Liquid manure storage temperature is affected by storage design and management practices—A modelling assessment

A numerical model was used to predict effects of different liquid manure storage designs and management practices on manure temperature (Tm). Manure storage designs included various tank diameters, proportion of the storage above-ground, addition of a roof, and floating covers (synthetic or straw). Manure management practices included the frequency of manure removal, manure agitation, and the depth of manure remaining after removal. Results showed that smaller diameter tanks with a greater depth had lower peak Tm. There was no appreciable effect on Tm from constructing a storage tank above-ground vs in-ground. Adding a roof decreased peak Tm for spring manure removal, but not autumn removal. Floating synthetic covers with high solar absorptivity (i.e. dark colour) greatly increased peak Tm, whereas straw covers had the opposite effect—decreasing peak Tm. Removing manure twice per year (spring and autumn) or once annually in spring led to shallower manure depth in summer and greater peak Tm; in contrast, once annual autumn removal had greater depth and lower peak Tm in summer. Manure agitation during the warm season increased peak Tm substantially for autumn manure removal, and slightly for spring removal. Leaving less manure in storage after spring removal led to a more rapid increase in Tm and a higher peak Tm in summer. Overall, the study highlights that manure storage design and management practices can greatly affect Tm, with peak Tm being increased or decreased up to 8°C in some scenarios. These findings emphasize that Tm is dynamic and that air temperature is an overly simplistic surrogate for Tm. Thus, it is important that studies examining greenhouse gas emissions from liquid manure also measure manure temperature. Insights from the study may guide future research linking liquid manure storage design and management to Tm and related effects on greenhouse gases such as methane.