Ammonia and greenhouse gas emissions from a straw flow system for fattening pigs: Housing and manure storage

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.KeywordsAgricultureGreenhouse gasAmmoniaAbatementMixed crop-dairy systemsOrganicLivestockManureGrasslandCarbon storageSoil carbon sequestration

Anaerobic digestion (AD) of livestock manure is better known for the economic advantage derived from biogas for energy rather than for its environmental benefits. Demonstration of relevant environmental benefits from AD of manure would thus enhance adoption of this technology on animal feeding operations (AFOs). The effect of AD of dairy manure on the emissions of ammonia (NH3) and greenhouse gases (GHG) during manure storage and also in subsequent land applications are presented in this paper. Measurements of GHG emissions from both AD and non-AD manure storages were made using a floating chamber and a photoacoustic gas analyzer (INNOVA model 1412). Emissions of GHG were determined using the standard closed chamber method from field plots applied with AD and non-AD manure. Data obtained indicate significantly higher fluxes of GHG (CO2, N2O, and CH4) from land applied with non-AD manure than from land applied with AD manure. In addition, injection of non-AD manure seemed to further increase CH4 flux from the soil. More than 50% emissions of CO2 and CH4 were observed during the first 3 days after manure was land applied. Emissions of GHG from the anaerobic lagoon holding AD manure, during all four seasons, were significantly lower than from the anaerobic lagoon with non-AD manure. In contrast, the reverse was observed with NH3 emissions. This data demonstrate some environmental benefits for AD of dairy manure prior to its storage and field application but also some potential increased emission of NH3 during storage.

Storage of livestock slurries is a significant source of methane (CH) and ammonia (NH) emissions to the atmosphere, for which accurate quantification and potential mitigation methods are required. Methane and NH emissions were measured from pilot-scale cattle slurry (CS) and pig slurry (PS) stores under cool, temperate, and warm conditions (approximately 8, 11, and 17°C, respectively) and including two potential mitigation practices: (i) a clay granule floating cover (PS) and (ii) slurry acidification (CS). Cumulative emissions of both gases were influenced by mean temperature over the storage period. Methane emissions from the control treatments over the 2-mo storage periods for the cool, temperate, and warm periods were 0.3, 0.1, and 34.3 g CH kg slurry volatile solids for CS and 4.4, 20.1, and 27.7 g CH kg slurry volatile solids for PS. Respective NH emissions for each period were 4, 7, and 12% of initial slurry N content for CS and 12, 18, and 28% of initial slurry N content for PS. Covering PS with clay granules reduced NH emissions by 77% across the three storage periods but had no impact on CH emissions. Acidification of CS reduced CH and NH emissions by 61 and 75%, respectively, across the three storage periods. Nitrous oxide emissions were also monitored but were insignificant. The development of approaches that take into account the influence of storage timing (temperature) and duration on emission estimates for national emission inventory purposes is recommended.

Liquid manure storages are an important source of greenhouse gases (GHG) on dairy farms. Methane (CH4) and nitrous oxide (N2O) are the predominant GHGs, while ammonia (NH3) is an indirect source of N2O. Addition of acid to manure has shown promising emission reductions, however, cost of acidification may be unfeasible for farmers. Fully cleaning storages has also shown to reduce CH4, due to removal of inoculating effects of residual manure (“inoculum”) on fresh manure (FM). However, complete removal of inoculum is practically impossible on large farms, thus acidifying only the inoculum may reduce GHGs without requiring acidification of all FM. This study aimed to quantify the effect of acidified inoculum on CH4, N2O and NH3 emissions from stored manure and quantify the changes in methanogen abundance and activity. Emissions were measured from six 10.6 m3 storages filled with 20% inoculum (1-yr-old manure) and 80% FM. Inoculum was treated in three ways: untreated (control); previously acidified (1-yr prior); and newly acidified with 70% H2SO4 (1.1 L m-3 manure). The CH4 and N2O emissions were continuously measured from June – November using tunable diode trace gas analyzers coupled with venturi air flow systems. The NH3 emissions were measured at 24-h intervals 3 × weekly using acid traps. The activity and abundance of methanogens were quantified by targeting the Methyl Coenzyme M Reductase A (mcrA) gene and transcript which encodes a subunit of the key enzyme that catalyzes the final step of methanogenesis. Bacterial abundance was quantified by targeting the bacterial 16S rRNA gene. Quantifications were performed using quantitative real-time PCR. CH4 emissions were reduced by 77% using newly acidified inoculum and 38% using previously acidified inoculum, compared to the control with untreated inoculum (36.1 g CH4 m-2). Significant treatment reductions in mcrA gene and transcript abundance suggest that CH4 reductions were caused by disruption of methanogen activity. NH3 and N2O emissions were reduced by 33% and 73% using acidified inoculum and 23% and 50% using previously acidified inoculum, respectively, compared to the control. Results suggest that lower acid rates and acidifying less frequently may still have good treatment effects while minimizing cost.

