Trends in Yard Waste Composting

HE TREND toward composting reached its peak in Switzerland in 1975 when approximately 10 percent-or over 200,000 tons-of garbage were composted. However, as garbage production per capita and per year increased ;gin 1960 to 430 kg in 1987, cheminination also accelerated. This led to concern about excessive pollutants in compost and their impact on human health and the environment. Switzerland's reaction to this development was to expand its incinerator capacity. Despite the use of dust filters, intolerable amounts of pollutants escaped with the stack exhaust and ecologically sound methods of disposal had to be found for the combustion residue. This development finally led to the understanding that ecological compatibility and not.price has to be the critical factor for waste disposal. Composting was considered a viable solution provided that the end product had a low content of pollutants and its application would be limited to fertilizing. A series of thorough tests conducted in Switzerland and West Germany resulted in information regarding the sources of heavy metal contents in domestic garbage and demonstrated that the selection of compostable garbage can be based on definable criteria and that compost derived from consistent separation of garbage collection would meet the requirements. This led to the conclusion that the separate collection of yard waste and its subsequent processing into compost could yield a compost acceptable in appearance and level of contaminants, particularly heavy metals. The trend toward yard waste composting has clearly taken hold and has produced, albeit on a small scale, plants with 200 to 25,000 tons annual capacity. The tipping fee for the treatment of organic waste is about $30 to $50 per ton. These new plants also differ greatly from their predecessors due to these facts: Latest research regarding optimal decomposition; The public's pronounced sensitivity towards my types of emission; Strict standards re-