Article

Greenhouse gas emissions from dairy manure management: A review of field-based studies

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Abstract

Livestock manure management accounts for almost 10% of greenhouse gas emissions from agriculture globally, and contributes an equal proportion to the US methane emission inventory. Current emissions inventories use emissions factors determined from small-scale laboratory experiments that have not been compared to field-scale measurements. We compiled published data on field-scale measurements of greenhouse gas emissions from working and research dairies and compared these to rates predicted by the IPCC Tier 2 modeling approach. Anaerobic lagoons were the largest source of methane (368 ± 193 kg CH4 hd−1 y−1), more than three times that from enteric fermentation (~100 kg CH4 hd−1 y−1). Corrals and solid manure piles were large sources of nitrous oxide (1.5 ± 0.8 and 1.1 ± 0.7 kg N2O hd−1 y−1, respectively). Nitrous oxide emissions from anaerobic lagoons (0.9 ± 0.5 kg N2O hd−1 y−1) and barns (10 ± 6 kg N2O hd−1 y−1) were unexpectedly large. Modeled methane emissions underestimated field-measurement means for most manure management practices. Modeled nitrous oxide emissions underestimated field-measurement means for anaerobic lagoons and manure piles, but overestimated emissions from slurry storage. Revised emissions factors nearly doubled slurry CH4 emissions for Europe and increased N2O emissions from solid piles and lagoons in the US by an order of magnitude. Our results suggest that current greenhouse gas emission factors generally underestimate emissions from dairy manure and highlight liquid manure systems as promising target areas for greenhouse gas mitigation.This article is protected by copyright. All rights reserved.

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... Organic waste in landfills and manure slurries is a large source of greenhouse gas emissions globally [1,2]. Manure alone accounts for 10% of global agricultural emissions [2]. ...
... Organic waste in landfills and manure slurries is a large source of greenhouse gas emissions globally [1,2]. Manure alone accounts for 10% of global agricultural emissions [2]. Diverting organic waste to composting may lower greenhouse gas emissions, but there is uncertainty regarding emissions from the composting process. ...
... This study is the first to continuously measure greenhouse gas emissions from the commercial-scale composting of manure and green waste. Three questions guided our research: (1) how do environmental and biogeochemical characteristics vary during composting?; (2) what are the whole-pile emissions of CO 2 , CH 4 , and N 2 O, and how are they related to environmental and biogeochemical variables?; and (3) what are the net lifecycle greenhouse gas emissions from composting green waste and manure?We used field experiments, laboratory assays, and lifecycle modeling to answer these questions. ...
Article
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Direct emissions from commercial-scale composting are uncertain. We used micrometeorological methods to continuously measure greenhouse gas (CO2, CH4, N2O) emissions from full composting of green waste and manure. We measured oxygen (O2), moisture, and temperature continuously inside the composting pile, and analyzed chemical and physical characteristics of the feedstock weekly as potential drivers of emissions. Temperature, moisture, and O2 all varied significantly by week. Feedstock porosity, C:N, and potential N mineralization all declined significantly over time. Potential net nitrification remained near zero throughout. CH4 and CO2 fluxes, indicators of feedstock lability, were variable, and most emissions (75% and 50% respectively) occurred during the first three weeks of composting. Total CH4 emitted was 1.7 ± 0.32 g CH4 kg⁻¹ feedstock, near the median literature value using different approaches (1.4 g CH4 kg⁻¹). N2O concentrations remained below the instrument detection. Oxygen, moisture and temperature exhibited threshold effects on CH4 emissions. Net lifecycle emissions were negative (−690 g CO2-e kg⁻¹), however, after considering avoided emissions and sinks. Managing composting piles to minimize methanogenesis—by maintaining sufficient O2 concentrations, and focusing on the first three weeks—could reduce emissions, contributing to the climate change mitigation benefit of composting.
... These measurements involve significant effort and cost, making it difficult to make measurements over long time periods and on large numbers of animals. Bottom-up measurements of manure management methane involve laboratorybased incubations and/or field observations (Owen and Silver, 2015;Pratt et al., 2015) and have similar limitations in terms of representing different animals and diets, multiple manure management strategies, locations, and conditions, and in tracking manure management emissions from production through ultimate fate. For example, sludge removal from anaerobic lagoons may occur as rarely as once every 5-10 or more years (Chastain and Henry, 2002a,b). ...
... The quantification of Y m better allows measurements from individual animals to be extrapolated to herds and larger populations consuming similar diets. Analogously, for manure management methane, the biochemical methane potential (B o ) provides an estimate of methane production per mass of manure volatile solids (IPCC, 2006;Owen and Silver, 2015;Pratt et al., 2015). Along with estimates of the amount of volatile solids excreted in manure, B o can be used to upscale experimental observations to larger herds and populations. ...
... Because methane emissions from anaerobic lagoons are estimated to be nearly twice the magnitude of those from dry systems per unit of manure input, these changes will have a large impact in nations using these systems at high rates, such as the United States (Fig. 4) and so must be taken into account in new bottom-up inventories. Recent work has also shown that these methods underestimate actual emissions for most recent types of manure management practices (Owen and Silver, 2015). Frequent reassessment of activity data and (Owen and Silver, 2015;VanderZaag et al., 2013;Wolf et al., 2017). ...
... It has always been challenging to model gas emissions from MMSs due to the variability in farming practices that affect the manure physio-chemical characteristics (Owen and Silver, 2015). Intergovernmental Panel on Climate Change (IPCC) emission factors (Tier 1, 2, and 3) are widely used to predict gas emissions; however, in some studies (Lory et al., 2010;Owen and Silver, 2015;Leytem et al., 2017) the authors argued that these models underestimate the actual gas emissions. ...
... It has always been challenging to model gas emissions from MMSs due to the variability in farming practices that affect the manure physio-chemical characteristics (Owen and Silver, 2015). Intergovernmental Panel on Climate Change (IPCC) emission factors (Tier 1, 2, and 3) are widely used to predict gas emissions; however, in some studies (Lory et al., 2010;Owen and Silver, 2015;Leytem et al., 2017) the authors argued that these models underestimate the actual gas emissions. Hence, there is a need for more research tools and models to quantify the actual farm emissions and understand the effect of changing one component of the MMSs on the overall environmental and economic performance. ...
... Several models have been used to estimate CH 4 emissions from manure storage systems, but they have a high degree of uncertainty. Owen and Silver (2015) reported that anaerobic lagoons and slurry storage systems used for managing liquid dairy manure generated 368 ± 193 and 101 ± 47 kg CH 4 per head/year, respectively, estimated using the IPCC Tier 2 method. The reported CH 4 emissions from liquid dairy manure storage systems by USEPA and IPCC methodologies underestimate actual emissions by up to 130% (Lory et al., 2010;Balde et al., 2016;Leytem et al., 2017). ...
