Aerated static pile (ASP) composting builds a mixed pile of organic material over an air distribution system and uses blowers, not turning, to supply oxygen and remove heat. The pile stays in place through the active phase while a timer, a temperature sensor or an oxygen sensor decides when the blowers run. Done well, ASP gives an operator direct control of the process on less land than turned windrows, without the building that an in-vessel plant needs.<\/p>\n
The U.S. Environmental Protection Agency describes the method simply: actively aerated static piles use blower systems to move air through the pile, the blowers can be activated by a timer or a temperature sensor, and piles may be covered to help control temperature and moisture. The same EPA overview of composting approaches<\/a> notes that the method works with large quantities and all types of materials.<\/p>\n Three things separate ASP from a turned windrow:<\/p>\n Microbes need carbon, nitrogen, water and air. Cornell Waste Management Institute’s composting pages give working starting points: a carbon to nitrogen ratio of around 30 to 1<\/a>, and a moisture content of 50 to 60%<\/a>, with decomposition slowing when the mix is much wetter than that. Wet, dense, nitrogen-rich feedstocks such as food waste, biosolids and digestate need a coarse, carbon-rich bulking agent (ground wood, wood chips, yard trimmings) to reach those ranges and to hold the pile open. The guide to compost process control<\/a> covers each parameter, and the list of common compost feedstocks covers what each material brings.<\/p>\n In a static pile the bulking agent does the job that turning does in a windrow: it keeps air passages open for weeks. Mix thoroughly, because there is no second chance to blend.<\/p>\n The FAO manual<\/a> gives an initial pile height of about 150 to 245 cm (roughly 5 to 8 feet) for a basic ASP, depending on material porosity, weather and the reach of the loader, and describes building the pile over a base of wood chips or other very porous material that contains the perforated aeration pipe.<\/p>\n A BioCycle design article by Craig Coker and Tim O’Neill, Composting Aeration Floor Functions and Designs<\/a>, sorts aeration floors into two families.<\/p>\n\n
Building the pile: recipe, structure and height<\/h2>\n
Start with the mix<\/h3>\n
Height and base<\/h3>\n
A build-day sequence<\/h3>\n
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Aeration floors and blowers<\/h2>\n
Pipe on grade or in-floor<\/h3>\n