Ammonia and greenhouse gas emissions from co-composting of dead hens with manure as affected by forced aeration rate

Abstract

<p>The effect of ventilation rate (VR) on ammonia (NH3) and greenhouse gas (GHG) emissions from composting piles of dead hens mixed with hen manure was quantified by measuring the gaseous concentrations and airflow rate through the compost bins. Three VR levels of 0.9, 0.7 and 0.5 m³/hr/bin (equivalent to the air exchanges per hour of 0.9, 0.7 and 0.5) were evaluated, each with three replicates. The compost piles were turned once (on day 58) during the 11-wk composting period. Gaseous concentrations of the inlet and exhaust air of the compost bins were measured using a multi-gas infrared photoacoustic analyzer coupled with a multi-channel sampler; VR was measured with a flow meter; and the emission rate (ER) of each gas was computed from the VR and the gas concentration. Decomposition of the carcass over the 11-wk composting period was found to be greater than 88%, as assessed by the reduction in carcass mass. NH3 ER was relatively stable when the compost pile was at high temperatures (~60?). Sharp increase in carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions occurred quickly after construction of the compost pile. VR was found to significantly affect NH3, CO2 and CH4 emissions (p less than 0.05). Specifically, cumulative emissions per kg of initial co-compost matter for the three VR of 0.9, 0.7 and 0.5 m³/hr/bin were, respectively, 2.4, 2.0 and 1.2 g NH3; 78, 66 and 42 g CO2; 120, 90 and 52 mg CH4; and 6.4, 6.1 and 5.1 mg N2O. Hence, the study results suggest that the rate of forced aeration can be adjusted to reduce NH3 and GHG emissions from animal mortality compositing.</p>