Article
Global dairy and swine production growth has increased significantly over the past decades, resulting in higher manure generation in certain areas and environmental concerns. Therefore, manure management is an essential focus for farmers and environmental regulators. Systematic selection of manure management practices can provide environmental benefits, but accounting for local constraints, economics and farming practices are significant challenges. All these factors drive the selection of appropriate manure management systems (MMSs). MMSs are highly varied for their design, partly due to individual farm settings, geography, and the end-use applications of manure. However, the benefits of technological advancements in MMSs provide higher manure treatment efficiency and co-production of value-added products such as recycled water, fiber, sand bedding, and nutrient-rich bio-solids, among others. To achieve higher environmental benefits, advanced manure treatment technologies have to be implemented, which comes with additional costs. So, there is a tradeoff between environmental benefits and cost. With the above prospects, this article reviews: 1) the different treatment technologies used in dairy and swine farms, 2) the life cycle assessment (LCA) method's importance in evaluating various treatment technologies for better environmental returns, and 3) decision support tools (DST) and their significance in MMSs prioritization. We found considerable heterogeneity in the available datasets, mainly on crucial parameters such as water consumption, types and amount of bedding materials, manure removal frequency, manure treatment technologies, and the extent of resource recovery. Thus, suitable environmental impact assessment inventory models are needed to evaluate a more comprehensive range of treatment technologies in MMSs, representing the spatial and farming system heterogeneities. There is also a need for user-friendly DST with adjustable inputs for the functional components of MMSs and evaluation criteria, which can rapidly evaluate the techno-economic feasibility of alternative systems.
... 2−4 Dairy feedlots in particular present a significant nutrient recycling and GHG mitigation opportunity due to their large stocking densities, high rate of manure production, and spatial decoupling of livestock from feed production. 5,6 Optimizing the treatment and reuse of dairy manure could help prevent nutrient loss while substantially reducing CH 4 emissions. This is especially relevant in dairy-intensive regions such as California, where dairy manure accounts for 25% of total CH 4 emissions. ...
... CH 4 reductions for anaerobic digestion and biocharcomposting are relative to a baseline system similar to the model in Owen and Silver in which dairy manure from mature and lactating cows is separated into a solid fraction, which is stockpiled, and a liquid fraction, which is stored in an anaerobic lagoon. 5 We assume a 50% solid separation rate, which is the average efficiency of the four solid−liquid separation technologies reviewed in Hjorth et al. 61 We do not consider any manure managed from heifers or calves because manure from immature and nonmilking cows is typically managed through alternative methods such as daily spread or dry lot systems that yield little CH 4 , and according to an analysis by Marklein et al., account for less than 2% of total dairy CH 4 emissions. 9 Current progress on SB 1383, which we use as a baseline in our model, is based on a recent CARB report that estimates that by 2022, the state will have reduced dairy CH 4 emissions by 3.5 MMT and will have 130 anaerobic digestors operating. ...
... 58 Assumptions made about the proportion of manure in liquid and solid systems are also a source of uncertainty as this ratio can vary greatly depending on the region. 5 Other estimates of global livestock manure CH 4 mitigation are also highly variable and depend largely on model assumptions. For example, CH 4 The EPA estimates a manure CH 4 reduction potential for the U.S. dairy industry of 1.64 Tg CH 4 yr −1 , which is larger than some of the estimates for global livestock manure mitigation. ...
Article
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Livestock are the largest source of anthropogenic methane (CH4) emissions, and in intensive dairy systems, manure management can contribute half of livestock CH4. Recent policies such as California's short-lived climate pollutant reduction law (SB 1383) and the Global Methane Pledge call for cuts to livestock CH4 by 2030. However, investments in CH4 reduction strategies are primarily aimed at liquid dairy manure, whereas stockpiled solids remain a large source of CH4. Here, we measure the CH4 and net greenhouse gas reduction potential of dairy manure biochar-composting, a novel manure management strategy, through a composting experiment and life-cycle analysis. We found that biochar-composting reduces CH4 by 79%, compared to composting without biochar. In addition to reducing CH4 during composting, we show that the added climate benefit from biochar production and application contributes to a substantially reduced life-cycle global warming potential for biochar-composting: -535 kg CO2e Mg-1 manure compared to -194 kg CO2e Mg-1 for composting and 102 kg CO2e Mg-1 for stockpiling. If biochar-composting replaces manure stockpiling and complements anaerobic digestion, California could meet SB 1383 with 132 less digesters. When scaled up globally, biochar-composting could mitigate 1.59 Tg CH4 yr-1 while doubling the climate change mitigation potential from dairy manure management.
... On dairy farms, for example, there are several areas which are potential sources of GHG. In fact, and according to a review by Owen and Silver [7], anaerobic lagoons are sources of CH 4 and N 2 O that exceed direct CH 4 emissions from dairy cows. ...
... However, to compare treatments and production cycles, some considerations for GHG accounting must also be taken into account. On the one hand, the reuse of DE can mitigate the environmental impact of intensive dairy farms by reducing the liquid effluent's retention time, which greatly affects the amount of CH 4 produced [7]. Considering the VS content of the DE used and the application rate, 256 kg VS were removed from the dairy farm to fertigate a hectare of maize. ...
Article
Full-text available
The reuse of effluents from intensive dairy farms combined with localized irrigation techniques (fertigation) has become a promising alternative to increase crop productivity while reducing the environmental impact of waste accumulation and industrial fertilizers production. Currently, the reuse of dairy effluents through fertigation by subsurface drip irrigation (SDI) systems is of vital importance for arid regions but it has been poorly studied. The present study aimed to assess the greenhouse gas (GHG) emissions, soil properties, and crop yield of a maize crop fertigated with either treated dairy effluent or dissolved granulated urea applied through an SDI system at a normalized N application rate of 200 kg N ha−1. Fertilizer application was divided into six fertigation events. GHG fluxes were measured during fertigation (62-day) using static chambers. Soil properties were measured previous to fertilizer applications and at the harvest coinciding with crop yield estimation. A slight increase in soil organic matter was observed in both treatments for the 20–60 cm soil depth. Both treatments also showed similar maize yields, but the dairy effluent increased net GHG emissions more than urea during the fertigation period. Nevertheless, the net GHG emissions from the dairy effluent were lower than the theoretical CO2eq emission that would have been emitted during urea manufacturing or the longer storage of the effluent if it had not been used, showing the need for life-cycle assessments. Local-specific emission factors for N2O were determined (0.07%), which were substantially lower than the default value (0.5%) of IPCC 2019. Thus, the subsurface drip irrigation systems can lead to low GHG emissions, although further studies are needed.
... Cela change les dynamiques de l'azote dans le sol, ce qui peut influer sur les émissions de N2O (Brozyna et al., 2013). Ainsi, Möller and Stinner (2009) (Chadwick et al., 2011;Kupper et al., 2020;Vigan et al., 2019;Walling et Vaneeckhaute, 2020b Owen and Silver, 2015). Des émissions de N2O et de N2 sont également possibles, même si elles ne sont pas toujours détectées (Clemens et al., 2006;Rodhe et al., 2015). ...
... Des émissions de N2O et de N2 sont également possibles, même si elles ne sont pas toujours détectées (Clemens et al., 2006;Rodhe et al., 2015). Les PRO solides (fumiers, digestats solides) sont soumis à des émissions de CO2, NH3, N2O et N2, et dans une moindre mesure aux émissions de CH4 Owen and Silver, 2015 (Clemens et al., 2006;Kupper et al., 2020). Une couverture peut également diminuer les émissions de CH4, mais l'efficacité est moins prononcée que pour le NH3 (Clemens et al., 2006;Kupper et al., 2020;Rodhe et al., 2015). ...
