Composting High Moisture Content Bovine Manure Using Passive Aeration

Compost Science & Utilization, (2004), Vol. 12, No. 3, 249-267

I.G. Mason*, M.S. Mollah, Ming Feng Zhong and G.J. Manderson
Institute of Technology & Engineering, Massey University, Palmerston North, New Zealand

High moisture content bovine manure from a farm dairy (milking parlor) holding yard was successfully composted in a pilot-scale passively aerated system, without prior dewatering, using sawdust or paper as amendments and woodchips as the bulking agent. The amendments were used to adjust the manure total solids content from an initial average level of 10% (w/w) to approximately 20% (w/w), prior to structural conditioning with the woodchips. Initial total solids levels for the mixture were approximately 35% (w/w) in both cases. Rapid temperature increases were obtained and peak values of 73.9°C and 79.5°C were recorded for the sawdust and paper amendment systems respectively. Thermophilic conditions were maintained in the pile centers for 17-54 days and temperatures above 55°C for 6-37 days. However, susceptibility to environmental influences was demonstrated, with downward temperature excursions, coincident with cool ambient conditions, recorded on several occasions. Final mixture moisture levels were approximately 56-58% (w/w) for the sawdust amendment system and 44-49% (w/w) for the paper amendment system. Marked vertical differences in moisture concentration were found in both manure/amendment/woodchips systems, with notably drier conditions in the lower layers of the paper amendment piles. Predicted initial ratios of available energy to total moisture were 438-949 and 563-1146 cal/g-H2O for the sawdust and paper amendment systems respectively, depending on the biodegradability factor assumed for the woodchips component. Energy usage values of 1730 and 1344 cal/g-H2O-removed were determined for the sawdust amendment system, based on measured VS and moisture changes. Overall biodegradability factors for the sawdust amendment replicates, based on volatile solids removal, were 0.29 and 0.33 and the composting performance of both systems results indicated that the woodchips had likely contributed substantially to the biodegradable volatile solids pool. Overall disinfection performance after 70-74 days was limited, with a maximum coliform removal of 2.2 log MPN/g-TS. Composting of manure and sawdust alone resulted in a slow rate of temperature rise and incomplete composting after 90 days. Further work is suggested in order to explore the effect of pile insulation or partial enclosure and to study moisture distribution, woodchips biodegradability, materials handling and disinfection performance issues

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