Simple SummaryPrevious studies have shown positive effects of a partially perforated flooring system on animal welfare in broiler housing. Towards the end of the fattening periods, the present study showed a higher ammonia emission rate (NH3 ER) for a partially perforated flooring system compared with a littered control barn. Nevertheless, the measured NH3 concentrations were below 20 ppm, except during a mechanical litter treatment in the winter fattening period. Furthermore, the system offers the possibility of applying practical solutions that were not feasible before. By using underfloor air extraction, manure belts, or acidification systems underneath the elevated perforated area, NH3 concentrations and the resulting NH3 ER could be reduced. Thus, with some optimization, the partially perforated flooring system could be used to contribute to an increase in animal welfare and environmental protection at the same time.A partially (50%) perforated flooring system showed positive effects on health- and behavior-based welfare indicators without affecting production performance. Ammonia (NH3) is the most common air pollutant in poultry production, with effects on animal welfare and the environment. The objectives of animal welfare and environmental protection are often incompatible. Therefore, this study addresses the question of how a partially perforated flooring system affects NH3 emissions. According to German regulations, three fattening periods were carried out with 500 Ross 308 broilers per barn (final stocking density: 39 kg m−2). The experimental barn was equipped with an elevated perforated area in the supply section, accessible by perforated ramps. The remaining area in the experimental barn and the control barn were equipped with wood shavings (600 g m−2). Besides the different floor types, management was identical. Air temperature (Temp), relative air humidity (RH), NH3 concentration, and ventilation rate (VR) were measured continuously. Furthermore, dry matter (DM) content, pH, and litter quality were assessed. Towards the end of the fattening periods, the NH3 emission rate (ER) of the partially perforated flooring system was higher compared with that of the littered control barn (all p < 0.001). This effect is mainly caused by the higher NH3 concentrations, which are promoted by the lack of compaction underneath the elevated perforated area and the increase in pH value under aerobic conditions. Nevertheless, the partially perforated flooring system offers different approaches for NH3 reduction that were previously not feasible, potentially contributing equally to animal welfare and environmental protection.

Livestock manure is a major source of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O). The emissions can be mitigated by production of biogas through anaerobic digestion (AD) of manure, mostly together with other biowastes, which can substitute fossil energy and thereby reduce CO2 emissions and postdigestion GHG emissions. This paper presents GHG balances for manure and biowaste management as affected by AD for five Danish biogas scenarios in which pig and cattle slurry were codigested with one or more of the following biomasses: deep litter, straw, energy crops, slaughterhouse waste, grass–clover green manure, and household waste. The calculated effects of AD on the GHG balance of each scenario included fossil fuel substitution, energy use for transport, leakage of CH4 from biogas production plants, CH4 emissions during storage of animal manure and biowaste, N2O emissions from stored and field applied biomass, N2O emissions related to nitrate (NO3−) leaching and ammonia (NH3) losses, N2O emissions from cultivation of energy crops, and soil C sequestration. All scenarios caused significant reductions in GHG emissions. Most of the reductions resulted from fossil fuel substitution and reduced emissions of CH4 during storage of codigestates. The total reductions in GHG emissions ranged from 65 to 105 kg CO2-eq ton−1 biomass. This wide range showed the importance of biomass composition. Reductions were highest when straw and grass–clover were used as codigestates, whereas reductions per unit energy produced were highest when deep litter or deep litter plus energy crops were used. Potential effects of iLUC were ignored but may have a negative impact on the GHG balance when using energy crops, and this may potentially exceed the calculated positive climate impacts of biogas production. The ammonia emission potential of digestate applied in the field is higher than that from cattle slurry and pig slurry because of the higher pH of the digestate. This effect, and the higher content of TAN in digestate, resulted in increasing ammonia emissions at 0.14 to 0.3 kg NH3-N ton−1 biomass. Nitrate leaching was reduced in all scenarios and ranged from 0.04 to 0.45 kg NO3-N ton−1 biomass. In the scenario in which maize silage was introduced, the maize production increased leaching and almost negated the effect of AD. Methane leakage caused a 7% reduction in the positive climate impact for each percentage point of leakage in a manure-based biogas scenario.