Thesis
La méthanisation agricole des effluents animaux est une pratique en fort développement en France. Elle produit de l’énergie renouvelable (biogaz). La valorisation des digestats au champ, comme celle des effluents non méthanisés, permet le retour au sol de nutriments et de matière organique, ce qui diminue le besoin en engrais minéraux et entretient les stocks de C des sols. Le traitement et l’épandage de ces produits peut aussi induire l’émission de gaz à effet de serre et de contaminants. La méthanisation agricole influence ces impacts : pour les maitriser, il faut comprendre comment la digestion des effluents avec des déchets importés modifie les cycles du C et du N à l’échelle de la ferme. Cette question a été traitée en s’appuyant sur un cas d’étude à l’INRAE de Nouzilly (Centre – Val de Loire) : une exploitation agricole avec un méthaniseur traitant les effluents de son élevage bovin et divers déchets organiques. Lors de l’essai au champ MétaMétha, nous avons comparé les flux d’azote au cours d’une rotation culturale fertilisée avec des engrais minéraux, des lisiers et fumiers bovins, ou des digestats issus de ces effluents. Les digestats se substituent bien aux engrais minéraux, mais ils sont sensibles à la volatilisation d’ammoniac (NH3). Les vers de terre peuvent être négativement impactés juste après l’épandage de digestat ou de lisier, mais les effets sont similairement positifs après 2 ans d’apports de matière organique. Nous avons ensuite évalué les modèles STICS et SYS-Metha pour simuler respectivement l’essai au champ et le traitement des digestats. Ces modèles ont été couplés pour simuler les flux de C et N à l’échelle de la ferme. Avec de forts imports de déchets, la méthanisation favorise la substitution des engrais minéraux, le stockage de C dans les sols, mais aussi les émissions de NH3. Ce travail permet de mieux évaluer les conséquences de l’introduction d’un méthaniseur dans une exploitation agricole et ainsi d’optimiser la filière.
... We calculated the mean and standard error for VS production for each of these two populations. We estimated the uncertainty of the MCFs using data reported by Owen and Silver (Owen and Silver, 2014). ...
... Method M3 is also very sensitive to the fraction of manure allocated to bedding (12.3%). Our data on MCF for lagoons is only based on 9 observational studies from outside California (Owen and Silver, 2014), so more measurements are needed to reduce this uncertainty. Further, there is little information on the amount of manure used for bedding. ...
Preprint
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Dairies emit roughly half of total methane (CH4) emissions in California, generating CH4 from both enteric fermentation by ruminant gut microbes and anaerobic decomposition of manure. Representation of these emission processes is essential for management and mitigation of CH4 emissions, and is typically done using standardized emission factors applied at large spatial scales (e.g., state level). However, CH4-emitting activities and management decisions vary across facilities, and current inventories do not have sufficiently high spatial resolution to capture changes at this scale. Here, we develop a spatially-explicit database of dairies in California, with information from operating permits and California-specific reports detailing herd demographics and manure management at the facility scale. We calculated manure management and enteric fermentation CH4 emissions using two previously published bottom-up approaches and a new farm-specific calculation developed in this work. We also estimate the effect of mitigation strategies – the use of mechanical separators and installation of anaerobic digesters – on CH4 emissions. We predict that implementation of digesters at the 109 dairies that are existing or planned in California will reduce manure CH4 emissions from those facilities by an average of 35 %, and total state CH4 emissions by 6 % (or ~ 47.3 Gg CH4/yr). In addition to serving as a planning tool for mitigation, this database is useful as a prior for atmospheric observation-based emissions estimates, attribution of emissions to a specific facility, and to validate CH4 emissions reductions from management changes. Raster files of the datasets and associated metadata are available from the Oak Ridge National Laboratory Distributed Active Archive Center for Biogeochemical Dynamics (ORNL DAAC; Marklein et al., 2020; https://doi.org/10.3334/ORNLDAAC/1814).
... Globally, livestock manure management is responsible for 7-8% of total agricultural emissions (5.0-5.8 Gt CO 2 e per year, Smith et al., 2014;Owen and Silver, 2014). Enteric fermentation is responsible for approximately 2 Gt CO 2 e annually (Smith et al., 2014). ...
... Emission factors for CH 4 from manure management differ by cattle subcategory (Table 4). This can be caused by various factors including digestion efficiency of the animals and the type of excreted organic matter (Owen and Silver, 2014;Appuhamy et al., 2017;Font-Palma, 2019). The factors are similar to the estimates of DEA (2016) for drylot and pasture, range and paddock management systems. ...
Article
Livestock is a major producer of agricultural greenhouse gas emissions in South Africa. Cattle methane (CH4) from enteric fermentation is the main source of the emissions. However, due to shortage of information to guide agricultural mitigation plans in the country, the main objective of this study is to investigate causal factors of the emissions from cattle in all nine national provinces. This study calculates provincial CH4 emission factors and factors (i.e. nitrogen excretion rate and average annual nitrogen excretion per animal) required for nitrous oxide (N2O) emissions from cattle manure management. The study further uses these factors and other values obtained from the literature to calculate cattle CH4 emissions from enteric fermentation and manure management. It also provides similar N2O emissions from manure management as well as urine and dung deposited on the pasture, range and paddock. The emissions are calculated for each cattle type: commercial dairy, commercial beef, subsistence and feedlot cattle. Cattle in South Africa produced a total of 35.37 million tonnes (Mt) of carbon dioxide equivalent (CO2e) emissions in 2019, inclusive of emissions from pasture, range and paddock. Methane from enteric fermentation accounts for 64.54% of the total emissions followed by emissions from pasture, range and paddock (27.66%). Manure management contributes 4.34% of N2O to the total emissions while this source also produces 3.45% of CH4 emissions. Commercial beef is responsible for 50.21% of the total emissions, followed by subsistence beef (36.72%), commercial dairy (10.52%) and feedlot cattle (2.52%). The Eastern Cape province is the highest producer of cattle emissions with 8.66 Mt CO2e, a quarter of the emissions. It is followed by KwaZulu-Natal (7.14 Mt CO2e, 20%) and the Free State (5.65 Mt CO2e, 16%). Gauteng province is responsible for the lowest producer of the emissions with 0.71 Mt CO2e (2%) of the total. South Africa’s emission factors are higher than values for Africa, indicating importance of developing national factors to avoid uncertainties in emissions. As a result of national landscape and environmental conditions, the eastern provinces of the country are major sources of cattle emissions in the country.
... We calculated the mean and standard error for VS production for each of these two populations. We estimated the uncertainty of the MCFs using data reported by Owen and Silver (Owen and Silver, 2014). We estimated the uncertainty of B o , the theoretical maximum methane production, using data from a meta-analysis (Miranda et al., 2016). ...
... Here, all three of our methods are most sensitive to the lagoon MCF (45.0 %-80.2 %), followed by n cows (7.2 %-15.3 %), except for M3, which is sensitive to the fraction of manure allocated to bedding (41.5 %) (Table 4). Our data on MCF for lagoons are only based on nine observational studies from outside California (Owen and Silver, 2014), so more measurements are needed to reduce this uncertainty. Further, there is little information on the amount of manure used for bedding. ...
