Addition of Straw or Sawdust to Mitigate Greenhouse Gas Emissions from Slurry Produced by Housed Cattle: A Field Incubation Study

Ammonia and greenhouse gas emissions from slurry storage - A review

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

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.

Agricultural ecosystems are significant sources of reactive trace gases, such as ammonia and nitric oxide, as well as greenhouse gases (GHGs), including carbon dioxide, methane, and nitrous oxide. These emissions contribute to global warming, air pollution, and ecosystem eutrophication. Traditional mitigation strategies, such as sulfuric acid slurry acidification in slurry storage, reduce ammonia and methane emissions effectively but face high costs, safety concerns, and restrictions in organic farming. This study explores alternative amendments for slurry, including organic acids waste i.e. cheese whey (a dairy byproduct), sauerkraut juice (a fermentation byproduct), and leonardite (a humic-rich natural material), to assess their potential for emission mitigation.Using a controlled soil-plant mesocosm system to simulate field-like conditions under a laboratory setting, emissions of ammonia, methane, nitrous oxide, nitric oxide, and carbon dioxide were continuously monitored over nine days. Flux rates were determined using the dynamic chamber method at a temperature of 18°C and a water-filled pore space of 50%. The mesocosms were treated with either untreated slurry, slurry amended with cheese whey, sauerkraut juice, or leonardite, or left unfertilized as a control.Results highlighted the potential of cheese whey and sauerkraut juice to substantially lower ammonia emissions by as much as 91%, with cheese whey also reducing combined GHG emissions significantly. While sauerkraut juice showed promise in reducing methane emissions, nitrous oxide emissions were elevated due to a higher ammonium content in the slurry-amendment mixture. Leonardite, though not effective in mitigating ammonia emissions, demonstrated its utility in lowering GHG emissions overall.The findings suggest cheese whey and sauerkraut juice as promising amendments for ammonia reduction, with leonardite offering potential for GHG mitigation. However, the trade-offs observed with nitrous oxide emissions emphasize the need for further optimization to achieve a balanced mitigation strategy. These results contribute to the understanding of gas exchanges in agricultural ecosystems and promote sustainable practices by repurposing agricultural byproducts in a circular economy.

Effect on greenhouse gas emissions (CH4 and N2O) of straw mulching or its incorporation in farmland ecosystems in China

HighlightsLab-scale beef manure bedded packs were constructed to evaluate the temperature effect on gaseous emissions.Temperature had a tendency to increase ammonia, hydrogen sulfide, and greenhouse gases in the headspace above bedded packs over time.Abstract. Throughout the Upper Midwest, producers have observed increased land and fertilizer prices, resulting in increased popularity of confinement feeding facilities such as mono-slope and hoop barns with bedded packs. Environmental and public pressure has been placed on the agriculture community to reduce ammonia (NH3), hydrogen sulfide (H2S), and greenhouse gas (GHG) emissions from concentrated animal feeding operations (CAFOs). This study was conducted to determine the effects of bedding material (corn stover (CS), bean stover (BS), wheat straw (WS), or pine wood chips (PC)) and ambient temperature (15°C (COOL) or 30°C (HOT)) on NH3, CH4, CO2, N2O, and H2S flux in air samples collected in the headspace above lab-scale bedded packs. All bedded packs were housed at 18°C for an initial three weeks before being placed in their respective environmental chambers at 15°C or 30°C for the remainder of the 6-week study period. Significant two-way interactions of bedding material by temperature for NH3 flux were observed (p = 0.0094). Ammonia flux was greater at higher temperature, while CS bedding had the lowest NH3 emissions compared to the other bedding materials. A significant two-way interaction of bedding material by temperature for H2S flux was observed (p < 0.0001), with significantly greater H2S produced in the headspace of COOL-BS packs compared to all other treatments. Additionally, a significant (p = 0.0357) two-way interaction of temperature by age of the bedded pack was observed for H2S flux. Hydrogen sulfide flux appeared to be influenced by low bedded pack pH to a greater extent than by increase in temperature. Greenhouse gas emissions tended to be higher from bedded packs in HOT treatments. A significant (p = 0.0422) interaction among bedding material, temperature, and age of the bedded pack was observed for CH4. Significantly greater CH4 flux was observed in the headspace above HOT-BS and HOT-CS at week 6 compared to all other treatments. A significant two-way interaction of bedding material by temperature was observed for CO2 flux (p = 0.0189). The largest CO2 levels were observed above WS bedding material regardless of temperature. Nitrous oxide flux decreased over the 6-week study for all bedded packs, while WS and PC bedded packs produced the greatest N2O flux. The results indicate that feedlot operators maintaining bedded pack facilities will have the greatest reduction in NH3 emissions when using CS bedding, regardless of ambient temperature. To reduce CH4 emissions, producers should avoid allowing BS and CS bedded packs that are maintained for longer than six weeks in HOT (30°C) temperatures; frequent cleaning during summer months is recommended. Based on the CO2 equivalents of CH4 and N2O, producers should consider PC as an option to reduce GHG emissions. Keywords: Ammonia, Bedding age, Bedding type, Beef, Carbon dioxide, Greenhouse gas, Hydrogen sulfide, Methane, Nitrous oxide, Temperature.

