Methane and Nitrous Oxide Emissions from Outdoor-Stored Broiler Litter

Handling and storage of a variety of types of agricultural wastes results in the formation and release of nitrous oxide (N2O) and methane (CH4) gases to the atmosphere. These gases contribute to climate change through the greenhouse effect. Few studies however have examined evolution of these gases from poultry litter. N2O is a by-product of nitrification and an intermediate product of denitrification, and is often produced when both aerobic and anaerobic conditions are present. CH4 emissions, however, are associated with anaerobic reactions. Outdoor storage of broiler litter provides an excellent media for which both aerobic and anaerobic zones can coexist, particularly when the litter is of varying ages from multiple broiler cycles. It provides a large amount of nitrogen for bacterial nitrification/denitrification processes as well as carbon to support anaerobic bacterial fermentation. The objective of the study was to quantify N2O and CH4 emissions for broiler litter stored in an uncovered outdoor bunker by conducting full-scale field experiments. A modified micrometeorological mass balance approach was used to monitor emissions from stored broiler litter in a three-walled concrete bunker. Air concentrations of N2O and CH4 were measured using tuneable-diode laser spectroscopy. Experiments over the course of approximately 65 days yielded average emission rates of approximately 18µg m-2 s-1 and 75µg m-2 s-1 for nitrous oxide and methane respectively.