Article
Full-text available
Dairies emit roughly half of total methane (CH4) emissions in California, generating CH4 from both enteric fermentation by ruminant gut microbes and anaerobic decomposition of manure. Representation of these emission processes is essential for management and mitigation of CH4 emissions and is typically done using standardized emission factors applied at large spatial scales (e.g., state level). However, CH4-emitting activities and management decisions vary across facilities, and current inventories do not have sufficiently high spatial resolution to capture changes at this scale. Here, we develop a spatially explicit database of dairies in California, with information from operating permits and California-specific reports detailing herd demographics and manure management at the facility scale. We calculated manure management and enteric fermentation CH4 emissions using two previously published bottom-up approaches and a new farm-specific calculation developed in this work. We also estimate the effect of mitigation strategies – the use of mechanical separators and installation of anaerobic digesters – on CH4 emissions. We predict that implementation of digesters at the 106 dairies that are existing or planned in California will reduce manure CH4 emissions from those facilities by an average of 26 % and total state CH4 emissions by 5 % (or ∼36.5 Gg CH4/yr). In addition to serving as a planning tool for mitigation, this database is useful as a prior for atmospheric observation-based emissions estimates, attribution of emissions to a specific facility, and validation of CH4 emissions reductions from management changes. Raster files of the datasets and associated metadata are available from the Oak Ridge National Laboratory Distributed Active Archive Center for Biogeochemical Dynamics (ORNL DAAC; Marklein and Hopkins, 2020; https://doi.org/10.3334/ORNLDAAC/1814).
... The review of Owen and Silver (2015) reported CH 4 emission data from lagoons and tanks of dairy systems being 2.3 and 2.7 g CH 4 m −2 h -1 , respectively. This is higher than data from farm-scale studies reported here which are 1.2 and 1.3 g CH 4 m −2 h -1 for cattle slurry stored in lagoons and tanks, respectively (Supplementary data 4). ...
... This is higher than data from farm-scale studies reported here which are 1.2 and 1.3 g CH 4 m −2 h -1 for cattle slurry stored in lagoons and tanks, respectively (Supplementary data 4). However, the data basis of Owen and Silver (2015) is smaller and measurements carried out in the warm season tend to be overrepresented. The higher CH 4 emissions from pig slurry as compared to cattle slurry are expected due to the higher methane production potential of pig slurry (Triolo et al., 2011). ...
Article
Full-text available
Storage of slurry is an important emission source for ammonia (NH3), nitrous oxide (N2O), methane (CH4), carbon dioxide (CO2) and hydrogen sulfide (H2S) from livestock production. Therefore, this study collected published emission data from stored cattle and pig slurry to determine baseline emission values and emission changes due to slurry treatment and coverage of stores. Emission data were collected from 120 papers yielding 711 records of measurements conducted at farm-, pilot- and laboratory-scale. The emission data reported in a multitude of units were standardized and compiled in a database. Descriptive statistics of the data from untreated slurry stored uncovered revealed a large variability in emissions for all gases. To determine baseline emissions, average values based on a weighting of the emission data according to the season and the duration of the emission measurements were constructed using the data from farm-scale and pilot-scale studies. Baseline emissions for cattle and pig slurry stored uncovered were calculated. When possible, it was further distinguished between storage in tanks without slurry treatment and storage in lagoons which implies solid-liquid separation and biological treatment. The baseline emissions on an area or volume basis are: for NH3: 0.12 g m⁻² h⁻¹ and 0.15 g m⁻² h⁻¹ for cattle and pig slurry stored in lagoons, and 0.08 g m⁻² h⁻¹ and 0.24 g m⁻² h⁻¹ for cattle and pig slurry stored in tanks; for N2O: 0.0003 g m⁻² h⁻¹ for cattle slurry stored in lagoons, and 0.002 g m⁻² h⁻¹ for both slurry types stored in tanks; for CH4: 0.95 g m⁻³ h⁻¹ and 3.5 g m⁻³ h⁻¹ for cattle and pig slurry stored in lagoons, and 0.58 g m⁻³ h⁻¹ and 0.68 g m⁻³ h⁻¹ for cattle and pig slurry stored in tanks; for CO2: 6.6 g m⁻² h⁻¹ and 0.3 g m⁻² h⁻¹ for cattle and pig slurry stored in lagoons, and 8.0 g m⁻² h⁻¹ for both slurry types stored in tanks; for H2S: 0.04 g m⁻² h⁻¹ and 0.01 g m⁻² h⁻¹ for cattle and pig slurry stored in lagoons. Related to total ammoniacal nitrogen (TAN), baseline emissions for tanks are 16% and 15% of TAN for cattle and pig slurry, respectively. Emissions of N2O and CH4 relative to nitrogen (N) and volatile solids (VS) are 0.13% of N and 0.10% of N and 2.9% of VS and 4.7% of VS for cattle and pig slurry, respectively. Total greenhouse gas emissions from slurry stores are dominated by CH4. The records on slurry treatment using acidification show a reduction of NH3 and CH4 emissions during storage while an increase occurs for N2O and a minor change for CO2 as compared to untreated slurry. Solid-liquid separation causes higher losses for NH3 and a reduction in CH4, N2O and CO2 emissions. Anaerobically digested slurry shows higher emissions during storage for NH3 while losses tend to be lower for CH4 and little changes occur for N2O and CO2 compared to untreated slurry. All cover types are found to be efficient for emission mitigation of NH3 from stores. The N2O emissions increase in many cases due to coverage. Lower CH4 emissions occur for impermeable covers as compared to uncovered slurry storage while for permeable covers the effect is unclear or emissions tend to increase. Limited and inconsistent data regarding emission changes with covering stores are available for CO2 and H2S. The compiled data provide a basis for improving emission inventories and highlight the need for further research to reduce uncertainty and fill data gaps regarding emissions from slurry storage.
... The growing season N 2 O emissions dominated the total annual emissions and accounted for 95%, 76% and 66% of annual fluxes at the inside and outside sheepfolds and summer cattle shed, respectively. CO 2 emissions from livestock are not considered as a net contributor to GHG emissions (IPCC, 2006;Owen & Silver, 2015). Therefore, the cumulative annual GHG emissions were estimated in CO 2 equivalents using only CH 4 and N 2 O emissions from both sheepfolds and summer cattle shed. ...
... The N 2 O emission rate of 0.15 g N 2 O-N cattle −1 day −1 in our study was three times lower compared to 0.48 g N 2 O cow −1 day −1 from dairy cattle in a chamber in California (Hamilton et al., 2010). The CO 2 efflux (142 kg CO 2 year −1 cattle −1 ) was within the range of 25-250 kg CO 2 year −1 herd −1 from barn floor reported by Owen and Silver (2015). Our data of CH 4 and N 2 O emissions were much higher than 0.02 g CH 4 cow −1 day −1 and 0.006 g N 2 O-N cow −1 day −1 from the dairy hardstandings in the UK (Ellis et al., 2001). ...
Article
Livestock sheds are local and regional hotspots of greenhouse gases (GHG) emissions, but only very few studies analyze the intensities of GHG emissions from this source. The objective of this study was to quantify annual CH4, CO2 and N2O emissions from inside and outside of sheepfolds and summer cattle sheds in a typical agro-pastoral ecotone using static chamber technique. Both sheepfolds and cattle shed functioned as huge net sources of CH4 and N2O at annual scale. Animal presence increased CH4, CO2 and N2O effluxes for up to 1100 times compared to the animal sheds without animals. N2O emissions boosted for 160-280% during and after rainfall and spring-thaw events. The CH4 and CO2 fluxes increased exponentially with feces temperature for the outside sheepfold and summer cattle shed. The annual GHG emissions from both sheepfolds and summer cattle shed were 56 t CO2 equivalents ha⁻¹, of which N2O contributed to 94%. Sheepfold dominated the total GHG emissions from animal sheds and accounted for 83% of the annual GHG flux. Annual emission on a per animal basis was 15, 0.2 and 28 kg CO2 eq yr⁻¹ sheep⁻¹ and 26, 10 and 140 kg CO2 eq yr⁻¹ cattle⁻¹ for N2O, CH4 and CO2, respectively. The annual N2O emissions from animal sheds were 70-250 times larger than nearby grassland soils, which were also net sink for atmospheric CH4. Concluding, animal sheds are very intensive local hotspots of GHG emissions which should be considered at the local and regional scales.