Mitigation of ammonia and greenhouse gas emissions from stored cattle slurry using acidifiers and chemical amendments

Animal agriculture has been found to be a major contributor of aerial ammonia and greenhouse gases such as carbon dioxide, nitrous oxide, and methane particularly from manure handling and storage. Dairy cattle managed on bedded packs are becoming more common in Pennsylvania. A focus of this research was to reduce ammonia and greenhouse gas emissions from semi-solid dairy manure storage using compaction as the treatment method. Dairy manure with various bedding materials (woodchips, sawdust, or hay) was characterized in terms of moisture content and surface area in relation to mechanical strength and porosity. Sawdust and woodchips have a larger surface area than hay so use as a bedding additive can reduce the moisture content of manure and yield a higher mechanical strength when compacted. The results revealed that sawdust had a greater porosity even under compaction. This caused more carbon dioxide to be released and less methane because aerobic conditions were presumably maintained within the pile. Greater moisture content in the hay bedded material was conducive to anaerobic conditions with increased methane release. The effectiveness of moderate compaction as a treatment method to reduce ammonia and greenhouse gas emissions is still inconclusive; however, decreases in gas emissions were observed when bulk densities were increased to over 600 kg*m-3.

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.

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.

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

Gaseous emissions are the main loss pathways of nutrients during dairy slurry storage. In this study, we compiled published data on cumulative ammonia (NH3), nitrous oxide (N2O) and methane (CH4) emissions from dairy slurry storage and evaluated the integrated effects of slurry pH, total solids (TS), ambient temperature (T) and length of storage (LOS) on emissions using linear mixed effects models. Results showed that the average nitrogen (N) loss by NH3 volatilization from slurry storage was 12.5% of total nitrogen (TN), while the loss by N2O emissions only accounted for 0.05–0.39% of slurry TN. The NH3–N losses were highly related to slurry pH, lowering slurry pH leading to significant decrease of emissions. Temperature also affected NH3–N losses, with higher losses from slurry storage under warm conditions than cold conditions. No significant relationship was observed between NH3–N losses and slurry TS contents within a range from 21–169 g kg−1. The losses of N2O–N from dairy slurry storage were less affected by slurry pH, TS contents and temperature. The carbon (C) loss as CH4 emissions varied from 0.01–17.2% of total carbon (TC). Emissions of CH4–C presented a significant positive relationship with temperature, a negative relationship with slurry TS contents and no significant relationship with slurry pH ranging from 6.6–8.6. Length of storage (more than 30 days) had no significant influence on cumulative gas emissions from slurry storage. This study provides new emission factors of NH3, N2O and CH4 in the percentage of TN or TC from dairy slurry storage. Our results indicate the potential interactive effects of slurry characteristics and storage conditions on gaseous emissions from slurry storage. Farm-scale measurements are needed to accurately estimate nutrient losses from liquid manure storage.

Organic amendments are used to improve soil fertility and maintain agricultural fields in a productive state. Despite these benefits, the use of organic amendments is limited in many developing countries. The overall objective of this thesis is therefore to provide a better understanding of current waste management practices in developing countries and ensure sustainable crop production via the biotransformation of urban waste into a high-quality soil amendment. First, I aimed at determining the causes for the limited use of organic amendments in small-scale urban farming systems. I interviewed 220 urban farmers in Ethiopia and found that competition for agricultural waste between fuel, feed and soil amendment is a major cause for the limited use of organic amendments. I demonstrated that allocation of agricultural waste for soil amendment is linked with farmers’ livelihood strategies. I also studied variation in compost demand among different farmer groups, and the socio-economic variables which explained these variations. Gaseous losses of ammonia and greenhouse gas (GHG) emissions occur during composting of nitrogen-rich urban waste. Several technologies could reduce these losses. However, these technologies are inadequate to fit within the broader farming systems because they are expensive. The second aim of this thesis was to develop low-cost methods to mitigate N losses and GHG emissions from composting, while retaining its fertilising value. Composting by earthworms (vermicomposting) is proposed as a low-cost strategy for minimising N losses and GHG emissions. Using a wide range of substrate qualities (C:N ratio, labile C sources) and other factors (earthworm density, amount of input, and moisture), I showed that vermicomposting reduced N losses and GHG emissions compared with traditional thermophilic composting, but the magnitude of the earthworm effect varied between substrates. Earthworms also change the quantity and composition of dissolved organic carbon during composting. Another low-cost strategy is to delay the addition of N-rich substrates during composting. I demonstrated that addition of nitrogen-rich substrate after the thermophilic phase reduced N losses. Delayed addition of N-rich substrates increased N2O emissions, but reduced CH4 emissions. Delayed addition resulted in compost that was as stable and effective at completely eradicating weed seeds as traditional composting. In conclusion, urban waste compost should be considered as alternative source for soil amendment, particularly in developing countries with competition for agricultural waste. Technologies such as vermicomposting and delayed addition of N-rich substrate are recommended to increase or maintain the nitrogen content of compost, reduce N losses and mitigate GHG emissions.

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.