The effect of floating covers on gas emissions from liquid pig manure

Livestock manure is the source of different pollutant gases that can generate soil acidification, eutrophication, and contribute to global warming, or have a negative impact on health. Covers can control gas emissions from manure, but their impact is still under discussion. The aim of this experiment was to study the effect of different covers on methane (CH₄₎, nitric oxide (NO), hydrogen sulfide (H₂S), ammonia (NH₃), carbon monoxide (CO), and carbon dioxide (CO₂) emissions from liquid pig manure. Six types of floating covers were tested: light expanded clay aggregate (leca), peat, sunflower oil, sawdust, straw, and plastic film. Manure was stored at 5, 15, and 25 °C for 37 d. Gas emissions were measured from the headspaces of the dynamic chambers. The results of our study showed that both cover and temperature have a noticeable impact on gas emissions from liquid pig manure. The plastic film cover was the most efficient at all tested temperatures because it reduced emissions of all the measured gases. In this case, mean emission reductions were: CH₄ 91.5% (P < 0.01), NO 92.0% (P < 0.05), H₂S 78.1% (P < 0.05), NH₃ 54.7% (P < 0.01), CO 98.4% (P < 0.01), and CO₂ 67.1% (P < 0.01). Other covers had an inconsistent impact on separate gas emissions. However, covers generally helped to decrease NH₃, H₂S, and CO₂ emissions.