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

The dynamics of nitrous oxide and methane emissions from various types of dairy manure at smallholder dairy farms as affected by storage periods

Storing manure emits greenhouse gas (GHG) emissions, including nitrous oxide (N2O) and methane (CH4). However, the emissions from types of manure stored at smallholder dairy farms remains unknown. Hence, the study aims to analyse the dynamics of N2O and CH4 from different types of dairy manure as affected by storage periods. We collected samples from fresh manure (FM-DF1), manure from communal ponds in an urban dairy farm (IP-DF1, FP-DF1, MS-DF1), fresh manure from an urban dairy farm (FM-DF2), and fresh (FM-DF3), separated (FS-DF3), and fermented manure (FR-DF3) from a peri-urban dairy farm, and stored them for eight weeks and analyse them using the closed chamber method. The changes of manure composition including total solids (TS), nitrogen (N), ammonia-nitrogen (N-NH3), and carbon (C) were analysed. Results indicated an increase TS in all treatments except for MS-DF1, while N, N-NH3, and C content decreased in all treatments. The N2O emissions formed at the start, peaked in the middle, and declined towards the end storage period. The CH4 emissions peaked at the start and decreased until the end storage period. Treatment FM-DF2 yield highest cumulative of N2O (0.82 g/m2) and CH4 (41.63 g/m2) compared to other fresh manure treatment. A mixed model analysis detected a significant interaction (p < 0.05) between manure types and storage periods. In conclusion, manure types and storage periods affect the emissions. Changes in manure concentration during storage and animal diets are two important factors influencing emissions. Strategies to reduce emissions include reducing moisture content in manure, shortening storage periods, and improving feed quality.

Effectiveness of mechanical separation for reducing ammonia loss from field-applied slurry: Assessment through literature review and model calculations

To assess solid-liquid separation as a technology to reduce ammonia (NH₃) emission from storage and field application of animal slurry, it is necessary to consider a possible higher NH₃ loss from the solid fraction after application than from raw slurry, as well as losses during storage. A literature review was conducted, and a case study was developed for Denmark, including cattle slurry, pig slurry, and biogas digestate applied by trailing hose, trailing shoe, or open slot injection at five different periods of the year. Standard storage emission factors were used and emission factors after field application were estimated using the ALFAM2 model with input data for dry matter (DM), pH, total ammoniacal nitrogen (TAN), and separation efficiency all from the literature compilation. In general, a clear reduction in the emission factors after application of the liquid fraction was found relative to application of raw slurry in the literature data. Case study results provide some evidence that separation of cattle slurry or digestate, followed by storage and subsequent application by trailing hose or trailing shoe of the liquid fraction and broadcast application of the solid fraction reduces overall NH₃ loss, with a higher reduction when the solid fraction is incorporated by plowing after 4 h. This effect was not present for pig slurry. For all slurry types when the raw slurry and liquid fraction is applied by open slot injection, the overall reduction in emission due to separation is not present or even negative.

Separation efficiency of different solid-liquid separation technologies for slurry and gas emissions of liquid and solid fractions: A meta-analysis

Solid-liquid separation (SLS) technology is widely used in the slurry management in animal farms. This study conducted a comprehensive meta-analysis of 45 published articles to evaluate the differences in separation efficiencies (SE_X-SF) of various SLSs and the changes of gas emissions before and after the separation during on-farm slurry storage. The results indicated that the SE_X-SF of the untreated raw slurry and acidified slurry were consistently greater than those of the digested slurry, and centrifugation resulted in greater SE_X-SF than the other mechanical methods. Both measured and simulated data showed that the centrifuge technology had greater reductions in greenhouse gas (GHG) emissions relative to the screw press (56.1-58.0% vs. 38.9-40.2% for untreated slurry, and 29.7-30.2% vs. 22.5-23.2% for digested slurry), mainly due to CH₄ reduction. Additionally, we identify the need for further assessment of the environmental risks that are associated with SLSs for the development of an optimal slurry management chain.

