, the value of biosolids compost was primarily as a source of nitrogen, plant available phosphorus, and soil organic matter. A mail survey of 1,374 Skagit County households was conducted to gain insight into community perceptions about the use of biosolids in local agriculture, interest in using biosolids compost as a soil amendment, and desire to participate in local waste management decision-making processes. Mail survey results and participant observation were used to develop a case study of community involvement in waste management research and decision-making in the town of La Conner. This project addressed challenges inherent in conducting research on a controversial topic while developing a new collaborative research model for the region. Scientists, public planners and biosolids managers may be able to build and improve upon what was learned here in their efforts to develop effective regional waste management solutions.