HOW DO REGULATIONS AFFECT MUNICIPAL COMPOST GEOCHEMICAL FINGERPRINTS AND METAL LOADING? A COMPARISON STUDY BETWEEN NORTHERN GERMANY AND BOSTON, MA, USA

Compost is an organic rich humus material used to fertilize agricultural soils. In Germany, the value of compost as a soil enhancer and means of organic waste recycling are recognized. Thus, source separated organic waste collection, municipal compost production, and compost quality control are all regulated at the federal level. German compost quality control includes a benchmark for lead of 150 μg/g. In the United States, none of these measures exist, and as a result urban municipally produced compost can be contaminated with lead and other toxic metals, making it unfit for use in urban gardening. To evaluate the geochemical differences between regulated and unregulated municipal compost, this study measured a suite of major and trace elements using ICP-OES and ICP-MS in samples collected from 5 municipal composting plants in northwestern Germany. Results were compared to previously collected data from Boston, MA. Lead concentrations from the municipal composting site in Boston, MA (n=7) from both the surface of compost piles and within piles ranged from 330-389 μg/g, 2.4 times higher than the German benchmark. Preliminary results from municipal German compost samples (n=10) show lead concentrations ranging from 15 to 50 μg/g, on average 5 times lower than the German benchmark. Source separated waste collection schemes, management standards, and quality control, including heavy metal monitoring, are ensuring the safe production of municipal scale compost in urban to rural settings in Germany. These processes could be implemented in the United States, thus permitting a wider range of end use options for waste municipal carbon.