... Furthermore, within the GHG emission from agriculture, over onethird comes from livestock production, representing around 99% of the agricultural methane emissions (Chianese et al., 2009;EPA, 2020). Also, manure contributes over 10% of the GHG emitted from agriculture (EPA, 2020;Owen & Silver, 2015). Within the methane emission from manure across all livestock species, manure from beef cattle accounts for ~ 15% of these emissions (Table 1.1). ...
... Another study (Owen & Silver, 2015) states that because mechanistic and empirical models are based on laboratory-scale measurements, they tend to underestimate the potential emissions of methane in a full-scale basis. Owen and Silver (2015) reported an EF for solid manure of 13 ± 11 kg CH4 hd -1 yr -1 based on farm-level measurements and a predicted value of 22 kg CH4 hd -1 yr -1 , 4-7 folds higher than the values reported in this study. ...
Article
The emission of methane from livestock production contributes to climate change. Cattle manure accounts for one-third of the total methane emission over the lifecycle of beef and dairy production and represents an opportunity to lower the environmental footprint of the beef industry. While models have been developed to estimate methane emissions from manure under certain types of manure storage methods, there is a lack of a user-friendly interface that agricultural or environmental engineers can use to estimate the methane emission from manure for specific regions. Therefore, the goal of this study was to build an interface to estimate methane emissions factors (EFs) and overall methane emissions for the beef cattle manure in Nebraska under various manure management scenarios. The Tier 2 model developed by the Intergovernmental Panel on Climate Change was adopted in the study. Besides, a typical scenario of beef cattle production in Nebraska was adopted in the study, where animals grow an average weight of 318 kg hd-1 to 635 kg hd-1 during the 200 days in feedlots. The interface developed in this study encompasses four major manure management systems: solid storage, uncovered anaerobic lagoon, composting static pile, and daily spread. A range of temperatures, from 10 to 28ºC, were considered in the study. For solid storage, the EFs were calculated to range from 0.98 to 3.05 kg CH4 hd-1 yr-1 and the overall emissions from 5.89 to 18.29 Gg CH4 yr-1 for the 2.82 million heads of beef cattle in Nebraska in the Year 2021. Higher EFs were found for liquid storage, averaging at 37.69 and 45.68 kg CH4 hd-1 yr-1 in winter and summer, respectively. Furthermore, overall emissions can reach 226 Gg CH4 yr-1 on a winter day and 274 Gg CH4 yr-1 in the summer. After analyzing the methane emissions from both solid and liquid storage, it is noticeable that moisture content plays an important role in methane production. The methane production trend falls when the moisture content decreases, confirming that a reduction of the water content of manure could potentially lower CH4 emissions from manure. Thus, this observation opens the possibility to investigate the feasibility of reducing water in manure as a mitigation measure for methane emission. Advisor: Xu Li
... The amount of manure N produced each year was even higher than the production of chemical fertilizer N in 2000 and 2050 (Bouwman et al., 2014). According to Owen and Silver (2015), manure management accounts for 10 % of greenhouse gas emissions from agriculture worldwide. Therefore, this substantial quantity of manure represents a high environmental risk for nitrogen pollution such as nitrate leaching, ammonium volatilization, and nitrous oxide and nitric oxide emissions. ...
Article
Intensive manure application is a significant source for environmental nitrogen fluxes. In this study, we evaluated the effect of intensive manure management on nitrogen(N) loading and recommended the critical livestock density for the typical paddy rice and corn cropping systems in a dairy farming watershed using a calibrated DNDC model. The results indicated that a significant amount of N was lost as N2O emission and NO3⁻-N leaching under current intensive manure application. As the number of dairy cattle increased, soil N2O emissions and NO3⁻-N leaching increased with a rate of 2.11 kg N LU⁻¹ yr⁻¹ and 39.7 kg N LU⁻¹ yr⁻¹, respectively. Changing manure to chemical fertilizer, NO3⁻-N leaching was trend to increased. If decreasing fertilizer rate too low, crop N decreased and the soil N was significantly deficit. Integrated all the analysis, we recommended that critical N application rate was approximately 150–300 kg N ha⁻¹ yr⁻¹ for corn system and 100–250 kg N ha⁻¹ yr⁻¹ for paddy rice system, respectively. The critical livestock density in these cropping systems is 0.7–3.0 LU ha⁻¹ yr⁻¹ for dairy cattle manure using. Based on these recommendations, the crop N use efficiency(NUE) could increase from 17 % to 65 % for corn cropping and from 59 % to 75 % for paddy rice cropping. To mitigation the significant environmental nitrogen, the current livestock densities need to decrease by 40–60 % in the studied region or the major crop system needs to be changed from one season rice to double rotation cropping system.
... The manure management system (MMS)-the entire system of various components (handling, storage, and application), which may or may not be interchangeable-involves a balance of these aforementioned tradeoffs. For example, liquid lagoon systems use large amounts of water, and may store manure anaerobically, which can increase greenhouse gas emissions [11][12][13]. However, the storage capacity of a lagoon ensures that farmers can apply nutrients when agronomically and climatically appropriate. ...
Article
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Among one of the key challenges in dairy production is the management of manure in a way that is beneficial for agricultural production, with minimal environmental and public health impacts. Manure management systems (MMS)—the entire system of handling, storage, and application of manure—are diverse in countries with developed dairy industries such as the United States, enabled by a number of different technologies. The ways in which dairy farmers manage manure is driven by varying tradeoffs, including economic, social, and environmental; however, existing research has not examined the relationships between components of MMS. Here we use data from the National Animal Health Monitoring System’s Dairy 2014 study to explore the ways in which manure handling, storage, and application are related, using a series of logistic regression models and network associations. We found significant associations between how manure is handled, stored, and applied, especially driven by the consistency of manure. For solid manure, we found highly heterogeneous systems, where farmers may have a suite of alternative manure management strategies available to them, and substitution is viable. Conversely, farms using liquid manure systems have very few substitutes in their MMS, suggesting greater investment in certain infrastructures, which are not easily changed. Such findings have important implications for shifting farmers towards management practices with minimal environmental and public health impacts, demonstrating that not all farm systems are easily changed. We highlight these results in light of current policies, which may not fully capture the relationships across the MMS, and suggest that greater financing may be necessary to shift MMS on some farms. Furthermore, we suggest that different MMS have varying tradeoffs across environmental, social, and economic aspects, which demonstrates that MMS are highly individualized to a given farm’s goals and priorities.
... By the end of the first decade of this century, the dairy sector contributed nearly 2% of the United States greenhouse gas (GHG) emissions (Thoma et al., 2013). The three major GHG emitted from dairy production systems are carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O; Owen and Silver, 2015). Enteric fermentation (cow emission), the emissions during collection, processing and storage of manure and field emissions associated with feed production are the three main sources of on-farm GHGs contributing roughly 72% of the milk carbon footprint in the United States (Thoma et al., 2013). ...
