Americans have long believed that one necessary government function is to provide and maintain adequate acreage and facilities for outdoor enjoyment and recreation. Municipal parks and recreation departments are charged with ensuring citizen-access to pleasant, interesting, and well-maintained public recreation. No one knows exactly how many acres are devoted to municipal parks and recreation areas (the city of New York alone has more than 28,000 acres), but all produce vegetative debris from intensive landscaping and maintenance.
Vegetative debris includes leaves, grass clippings, shrub and tree prunings, dead plants, limbs, and trees. This biomass is often discarded in landfills. Twenty-four states have banned the disposal of yard wastes from municipal solid waste landfills but often it can be deposited in inert debris landfills. Once landfilled, vegetative debris decomposes anaerobically (without oxygen), which creates methane—and that, in turn, contributes to global warming. Anaerobic decomposition of wastes in landfills also can cause groundwater contamination.
The vegetative debris from parks and recreation landscaping and maintenance activities is often composted in turned windrows (rows of long piles of mixed wastes). They're aerated by turning the piles periodically either by hand or machine. Typical windrow height, between 4 and 8 feet, allows for a pile large enough to generate sufficient heat and maintain temperatures, yet small enough to allow oxygen to passively flow to the windrow's core. Typical windrow width is between 14 and 16 feet. Actively composting windrows can take from 45 to 120 days.
Windrow operations are considered relatively low-tech and require the most land for composting (approximately 1 acre to process about 4000 cu. yds. annually). Most are open-air facilities, although it is possible to enclose windrow composting in a building.
Manufacturing good compost takes time. In the active composting period, microbes conduct the primary decomposition of the organic material, generally at temperatures higher than 1303 F. The curing period, a lower-temperature aging or maturation process, follows. The time needed depends on many factors, including C:N ratio (carbon:nitrogen), composting method, and degree of active management and weather, but in general, can take from 30 to 60 days for active composting and 60 to 90 days for curing (to read more about manufacturing good compost, click here).