DECADAL CHANGES IN CITY OF BOSTON MUNICIPAL COMPOST: IDENTIFYING BEST MANAGEMENT THROUGH GEOCHEMISTRY AND PARTICIPATORY ACTION RESEARCH

Municipal composting is an important waste disposal strategy in urban areas, as the compost product can be used as a resource in sustainable urban agriculture and minimize the resuspension of legacy lead contaminated soils in high risk communities. Changes in feedstock sources, such as the presence of fugitive metal inputs and different carbon concentrations, for municipal compost has implications for quality of compost produced. In particular, lead (Pb) contamination of municipal compost is a concern for the City of Boston and its sustainable agriculture practitioners. Partnering with The Food Project, a non-profit organization engaged in sustainable agriculture in Boston, we collected samples and tracked changes in the bulk lead concentrations in City of Boston municipal compost since 2006. We observed a factor of two changes in bulk lead concentrations from 2006-2012, during a time when curbside pickup of yard waste efforts increased. Drawing upon participatory action research principles, we ask informed questions that address local risks, incorporate community resources, and refine strategies that will have long-term benefits for the community as a whole. Such strategies include maximizing municipal compost as an affordable bioremediation strategy, given local lead concentrations in <37 micron sized in situ soils can exceed EPA benchmarks by a factor of 5-10 times. We have developed a trace/major element ratio model that can fingerprint the main feedstocks (e.g. food waste, yard green waste (curbside pick up), parkland brown waste, and loam) that comprise the final compost. Geochemically identifying the specific compositional shifts in feedstock will permit cities to design municipal compost to meet a range of end uses, including use in community gardens. Ongoing research to examine the effects of additional bioinspired materials on pH and C/N ratios will inform decisions that may maximize the matrix’s potential as a growth medium while minimizing liable pools of lead. More specifically, the change in feedstock may affect the pH and thus the bioavailable fraction of lead. This study focuses on source changes to the matrix of compost and the relationship between these changes, pH, and bioavailability in municipal compost.