Article
On-farm greenhouse gas (GHG) emissions from cows, manure, and fields (to produce feed) comprise more than 72% of the United States milk carbon footprint. Recent studies examined the impact of dietary strategies on enteric methane emissions, however, tradeoffs between enteric methane and manure related GHG emissions have not been determined. Thus, the objective of this study was to determine the carry-over effects of dairy cow breed and diet on manure composition and manure GHG emissions during storage and after field application. The GHG emissions were measured using static chamber method for 50 days (d) during storage and 50-d after field application (30-d in the fall and 20-d in the following spring) of manure collected from four Holstein and four Jersey cows fed either alfalfa silage or corn silage based diets containing low forage neutral detergent fiber (FNDF) or high FNDF. None of the interactions among treatment factors were significant (P > 0.10). Manure composition was affected by both FNDF level and FNDF source but not cow breed. For example, manure pH was lower for low FNDF-fed than high FNDF-fed cows and concentrations of organic matter, total carbon, and neutral detergent fiber were greater in manure of corn silage-fed than alfalfa silage-fed cows. Except for starch (which was in low concentration), all the measured manure characteristics changed during the storage period. Treatments did not affect either hourly CO2, methane and nitrous oxide emissions, nor cumulative emissions (over 50-d of storage or over 50-d after land application), except for a tendency (P < 0.10) to emit 22% lower manure CO2 by high FNDF-fed cows than low FNDF-fed cows. Cumulative methane and nitrous oxide emissions were respectively 25 times greater and 19 times lower during the 50-d manure storage period than the subsequent 50-d after field application. Cumulative field nitrous oxide emission was 17 times greater during spring than fall. Depending on mode of expression (emissions per kg manure or per kg milk or per cow basis), manure of low FNDF-fed cows tended to emit 51 to 72% greater 100-d (combined storage and field) non-CO2 GHG emissions than high FNDF-fed cows. However, in this study, neither cow breed nor FNDF source affected the 100-d combined non-CO2 GHG emissions.
... For example, Baldini et al. (2018) reported a 21% under-estimation of GHG emissions when using Intergovernmental Panel on Climate Change (IPCC) based emission factors compared to empirical data. Hence, the site-specific inventory data including direct measurement of emission factors rather than estimation using IPPC equations might capture the differences in regional characteristics or farm management practices resulting in accurate LCA results (Owen and Silver, 2015). ...
Presentation
We determined the partial carbon footprint (CF) of milk for 4 diets fed to 2 breed using measured enteric methane and greenhouse gas emissions during manure storage and after field application. Emissions and animal performances were collected in companion studies with diets containing forage neutral detergent fiber at 2 levels (NDF; 19 and 24% of dry matter, referred as low forage and high forage diets, respectively) and from 2 sources [70:30 or 30:70 ratio of alfalfa silage (AS) NDF and corn silage (CS) NDF]. Measured emissions were incorporated in a modeled Wisconsin dairy farm of 117 ha of cropland with a dairy herd consisting of 122 lactating cows (all primiparous), 22 dry cows, and 119 heifers. We assumed that manure was field-applied according to a nutrient management plan, and cropland was used to produce AS, CS and corn grains fed to the cows. Purchased inputs included other concentrate feed to balance rations and chemical fertilizers necessary to fertilize the crops as recommended. The cradle-to-gate life cycle assessment was performed with SimaPro using fat- and protein-corrected milk (FPCM) as the functional unit. Emissions were allocated between milk and meat using either economic or mass allocation. Low forage-fed cows had 11% greater CF than high forage-fed cows (1.57 vs. 1.42 kg CO2-e/kg FPCM) most likely due to the increase in both DMI and milk production when cows were fed with greater content of highly digestible soyhull in the low-forage compared with the high-forage diets. Forage sources did not influence CF (1.50 kg CO2-e/kg FPCM). The CF for Holsteins was 5% greater than for Jerseys (1.55 vs. 1.48 kg CO2-e/kg FPCM). Overall, CF was 1.5 kg CO2-e/kg FPCM when using economic allocation, but 1.42 kg CO2-e/kg FPCM when using mass allocation. Under this study conditions, differences in enteric emission intensity across diets were minimal but differences in emission intensity became substantial when assessed by combining the effects of the cow, the manure, the on-farm crop rotation, and the purchased feed, highlighting the need for an integrated approach to assess the diet effects on milk CF.
... Likewise, several models have been used to estimate the CH 4 emissions from manure storage systems, which unfortunately possess a higher degree of uncertainties. For example, using the IPCC Tier 2 method, for the management of liquid manure in anaerobic lagoons and slurry storage systems, the reported CH 4 emissions were in the range of 368 ± 193 and 101 ± 47 kg CH 4 per head/year, respectively (Owen and Silver, 2015). ...
Article
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The contribution of greenhouse gas (GHG) emissions from ruminant production systems varies between countries and between regions within individual countries. The appropriate quantification of GHG emissions, specifically methane (CH4), has raised questions about the correct reporting of GHG inventories and, perhaps more importantly, how best to mitigate CH4 emissions. This review documents existing methods and methodologies to measure and estimate CH4 emissions from ruminant animals and the manure produced therein over various scales and conditions. Measurements of CH4 have frequently been conducted in research settings using classical methodologies developed for bioenergetic purposes, such as gas exchange techniques (respiration chambers, headboxes). While very precise, these techniques are limited to research settings as they are expensive, labor-intensive, and applicable only to a few animals. Head-stalls, such as the GreenFeed system, have been used to measure expired CH4 for individual animals housed alone or in groups in confinement or grazing. This technique requires frequent animal visitation over the diurnal measurement period and an adequate number of collection days. The tracer gas technique can be used to measure CH4 from individual animals housed outdoors, as there is a need to ensure low background concentrations. Micrometeorological techniques (e.g., open-path lasers) can measure CH4 emissions over larger areas and many animals, but limitations exist, including the need to measure over more extended periods. Measurement of CH4 emissions from manure depends on the type of storage, animal housing, CH4 concentration inside and outside the boundaries of the area of interest, and ventilation rate, which is likely the variable that contributes the greatest to measurement uncertainty. For large-scale areas, aircraft, drones, and satellites have been used in association with the tracer flux method, inverse modeling, imagery, and lidar, but research is lagging in validating these methods. Bottom-up approaches to estimating CH4 emissions rely on empirical or mechanistic modeling to quantify the contribution of individual sources (enteric and manure). In contrast, top-down approaches estimate the amount of CH4 in the atmosphere using spatial and temporal models to account for transportation from an emitter to an observation point. While these two estimation approaches rarely agree, they help identify knowledge gaps and research requirements in practice.
... plant N demand. climate and soil variables) influencing direct soil emissions [5]; (ii) the N excreted by livestock animals and treated in the different steps of the manure management continuum (generation, storage, treatment and land application) using emission factors based on manure composition, manure production rates, biogeochemical reaction rates, temperature, pH, and moisture content [6,7]; and (iii) the mass of agricultural crop residues burnt on-site taking into account the fractions removed from burning, i.e. those that decayed in the field or were destined to other uses [8]. The top-down approach infers anthropogenic N 2 O emissions from the relationship between concentration growth of N 2 O as a proxy for overall emissions and known atmospheric removal rates [9]. ...
