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

Anaerobic digestion, solid-liquid separation, and drying of dairy manure: Measuring constituents and modeling emission

Swine production in temperate and tropical environments: W.G. Pond and J.H. Maner. Freeman, San Francisco, Calif., 1974, 646 pp., US $ 17.50

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.

Livestock operations deploy increasingly complex facilities and technologies in manure management to reduce negative environmental impacts and to improve the agronomic value of manures. To capture and quantify processes of degradation, conversion and emission of manure constituents in these complex systems, this study presented a newly developed modular manure management (FarmM3) model. Using this model, we simulated flows and losses of manure organic matter (OM), carbon (C), nitrogen (N), phosphorus (P) and potassium (K) from manure management chains (MMCs) with deep litter, anaerobic lagoon, solid-liquid separation (SLS), anaerobic digestion (AD), and combinations of SLS and AD. The sensitivity of degradation and losses of manure constituents to changes in the configuration and parameters of MMCs was assessed. Results showed the MMCs with deep litter and AD led to higher OM degradation, C losses and greenhouse gas (GHG) emissions due to the substantial amounts of straw added to bedding and the digester. A trade-off between GHG and ammonia emissions was identified in the MMCs with deep litter. Application of SLS could reduce GHG emissions by 40% to 60% due to reduced methane and nitrous oxide emissions from separated liquid fraction storage. A stronger reduction of ammonia emission was observed when applying SLS to digested slurry than to raw slurry. Sensitivity analysis showed that the N loss was most sensitive to N transformation in the MMC with deep litter, and was most affected by the loss coefficients of ammonia during liquid manure storage and application in MMCs with SLS and AD. Losses of P and K from MMCs with SLS were influenced by separation efficiencies from SLS and loss coefficients from solid fraction storage. The impact of model input parameters on GHG emissions highly depended on the selected manure management facilities. This study shows that manure management facilities have a strong influence on the fate of manure constituents. The FarmM3 model can be used to quantify the degradation and losses of different manure constituents in complex MMCs and the effects of manure treatment facilities, and to identify the most important parameters determining these losses.

Field and laboratory studies were conducted to evaluate the effects of anaerobic digestion (AD) and solids-liquid separation on emissions during subsequent storage and land application. The lab storage tests were conducted for 21 days with manure samples obtained at the following four points in a full-scale AD system: raw manure (RM) delivery, raw manure supplemented with other substrates (AD influent), AD effluent, and AD effluent after solids-liquid separation (AD liquid effluent). Ammonia fluxes from stored AD effluent declined from 3.95 to 2.02 g m−2 day−1. Lower NH3 fluxes, however, were observed from AD liquid effluent (1.1 g m−2 day−1) and AD influent (0.25 g m−2 day−1). Ammonia emissions from full-scale manure storages were similar to those obtained in the lab. Results also indicated significantly lower volatile fatty acid (VFA) in AD effluent and AD liquid effluent compared with that from the AD influent, indicating significant reduction in odor generation potential due to AD and solids-liquid separation processes. Two manure application methods (surface application and manure injection) for both non-AD and AD manures were simulated in the lab and studied for 9 days. Surface-applied non-AD manure exhibited the highest NH3 flux (0.78 g m−2 day−1), while injected AD manure led to the lowest NH3 flux (0.17 g m−2 day−1). Similar NH3 emissions results were observed from the field studies. Overall, while AD of dairy manure resulted in significant increases in NH3 emissions from stored effluent, the AD process significantly reduced NH3 emissions following application of AD manure on land.

Managing food waste is key to tackling climate change

Life cycle assessment of sludge anaerobic digestion combined with land application treatment route: Greenhouse gas emission and reduction potential

A review of mitigation technologies and management strategies for greenhouse gas and air pollutant emissions in livestock production

Mitigating Curtailment and Carbon Emissions through Load Migration between Data Centers

Animal manure contributes considerably to ammonia (NH3) and greenhouse gas (GHG) emissions in Europe. Various treatment technologies have been implemented to reduce emissions and to facilitate its use as fertilizer, but a systematic analysis of these technologies has not yet been carried out. This study presents an integrated assessment of manure treatment effects on NH3, nitrous oxide (N2O) and methane (CH4) emissions from manure management chains in all countries of EU-27 in 2010 using the MITERRA-Europe model. Effects of implementing 12 treatment technologies on emissions and nutrient recovery were further explored through scenario analyses; the level of implementation corresponded to levels currently achieved by forerunner countries. Manure treatment decreased GHG emissions from manures in EU countries by 0-17% in 2010, with the largest contribution from anaerobic digestion; the effects on NH3 emissions were small. Scenario analyses indicate that increased use of slurry acidification, thermal drying, incineration and pyrolysis may decrease NH3 (9-11%) and GHG (11-18%) emissions; nitrification-denitrification treatment decreased NH3 emissions, but increased GHG emissions. The nitrogen recovery (% of nitrogen excreted in housings that is applied to land) would increase from a mean of 57% (in 2010) to 61% by acidification, but would decrease to 48% by incineration. Promoting optimized manure treatment technologies can greatly contribute to achieving NH3 and GHG emission targets set in EU environmental policies.

