Liquid manure storages are sources of greenhouse gases (GHGs) and ammonia (NH₃). Reducing these emissions is desirable. Adding a floating permeable cover to the storage is one approach to achieving emission reductions. Floating covers have the advantage of being affordable and adaptable to many storage configurations. Previous research has shown that covers can be effective at reducing some emissions (often NH₃) while increasing others (often nitrous oxide (N₂O) and carbon dioxide (CO₂)). The first objective of this research was to simultaneously characterize the emissions of methane (CH₄), N₂O, CO₂, and NH₃ from stored liquid dairy manure in winter, spring, and summer.

Liquid manure becomes stratified while it is stored. To facilitate pumping and subsequent land application, storages are often mechanically homogenized prior to being emptied. This presents an important disturbance that may strongly affect emissions. Thus, the second objective of this research was to assess the emissions during mixing. The two emission components (undisturbed storage, and mixing) are then combined to determine the overall effect of covers on emissions during storage.

The research was conducted in six pilot-scale manure storages (6.6 m²). To determine gas flux, dynamic chambers were placed over the storages. Inlet and outlet concentrations of GHGs were continuously measured, using absorption spectroscopy (tunable diode laser; infrared gas analyzer). Concentrations of NH₃ were determined using a gas washing technique. The slurries were mixed using electric boat motors situated inside the chambers. Results from an experiment using dairy manure and straw covers will be discussed. Uncovered controls were used as a reference.