Methane, nitrous oxide and ammonia emissions during storage and after application of dairy cattle slurry and influence of slurry treatment

Management of livestock manure may recycle nutrients and decrease greenhouse gas (GHG) and ammonia (NH3) emissions. The objectives were to ascertain effects of environmental conditions and turning on methane (CH4), nitrous oxide (N2O), and NH3 emissions and if treatment with 8.5 g of dicyandiamide (DCD), a denitrification agent, altered GHG emissions. Manure and bedding were collected from feedlot pens and used to construct 3 piles (~1.9 m3 volume) each in winter (WI) and spring (SP). WI piles were turned once, and SP piles were turned twice. Methane, N2O, and NH3 emissions were collected. Methane and N2O flux measurements were collected from SP piles using a static chamber (3.7m L x 2.2m W x 0.9m H). Initial dry matter and nitrogen contents were 33.2 and 30.0% and 20.1 and 17.7 g/kg in WI and SP piles, respectively. Average ambient temperatures and wind speeds were 0.3oC and 10.7oC and 1.76 m/s and 1.97 m/s during WI and SP, respectively. Internal temperatures reached 51±3.9oC on d 4–11 and gradually decreased. Normalized CH4 averaged 2.19 mg٠s٠m-4 and N2O emissions averaged 0.84 mg٠s٠m-4, and were not different between the WI and SP piles. Turning did not affect CH4 emissions from WI piles, but were 55% greater (P &amp;lt; 0.05) when SP piles were turned a second time. Emissions of N2O increased 51% when WI and SP piles were turned (P &amp;lt; 0.05). Ammonia emissions were 83.5% greater from WI piles due to their higher initial concentrations of NH4+-N (2.21 vs. 1.11 g/kg; P &amp;lt; 0.05). Turning did not influence CH4 and N2O fluxes. Addition of DCD at pile formation appears to decrease N2O emissions and fluxes 3 and 10 d later. Turning management and season impacted overall CH4, N2O, and NH3 emissions. Fine-tuning manure handling and management during different seasons may effectively reduce GHG and NH3 emissions.

Greenhouse gas and ammonia emissions from digested and separated dairy manure during storage and after land application

Curbing Livestock Emissions: ammonia, greenhouse gases, and odors

Slurry storage is a significant source of NH3 and greenhouse gas (GHG) emissions. The aim of this laboratory study was to assess the effects of different chemical additives and biochars on the emissions of NH3, N2O, CO2, and CH4 during the short-term storage of pig slurry. The experiment was performed using Kilner jars filled with raw slurry as control and six treatment additives (5% w/w): acidified slurry, alkalinized slurry, neutralized slurry, agroforestry biochar, cardoon biochar, and elderberry biochar. The gas emissions were measured for 30 days, and the composition of the slurries was determined. During short-term storage, the results of this laboratory study indicated that the NH3 emissions were reduced by 58% by acidification and by 20% by the biochars (Agroforestry, Cardoon, and Elderberry treatments), while neutralization reduced this loss by only 12%. Nitrous oxide emissions were not reduced by the chemical additives (Acidified, Alkalinized, and Neutralized treatments), while this loss was increased by 12% by the biochars. Carbon dioxide, CH4, and global warming potential emissions were not affected by the chemical additives and biochars. Furthermore, the absence of differences between the biochars may be related to their similar composition. Regarding the influence of the studied additives on NH3 losses, it can be concluded that acidification was the best mitigation measure and the biochars were quite similar due to their composition. Furthermore, neutralization had the advantage of sanitizing the slurry, but only had a mild impact on NH3 preservation.

Responses of CH4, N2O, and NH3 emissions to different slurry pH values of 5.5–10.0: Characteristics and mechanisms

Observations of production and emission of greenhouse gases and ammonia during storage of solids separated from pig slurry: Effects of covering

Pig farms have achieved importance in the last few decades from the perspective of environment protection as a consequence of the intensive rearing systems in livestock production. Ammonia (NH3) and greenhouse gases (GHG), such as methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O), are emitted from slurry storage at farm prior to land application, but little is known about these losses under on-farm conditions in Spain. This study assessed the influence of management and environmental parameters on NH3 and GHG emissions from slurry storage in spring and autumn. Gas emissions were measured in a commercial pig-fattening farm from two lagoons (1000 and 768 m3 capacity, respectively) during 30 days by the floating dynamic chamber system in spring and autumn 2011 (average temperature 19 and 9 °C, respectively). Low NH3 and CH4 emissions were registered in spring (range 10–406 and 3–17 mg m−2 min−1, respectively) probably as a result of low pH values of stored slurry (6.5 to 7.0) and rainfall. High variability on NH3, CH4, and CO2 emissions was observed as a result of differences in temperature and rainfall. No NH3 emission and low CH4 and CO2 emissions were observed in autumn (average 1.2 ± 0.9 and 27 ± 22 mg m−2 min−1, respectively). Slurry loading operations increased NH3 losses from storage.