Environmental implications of stored cattle slurry treatment with sulphuric acid and biochar: A life cycle assessment approach

With the increase of animal slurry produced from livestock production, the monitoring and mitigation of greenhouse gas (GHG) and ammonia (NH₃) emissions represent a major issue. Life cycle assessment (LCA) has been used to evaluate the long-term environmental effects of applied strategies and technologies on cattle slurry management for mitigation of environmental harmful gases. This study was carried on two main aims: first, the effect of the addition of sulphuric acid (SA), biochar (SBi) or A + Bi to liquid cattle-slurry (treated systems) on gas emissions during storage compared to the untreated system (S) was investigated in a laboratory-controlled experiment; second, the environmental implications of each treated or untreated system were assessed through a LCA approach according to ISO 14040/44. Five CML 2001 impact categories were used: eutrophication potential (EP), acidification potential (AP), global warming potential (GWP), human toxicity potential (HTP) and Ozone Layer Depletion Potential (ODP). Comparisons were based on 1 ton fresh dairy cattle slurry. The environmental profile of untreated system showed lower efficiency in mitigation of total GHG and NH₃ emissions (0.0312 and 0.0001 kg CO₂-eq respectively), during storage period and greater impact on GWP and HTP categories. The electricity consumption in mechanical separation dominated the environmental impacts. From the three proposed treated systems, SA showed the highest efficiency on mitigation of gas emissions compared to the other treatments, reducing NH₃, CH₄ and CO₂ emissions respectively in 61%, 98% and 15%, when compared to the SBi system. In all categories, acidified slurry also showed the lowest environmental impact relative to other treated systems and the benefit was more evident when the impacts were expressed per kilogram of nitrogen in the slurry. Therefore, LCA methodology was of great importance to assess the environmental implications of the treatments and acidification can be considered as an effective technique on the mitigation of environmental implications of livestock production and cattle-effluent valorization. Optimization and uniformity of performed studies are essential to validate new strategies to improve the sustainability of this sector in the management of animal wastewater.

Effects of Two Manure Additives on Methane Emissions from Dairy Manure

Simple Summary

Livestock farms often store liquid manure until it can be used to fertilize crops. During anaerobic storage, the manure produces methane, which is a greenhouse gas. Many livestock farms add special chemical products to the manure that are said to control odours or increase fertilizer value. We wanted to know if these additives change the amount of methane produced. Two additives that are commonly used by farmers in many countries were tested in the laboratory. We mixed liquid dairy manure with different amounts of these products and measured the amount of methane produced over 30 to 90 days. Results were then compared to the same manure without any product. These tests were done at two temperatures, around 37 °C (a typical biodigester temperature), and 20 °C (a typical manure storage temperature). We also compared the chemical and physical properties of manure. We found that adding these products did not change the amount of methane produced, and it did not change the chemical and physical properties of the manure related to methane production. These findings suggest that farms using these products can be expected to have normal methane emissions from stored manure.

Abstract

Liquid manure is a significant source of methane (CH₄), a greenhouse gas. Many livestock farms use manure additives for practical and agronomic purposes, but the effect on CH₄ emissions is unknown. To address this gap, two lab studies were conducted, evaluating the CH₄ produced from liquid dairy manure with Penergetic-g^® (12 mg/L, 42 mg/L, and 420 mg/L) or AgrimestMix^® (30.3 mL/L). In the first study, cellulose produced 378 mL CH₄/g volatile solids (VS) at 38 °C and there was no significant difference with Penergetic-g^® at 12 mg/L or 42 mg/L. At the same temperature, dairy manure produced 254 mL CH₄/g VS and was not significantly different from 42 mg/L Penergetic-g^®. In the second lab study, the dairy manure control produced 187 mL CH₄/g VS at 37 °C and 164 mL CH₄/g VS at 20 °C, and there was no significant difference with AgrimestMix (30.3 mL/L) or Penergetic-g^® (420 mg/L) at either temperature. Comparisons of manure composition before and after incubation indicated that the additives had no effect on pH or VS, and small and inconsistent effects on other constituents. Overall, neither additive affected CH₄ production in the lab. The results suggest that farms using these additives are likely to have normal CH₄ emissions from stored manure.

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.

Impact of different treatments on Escherichia coli during storage of cattle slurry

There are different types of effluents from farming operations including untreated slurry (a mixture of manure, urine, split feed, and water), and treated slurry that normally is filtered to separate the solid fraction from the liquid fraction. With the amount of slurry applied on the soils as fertiliser every year, there are necessary to measure the leaching of microbial capable of transmitting infective agents that can be normally on slurry, because slurry can be a potential biohazard capable of transmitting infective agents. The aim of this study was to investigate the presence and survival of Escherichia coli (E. coli) on liquid fraction of dairy slurry, with the addition of different treatments during storage, such as addition of Biochar, beneficial microorganisms, sulphuric acid and the combinations of them. All the applied treatments to slurry show statistically significant differences (P < 0.001), according to the different sampling dates. Results showed that there are conditions and treatments that benefit the survival probability of E. coli, the treatments that include the acidification of slurry have the highest averages of CFU/ml (243288.3 at 37 °C; 136584 at 44 °C). These results can contribute to the improvement of the quality of slurry applied on soils, beneficiating agriculture but also public health.