Identifying novel flocculants to improve the separation efficiency of dairy slurries is important to facilitate slurry recycling with a low carbon footprint. Two microcosm experiments were conducted to differentiate ammonia (NH3), nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) emissions from liquid and solid fractions obtained using conventional (mechanical separator) and enhanced (flocculant + mechanical separator) solid–liquid separation (SLS) methods during the storage and soil application phases. Tannic acid (TA) was investigated as a potential flocculant in order to explore its effectiveness in reducing greenhouse gas (GHG) emissions during the storage and soil phases. Compared to the conventional SLS method, the employment of the enhanced SLS method reduced GHG emissions during the storage and soil application phases by 53.64% and 31.63%, respectively, thereby leading to an integrative mitigation of GHG emissions across the storage and soil application chain; however, it strongly increased NH3 emissions by 70.96% during the soil application phase, demonstrating a higher risk of gaseous N loss. Meanwhile, large trade-offs in N2O, CH4, and NH3 emissions between the solid and liquid fractions during the storage phase were observed, and the reduced CH4 and NH3 emissions during the storage phase were also partly offset by increased emissions during the soil application phase. In conclusion, enhanced separation technology using tannic acid as a flocculant can reduce GHG emissions from the management chain, with synergistic mitigation of CH4 and N2O, but the risk of increased NH3 emissions requires further attention. This study may be helpful in mitigating GHG emissions and recycling plant-derived tannic acid in the circular agriculture context.

Abstract. Several strategies are available for mitigating greenhouse gas (GHG) emissions associated with dairy manure management in barns, storage units, and fields. For instance, incorporation of manure into the soil, solid-liquid separation, composting, enclosed manure storage, and anaerobic digestion have been identified as good options. However, these strategies are not widely adopted in Canada because clear information on their effectiveness to abate the whole-farm GHG footprint is lacking. Better information on the most cost-effective options for reducing on-farm GHG emissions would assist decision making for dairy producers and foster adoption of the most promising approaches on Canadian dairies. In this context, whole-farm modeling provides a tool for evaluating different GHG abatement strategies. An Excel-based linear optimization model (N-CyCLES) was used to assess the economics and the nutrient and GHG footprints of two representative dairy farms in Québec, Canada. The farms were located in regions with contrasting climates (southwestern and eastern Québec). The model was developed to optimize feeding, cropping, and manure handling as a single unit of management, considering the aforementioned mitigation options. Greenhouse gas emissions from the different simulated milk production systems reached 1.27 to 1.85 kg CO2e kg-1 of corrected milk, allowing GHG reductions of up to 25% compared to the base system described in Part I. Solid-liquid separation had the greatest GHG mitigation potential, followed by the digester-like strategy involving a tight cover for gas burning. However, both options implied a decrease in farm net income. Manure incorporation into the soil and composting were associated with high investment relative to their GHG abatement potential. The most cost-effective option was using a loose cover on the manure storage unit. This approach lessened the manure volume and ammonia-N volatilization, thereby reducing fertilizer and manure spreading costs, increasing crop sales and profit, and enhancing the whole-farm N and GHG footprints. Consequently, covering the manure tanks appears to be an economically viable practice for Québec dairy farms. Keywords: Anaerobic digestion, Composting, Dairy cow, Farm net income, Greenhouse gas emission, Incorporation, Nutrient footprint, Solid-liquid separation, Storage cover, Whole-farm model.

In this study, we demonstrate that the addition of earthworm castings (EC) in kitchen waste composting reduces ammonia and greenhouse gas (GHG) emissions and improves compost maturity. Kitchen waste (KW) was mixed with sawdust at a ratio of 7:3 as the compost stock. Four treatments with different proportions of EC added (0%, 2.5%, 5.0%, and 7.5% on the basis of the initial kitchen waste mass) were designed and utilized in a composting process lasting 85 days. The results showed that the GHG and ammonia emissions were considerably reduced in the treatments with EC added. In addition, EC amendment prolonged the thermophilic stage and shortened the composting period. The addition of EC reduced ammonia, methane, and nitrous oxide emissions by 61%, 48%, and 94%, respectively, also indicating that nitrogen in the compost was conserved. Nitrogen and major nutrients were best preserved in the EC 7.5% treatment, which produced a compost product with a better nutrient profile. Furthermore, the total global warming potential of the KW composting process was reduced by 74% by using the mixture with EC. An effective reduction in GHG emissions was observed already with the addition of 2.5% EC, but a significant reduction in ammonia emissions was observed for the EC 7.5% treatment. Therefore, the results of this study suggest that EC is an effective additive in KW composting. More specifically, addition of EC at 7.5% of the initial KW mass was most recommendable for mitigating potential global warming effects and improving compost quality.