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

A new form of natural aeration static piles, based on Genesis Organic's ver sion of the Passively Aerated Windrow System, was tested by placing a mixtu re of various wood residues and beef manure, weighing 400 kg m(-3), in a pi le 3 m high, 4.3 m wide and 68 m long, on a 45-cm-thick loose base of dry b ark 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% gas eous oxygen, thus acting as a biofilter. Neither ammonia nor hydrogen sulph ide was detectable. Temperatures inside rose to thermophilic range within d ays and that caused the oxygen level to remain within 5% to 15%, adequate f or aerobic decomposition but suitable neither for malodor formation nor for thermochemical oxidation. Five weeks after set-up, the material was screen ed. The >0.64 cm fraction was directed to mixing with new manure, and the r est relaid on the base to the same height and width for hastened maturation . Optimal temperature and oxygen levels were attained within days and maint ained for 75 days. Then followed a mesophilic maturation phase, also aerobi c. Results of bacteriological, chemical and phytotoxicity tests showed that the compost generated was pathogen-free and of high quality.