Occupational hygiene in biowaste composting

Source-separated biowastes from the Helsinki Metropolitan Area have been composted in open air windrows at Ammassuo, the Helsinki regional landfill in Espoo (Finland). The most significant problem encountered in the early stages of the process has been the formation of rancid odor causing human discomfort. The offensive odor was mainly due to carboxylic acids. A total of 110 organic compounds were detected in volatile emissions from windrow composts with an integrated sensory and instrumental method. Occasionally the temperatures in the windrows exceeded 80 degrees C. Bacterial measurements also revealed substantial populations of bacteria at 75 degrees C. The concentrations of airborne microbes and endotoxins were highest during the crushing of fresh biowaste and the turning of compost, and were relatively high in summer and when windrows were dry. The most common fungi in the air were Aspergillus and Penicillium. Dust concentrations were consistently low. The concentrations of microbes were never so high as to constitute an acute health hazard from the occasional exposure. Continuous exposure to such concentrations nevertheless increases the risk of illness. The time, neccessary for the compost to became hygienic improved from four months to four weeks during the project. Drum composting was also tested and was found to be an alternative approach to treating organic wastes. Emissions from the drum composting were low compared to open air composting.