Article
Agricultural activities constitute the main N2O emission source in Argentina. Although GHG inventories have been developed at the national and provincial level, emissions have not been thus far estimated at a higher spatial resolution. We estimated the time series 2000–2012 of N2O emissions at national, provincial and district levels. National N2O emissions in 2012 amounted to 105.1 Gg (95% CI: 73.0–200.7), with manure deposited on pasture accounting for 59.8%, crop residues 24.0%, N-fertilizers use 14.3%, manure management 1.7% and agricultural waste burning 0.2%. Beef cattle excreta followed by soybean crop residues were the major sources of N2O. The time series of N2O emission estimated at district level allowed identifying the effect of the frequent displacement of crops and livestock indicative of the variability of the intensity and location of the emission sources. The observed annual variability of emissions and the identification of the main drivers indicate the convenience of using surrogate methods to estimate emissions when activity data cannot be acquired on annual basis. This type of inventory would be of interest for decision makers and stakeholders when discussing environmental policies and measures in light of the responsibility of agricultural activities occurring in the territory of their concern.
... The process of digestion produced methane as a byproduct hence contributing to its accumulation in the atmosphere. In this regard when animals are kept for long, the more they produce methane, and therefore, this should be shortened and ensure the levels of methane per production unit are minimal (Owen and Silver 2015). The three main existing options to mitigate this kind of fermentation and emissions are 1. ...
... Nitrogen fertilizers and biogas slurry liquid fertilizers from a CH 4 -generating tank increased CH 4 emission in paddy soils [31] . Changes in the conventional crop management regimes, such as alternate wetting and drying irrigation, could significantly reduce CH 4 emissions compared to continuous flooding [32] by introducing periodically aerobic conditions during rice-growing seasons [33] . ...
Article
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Stabilizing greenhouse gas (GHG) emissions from croplands as agricultural demand grows is a critical climate change mitigation strategy. Depending on management, the Agriculture, Forestry, and Other Land Use (AFOLU) sector can be both a source as well as a net sink for carbon. Currently, it contributes 25% of the global anthropogenic carbon emissions. Although India's emissions from this sector are around 8% of the total national GHG emissions, it can contribute significantly to the country's aspirations of reaching net-zero emissions by 2070. In this review, we explain the carbon footprints of the AFOLU sector in India, focusing on enteric fermentation, fertilizer and manure management, rice paddies, burning of crop residues, forest fires, shifting cultivation, and food wastage. Furthermore, using the standard autoregressive integrated moving average method, we project India's AFOLU sector emission routes for 2070 under four scenarios: business as usual (BAU) and three emission reduction levels, viz., 10%, 20%, and 40% below BAU. The article focuses on how the AFOLU sector can be leveraged proactively to reach the net-zero emission goals. Increasing forest cover, agroforestry, and other tree-based land-use systems; improving soil health through soil management, better crop residue, and livestock feed management; emission avoidance from rice ecosystems; and reducing food waste are all important strategies for lowering India's AFOLU sector carbon footprints.
... Although N losses increase with N fertilisation (VanderZaag et al., 2011;Owen and Silver, 2014), it is possible to reduce such losses by improving N fertilizer management (Alluvione et al., 2010;Ryals and Silver, 2013). For example, in terms of application timing, autumn slurry application may increase N 2 O emissions during spring due to freeze-thaw events , but spring application may also increase N 2 O due to higher rainfall and soil temperatures, which stimulate denitrification (Rochette et al., 2004;Kandel et al., 2018). ...
Article
Livestock manure is a major source of nitrogen (N) for plants, but also of ammonia (NH3) and nitrous oxide (N2O) emissions to the atmosphere, and nitrate (NO3-) leaching to groundwater. Slurry application practices targeted at reducing each of these N losses individually are relatively well known. Yet, our understanding of the potential relationships between N loss pathways is far from being complete. In this field study on grassland, we tested the effect of slurry application timing (autumn vs. winter vs. spring) and method (injection vs. broadcasting) and their interactions on N2O emissions, NH3 volatilization and NO3- leaching, as well as on plant N uptake. We found that autumn application increased NO3- leaching by 65% compared with winter and spring due to 63% higher rainfall following application. On average, autumn application reduced plant N uptake by 26%. N2O emissions after winter slurry application were 43% higher that after either spring or autumn applications. Slurry application method had no effect on NO3- leaching. Slurry injection led to 32% higher N2O emissions compared with broadcast application. Slurry injection decreased NH3 volatilization only in autumn when the soil was relatively dry before application, but not in winter or spring when the soil was wet. Changes in slurry application timing led to variations in total N losses of up to 146%, and application method of up to 19%, highlighting the great potential of slurry application practices to steer an efficient N management. Overall, autumn application should be avoided to promote more sustainable grassland production; however, if slurry must be applied in autumn, injection should be recommended to reduce NH3 volatilization.
... Livestock manure includes dung and urine [81]. Globally manure is responsible for around 7% of agricultural emissions GHGs (e.g CH 4 and N 2 O) emissions [82], [83]. It is the second source of farm GHG emissions after enteric fermentation process which emits methane (CH 4 ) [83]. ...
Article
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Agriculture sector is one of major sources of income and livelihood to many populations of Sub-Saharan Africa (SSA). Over the past years animal production has been playing a vital role not only in generating revenues to farmers but also as a source of high qualitative proteins and essential micronutrients (i.e iron, zinc and vitamins) and boosting the agricultural productivity due to its importance in farmyards organic fertilization (i.e manure). Livestock production and Milk market in SSA are dominated by smallholder dairy farming (SDF) which employ nearly 70% of all livestock farmers. Despite its positive impact on people and SSA countries’ economy, SDF has been the major fastest growing agricultural contributors of GHG emissions such as CH4, N2O and CO2 (i.e 9t CO2e per tonne of milk; the highest in the world compared to other regions) thus accelerating global warming effect. Although several articles have investigated the impacts of livestock production on climate change, to the best of our knowledge the existing literature doesn’t contain any studies that provide insight review of smallholder dairy farming’s carbon footprint (CF) in SSA. This review paper is therefore aimed at critical analysis of current knowledge in terms of CF of smallholder dairy farming in SSA and effective mitigation strategies (dietary, manure and animal management) recently proposed to reduce CH4 and N2O emissions from ruminants. SSA was selected because of rapid rise of SDF in the region therefore it is expected to rapidly increase its GHG emissions in future if no sustainable measures are taken. The critical analysis, what is known and gaps in SDF from this review will help to inform the farmers, researchers, decision and policy makers interested in GHG emissions thus to provide the next direction in research and improvement of the sector for sustainability. Capacity building for raising awareness among farmers was identified as paramount to better understand the issue and the options to mitigate emissions on-farm. As longer as adaptation and mitigation strategies become paramount on national and regional agenda, SDF will make significant contribution to economies, improved livelihood and become sustainable livestock production systems in SSA at large.
... As a consequence, stored slurry is the main source of methane emissions from pig production 4 and a significant source of methane from dairy production (20−50%) depending on climate. 5 Cost-effective strategies for mitigating CH 4 emissions from manure storage are therefore critically needed to reduce the climate impact of livestock production. ...
... Emissions of ammonia (NH 3 ) and methane (CH 4 ) from livestock production are a major environmental concern worldwide as these gases contribute to global warming and play an important role in eutrophication of ecosystems, and airborne particulate matter pollution (United States Environmental Protection Agency, 2004Stokstad, 2014). With the intensification of dairy production, dairy barns have been identified as an important source of NH 3 and CH 4 (Drewry, Choi, Powell, & Luck, 2018;Ngwabie, Jeppsson, Nimmermark, Swensson, & Gustafsson, 2009;Owen & Silver, 2015). About 20% or even more of ammoniacal nitrogen excreted in dairy housing is lost via NH 3 emission (European Environment Agency, 2016;Sommer, Webb, & Hutchings, 2019). ...
