Effect of a Biological Additive on Nitrogen Losses from Pig Slurry during Storage

Use of a wheat straw covering to reduce nitrogen loss during pig slurry storage and reuse of the straw covering in biochar production for nitrogen retention in the slurry

Storing pig slurry (PS) and returning it to the field is one of the most important ways to recycle PS. However, during the storage of PS, the NH3 emissions cause a large loss of nitrogen (N), which reduces the fertilizer value of stored PS and cause environmental pollution. To reduce N loss during PS storage, we added different amounts of wheat straw powder (WSP) and wheat straw segments (WSSs) to the PS. The wheat straw cover was used for biochar production, and then, the biochar was used for N adsorption from the PS. The results showed that the N loss of PS was significantly decreased by use of the wheat straw covering. The N losses in treatments of WSP covering and WSSs covering were reduced by 4.8-53.1 and 0.8-14.2 percentage points compared with that in the control, respectively. Ammonia adsorption is an important reason for the reduction in N loss by straw covering during PS storage. After covering for 180 days in storage, the NH4+-N content in both the WSP covering and WSSs covering increased greatly, and the cover was reused for biochar production. The biochar yield was inversely proportional to the pyrolysis temperature, and the specific surface area and pore volume of the biochar were proportional to the pyrolysis temperature. We achieved the highest amount of NH4+-N adsorption (1.9 mg/g) with a biochar dosage of 0.2 g/L (treatment Y-400). This study provides a new straw-covered PS storage method to achieve straw recycling and low N loss during PS storage.

Improving the Sustainability of Dairy Slurry by A Commercial Additive Treatment

Ammonia (NH3), methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions from livestock farms contribute to negative environmental impacts such as acidification and climate change. A significant part of these emissions is produced from the decomposition of slurry in livestock facilities, during storage and treatment phases. This research aimed at evaluating the effectiveness of the additive “SOP LAGOON” (made of agricultural gypsum processed with proprietary technology) on (i) NH3 and Greenhouse Gas (GHG) emissions, (ii) slurry properties and N loss. Moreover, the Life Cycle Assessment (LCA) method was applied to assess the potential environmental impact associated with stored slurry treated with the additive. Six barrels were filled with 65 L of cattle slurry, of which three were used as a control while the additive was used in the other three. The results indicated that the use of the additive led to a reduction of total nitrogen, nitrates, and GHG emissions. LCA confirmed the higher environmental sustainability of the scenario with the additive for some environmental impact categories among which climate change. In conclusion, the additive has beneficial effects on both emissions and the environment, and the nitrogen present in the treated slurry could partially displace a mineral fertilizer, which can be considered an environmental credit.

Gaseous emissions and modification of slurry composition during storage and after field application: Effect of slurry additives and mechanical separation

The aim of the study was to evaluate the impact of slurry treatment by additives (EU200^® (EU200), Bio-buster^® (BB), JASS^® and sulphuric acid (H₂SO₄)) and mechanical separation on the physical-chemical characteristics, gaseous emissions (NH₃, CH₄, CO₂ and N₂O) during anaerobic storage at ∼20 °C (experiment 1) and NH₃ losses after field application (experiment 2). The treatments studied in experiment 1 were: whole slurry (WS), WS+H₂SO₄ to a pH of 6.0, WS+EU200 and WS+BB. Treatments for experiment 2 were: WS, slurry liquid fraction (LF), composted solid fraction (CSF), LFs treated with BB (LFB), JASS^® (LFJ), H₂SO₄ to a pH of 5.5 (LFA) and soil only (control). The results showed an inhibition of the degradation of organic materials (cellulose, hemicellulose, dry matter organic matter and total carbon) in the WS+H₂SO₄ relative to the WS. When compared to the WS, the WS+H₂SO₄ increased electrical conductivity, ammonium (NH₄⁺) and sulphur (S) concentrations whilst reducing slurry pH after storage. The WS+H₂SO₄ reduced NH₃ volatilization by 69% relative to the WS but had no effect on emissions of CH₄, CO₂ and N₂O during storage. Biological additive treatments (WS+EU200 and WS+BB) had no impact on slurry characteristics and gaseous emissions relative to the WS during storage. After field application, the cumulative NH₃ lost in the LF was almost 50% lower than the WS. The losses in the LFA were reduced by 92% relative to the LF. The LFB and LFJ had no impact on NH₃ losses relative to the LF. A significant effect of treatment on NH₄⁺ concentration was found at the top soil layer (0-5 cm) after NH₃ measurements with higher concentrations in the LF treatments relative to the WS. Overall, the use of the above biological additives to decrease pollutant gases and to modify slurry characteristics are questionable. Reducing slurry dry matter through mechanical separation can mitigate NH₃ losses after field application. Slurry acidification can increase the fertilizer value (NH₄⁺ and S) of slurry whilst mitigating the environmental impacts through a decrease in NH₃ losses during storage and after application.