Large-scale generation of hygienic, high-quality compost from beef feedlot manure and sawmill residues in natural aeration static piles (NASP) without pipes, plenum or envelope

摘要

A new form of natural aeration static piles, based on Genesis Organic's version of the Passively Aerated Windrow System, was tested by placing a mixture of various wood residues and beef manure, weighing 400 kg m~(-3), in a pile 3 m high, 4.3 m wideand 68 m long, on a 45-cm-thick loose base of dry bark that allows convective air movement by the chimney effect. The base and the surficial 15 cm layer were cooler than the core and contained >16 percent gaseous oxygen, thus acting as a biofilter. Neither ammonia nor hydrogen sulphide was detectable. Temperatures inside rose to thermophilic range within days and that caused the oxygen level to remain within 5 percent to 15 percent, adequate for aerobic decomposition but suitable neither for malodor formation nor for thermochemical oxidation. Five weeks after set-up, the material was screened. The >0.64 cm fraction was directed to mixing with new manure, and the rest relaid on the base to the same height and width for hastened maturation. Optimal temperature and oxygen levels were attained within days and maintained for 75 days. Then followed a mesophilic maturation phase, also aerobic. Results of bacteriological, chemical and phytotoxicity tests showed that the compost generated was pathogen-free and of high quality.