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

Abstract

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.

Meta-Analysis of Strategies to Reduce NH3 Emissions from Slurries in European Agriculture and Consequences for Greenhouse Gas Emissions

“…The concealing of animal slurry with different material (plastic, straw, saw-dust, etc.) has been identified as an efficient mitigation strategy for the abatement of NH 3 emission [53,54]. Emission reductions for NH 3 , CH 4 , and CO 2 were achieved by −68% (CI −81, −55), −16% (CI −33, 1), and −31% (CI −45, −17) (Figure 4), respectively, while an increase in emission was noticed for N 2 O, by several orders of magnitude (+13502% (CI −25, +39600)).…”

Emission of Greenhouse Gases and Odorants from Pig Slurry - Effect on the Environment and Methods of its Reduction

“…At the stage of storage, an effective way of lowering the GHG emissions from pig slurry is the storage of slurry in hermetically sealed tanks or in tanks equipped with a special covers, e.g. plastic film cover or combinations of lightweight expanded clay aggregate with lactic acid (common cover materials like straw can increase emissions of methane and nitrous oxide), preferably at a temperature below 15 °C (an experiment conducted in a commercial piggery, emptied of pigs showed that increasing the temperature of slurry from 15 to 20 °C results in doubling of CO 2 emissions), and mixing the slurry just before emptying the tank [20,24,25,29,33]. Berg et al [24] showed that combinations of cover materials (perlite, lightweight expanded clay aggregate or chopped straw) and acidification (using lactic acid) of pig slurry reduces CH 4 and N 2 O emissions during storage effectively [24].…”

“…Operations which reduce GHG emissions from pig slurry during its storage and applying into the soil are: acidification, separation into solid and liquid fractions (however, some authors observed increased emissions after separation of pig slurry into fractions), anaerobic digestion (promotes anoxic processes and biogas (rich in CO 2 and CH 4 ) production, which can be used for electricity and heat production) and aeration (pig slurry aeration lowers CH 4 and CO 2 emissions while increasing N 2 O emission; however, the total effect of GHG emissions is lower in comparison to emissions from pig slurry not subjected to aeration) [8,16,20,25,29,[32][33][34][35]. Bertora et al [35] concluded that the separation of pig slurry reduces the N 2 O emissions with respect to the non-separated slurry.…”

“…The reduction of CH 4 release from pig slurry can also be achieved by the addition of humic acids (reduction of CH 4 emissions by 34 % by improving methanotrophic bacteria) or tannins from quebracho trees (reduction of CH 4 emissions by up to 95 % due to the noxious effects of these compounds on methanogens) [20], while that of N 2 O by spring application of pig slurry on the fields, surface application of pig slurry (e.g. using trailing hoses) and rapid soil incorporation (injection of slurry increases N 2 O emissions from agricultural soils), as well as fertilization with pig slurry subjected to separation into fractions or acidification followed by separation into fractions or acidified liquid fraction of pig slurry [29,[32][33][34][35][36].…”

“…Misselbrook et al [58] demonstrated that covering the pig slurry with a layer of floating clay granules reduced NH 3 emissions by 77 % [58]. Matulaitis et al [33] established that straw cover, sawdust cover and plastic film cover have a high reduction effect on NH 3 emission from the stored pig slurry [33].…”