Covering reduces emissions of ammonia, methane, and nitrous oxide from stockpiled broiler litter

Abstract

Poultry litter, a mix of excreta, bedding material, and discarded feed, is extracted from poultry houses, and used as fertiliser. The litter is often stored in stockpiles outside before field application thereby posing a risk for negative environmental and climatic impact from emissions of ammonia (NH₃) and greenhouse gases (GHG). This study investigated the emissions of methane (CH₄), NH₃, and nitrous oxide (N₂O) from a 22 tonnes broiler litter stockpile over 44 days. The emissions were measured on a farm-scale stockpile with and without coverage using the backward Lagrangian Stochastic method. The results showed distinct emission patterns for each gas during the measurement periods. For all compounds, the emissions during the covered period were significantly lower than during the two uncovered periods. The reduction due to coverage was 92–95% for NH₃, 25–40% for CH₄, and 82–89% for N₂O. NH₃ emissions were highest immediately after coverage removal and during stockpile removal. CH₄ emissions were highest during stockpile removal and lowest during coverage. N₂O emissions were lowest during coverage but a notable increase after coverage removal was observed. The temperature within the stockpile showed variations at different heights, with the highest temperatures recorded in the middle of the stockpile. GHG emissions, based on global warming potential, indicate substantial contributions from N₂O, accounting for 55–72% of emissions in CO₂-equivalents during uncovered periods and 27% during coverage. Furthermore, GHG emissions were reduced 63–72% during coverage compared to the uncovered periods highlighting the importance for immediate coverage of stockpiles to minimise NH₃ and GHG emissions.