|SCHMIDT, A - Mississippi State University|
|DAVID, J - Mississippi State University|
|KIESS, A - Mississippi State University|
Submitted to: International Symposium on Air Quality and Waste Management for Agriculture
Publication Type: Proceedings
Publication Acceptance Date: 7/7/2010
Publication Date: 9/13/2010
Citation: Schmidt, A.M., David, J.D., Purswell, J.L., Kiess, A.S. 2010. Effect of moisture content on the heating profile in composted broiler litter. International Symposium on Air Quality and Waste Management for Agriculture. ASABE #711PO510.
Interpretive Summary: Windrowing of broiler litter has been employed to condition recycled litter prior to chick placement. Internal windrow temperature is dependent upon microbial activity, which is influenced by water activity. Simulated windrows were constructed to assess the effects of moisture content on heating patterns in windrowed litter. Litter moisture contents between 30 and 35% were found to provide maximum heat generation during the tests. Published time-temperature goals to reduce pathogens may not be achievable in windrowed litter, even with added moisture.
Technical Abstract: Moisture content can affect the magnitude of heat generation during composting. Temperature was recorded every 2 min for 7 d at 10-cm increments throughout the vertical profile of broiler litter treated with five quantities of water addition. Water additions were applied to achieve litter moisture contents of 25, 30, 35, 40, and 45% MC w.b. Broiler litter moisture content between 30 and 35% was found to provide maximum heat generation during composting. Mean maximum temperature across all treatments was highest at the 10 and 20 cm litter depths. No moisture content treatment generated temperatures of required durations to meet all aspects of the EPA 503b rule for class B compost standards. Populations of total culturable aerobes, total culturable anaerobes and total culturable coliforms were enumerated in raw litter (time 1) and in treated litter after 84 h of composting (time 2) to determine if changes in population density were apparent. Over the 84 h composting period, a 4-log10 reduction in aerobes and coliforms was found for litter samples where a temperature of 40°C was sustained for as little as 4 h. Populations of total culturable anaerobes were reduced from time 1 to time 2, though the reduction was not physiologically relevant. The results demonstrate that incorporation of water to achieve a litter moisture content between 30 and 35% provides for greater heating during litter composting. Published time-temperature goals for pathogen reduction may not be achievable even with the added moisture, though relevant reductions in total culturable aerobes and coliforms were demonstrated with 84 h of composting.