Article
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This study presents a meta-analysis of measured ammonia (NH3) and methane (CH4) emissions from dairy barns. A total of 27 peer-reviewed articles were selected to explore relationships between gas emission rates and housing system, measurement methods and environmental factors using linear mixed effect models. A large variation in measured gas emission rates from dairy buildings was observed, with 3.6–109.4 g AU⁻¹ d⁻¹ (AU refers to Animal Unit equalling 500 kg live mass) for NH3 emission and 102.1–462.2 g AU⁻¹ d⁻¹ for CH4 emission. Ammonia emissions were mainly influenced by temperature and relative humidity, with higher temperature leading to higher NH3 emission but conversely for relative humidity. There were no significant differences in NH3 emission rates among measurement techniques for ventilation rate and gas concentration. The emission of CH4 from dairy barns increased with increase of temperature but was less affected by relative humidity and wind speed. Measurement techniques for ventilation rate could significantly affect CH4 emission estimates, with higher emission measured by CO2 balance methods and inverse dispersion and lower emission when measured by anemometers. Both NH3 and CH4 emissions presented no significant difference between solid floor and slatted floor, or between flushed and scraped systems. Our results indicate that environmental factors have more pronounced effects on NH3 and CH4 emissions than housing factors. It is necessary to establish gaseous emission factors for particular climate zones. Standardised measurement methods for gas emission rates from dairy barns are needed to reduce large variability and uncertainty.
... For example, Baldini et al. (2018) reported a 21% under-estimation of GHG emissions when using Intergovernmental Panel on Climate Change (IPCC) based emission factors compared to empirical data. Hence, the site-specific inventory data including direct measurement of emission factors rather than estimation using IPPC equations might capture the differences in regional characteristics or farm management practices resulting in accurate LCA results (Owen and Silver, 2015). ...
Article
Our objective was to determine the cradle-to-farmgate carbon footprint of fat-and-protein corrected milk (FPCM) for four diets fed to two breeds using measured enteric methane and greenhouse gas emissions during manure storage and after field application. The diets were formulated as 2×2 factorial with forage neutral detergent fiber at two levels (19 and 24 % of diet dry matter referred to as low forage and high forage diets, respectively) from two sources (70:30 or 30:70 ratio of alfalfa silage and corn silage). Measured emissions were incorporated in a modeled Wisconsin dairy farm with a herd consisting of 118 lactating cows (primiparous), 22 dry cows, and 119 heifers. Emissions were allocated between milk and meat using biophysical allocation, and a sensitivity analysis was performed to determine the impact of alternative allocation methods. Overall, carbon footprint was 1.43 kg CO2-e/kg FPCM for biophysical allocation, and 1.50 and 1.60 kg CO2-e/kg FPCM for economic and no allocation (100% allocated to milk), respectively. Forage source did not influence results. However, low forage-fed cows had 10% greater carbon footprint than high forage-fed cows (1.49 vs. 1.35 kg CO2-e/kg FPCM). Assuming similar herd structure, milk carbon footprint for Holsteins was 4.4% greater than for Jerseys (1.47 vs. 1.41 kg CO2-e/kg FPCM). Accounting for differences in fertility and replacement rate increased the difference in milk carbon footprint between breeds to 10%. Under our study conditions, differences in milk carbon footprint due to enteric fermentation were minimal but the differences became substantial when combining the effects of cow (enteric CH4) and manure (CH4 and N2O) emissions. These differences were exacerbated even further when accounted for the emissions associated with on-farm feed production and purchased feed (CO2 and N2O). This study highlights the need for an integrated approach to assess the effects of dietary manipulations on milk carbon footprint.
... The California Air Resources Board (CARB) GHG inventory estimates that dairies contribute about half of statewide CH 4 emissions, with contributions from enteric fermentation by ruminant gut microbes and manure managed in anaerobic conditions. However, these estimates are based on emission factors derived from a few pilot and labscale studies conducted outside of California and thus likely not representative of California's climate and unique biogeography (Owen & Silver, 2015). Given that mitigation practices are targeted toward the biogeochemical and management processes that produce CH 4 , new tools for source apportionment and process understanding are required . ...
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Plain Language Summary Methane emissions from livestock production are an important part of the global methane budget. However, more measurements of carbon isotopes of methane are needed to help constrain the relative contribution of methane sources regionally. In this study, we measured carbon isotopes of methane at dairy farms in California, the leading dairy‐producing state in the United States. Different areas of the dairy farm had distinct methane generation processes, reflected in the isotopic signatures of methane that were emitted. Methane from manure lagoons was more enriched in the heavier of carbon’s two stable isotopes, carbon‐13, than methane from enteric fermentation across seasons at a dairy farm. Isotopic signatures of methane were comparable across seasons, particularly from manure lagoons. In addition, enteric methane from different cattle production groups had distinct isotopic signatures of methane that are likely dependent on diet composition. Isotopic signatures can also be used to apportion methane emissions from both enteric fermentation and anaerobic manure lagoons by taking samples downwind of dairy farms. This can help constrain the relative contributions from these different sources of emissions to the methane budget, as well as track the effectiveness of mitigation strategies by estimating the contribution of sources.
... Globally, the livestock sector emits ca. 5.6-7.5 Gt CO 2 -eq yr À1 (considering the livestock supply chain, Herrero et al., 2016), most of which is attributed to enteric methane (CH 4 ) from ruminants (33%), while CH 4 and nitrous oxide (N 2 O) emissions from manure management account for another 10% of global agricultural emissions Owen and Silver, 2015;Steinfeld et al., 2006). Accurate GHG emission estimates from livestock production systems and their components (animals, manure, feed crops and forages) remain scarce for sub-Saharan Africa (SSA) due to a lack of in situ studies Goopy et al., 2018;Pelster et al., 2016;Zhu et al., 2018), but they are essential for national GHG reporting and for narrowing uncertainties regarding GHG emissions from agricultural sources. ...
Article
Countries in sub-Saharan Africa (SSA) rely on IPCC emission factors (EF) for GHG emission reporting. However, these were derived for industrialized livestock farms and do not represent conditions of smallholder farms (small, low-producing livestock breeds, poor feed quality, feed scarcity). Here, we present the first measurements of CH4 and N2O emissions from cattle-manure heaps representing feeding practices typical for smallholder farms in the highlands of East Africa: 1) cattle fed below maintenance energy requirements to represent feed scarcity, and 2) cattle fed tropical forage grasses (Napier, Rhodes, Brachiaria). Sub-maintenance feeding reduced cumulative manure N2O emissions compared to cattle receiving sufficient feed but did not change EFN2O. Sub-maintenance feeding did not affect cumulative manure CH4 emissions or EFCH4. When cattle were fed tropical forage grasses, cumulative manure N2O emissions did not differ between diets, but manure EFN2O from Brachiaria and Rhodes diets were lower than the IPCC EFN2O for solid storage (1%, 2019 Refinement of IPCC Guidelines). Manure CH4 emissions were lower in the Rhodes grass diet than when feeding Napier or Brachiaria, and manure EFCH4 from all three grasses were lower than the IPCC default (4.4 g CH4 kg⁻¹ VS, 2019 Refinement of IPCC Guidelines). Regression analysis revealed that manure N concentration and C:N were important drivers of N2O emissions, with low N concentrations and high C:N reducing N2O emissions. Our results show that IPCC EFs overestimate excreta GHG emissions, which calls for additional measurements to develop localized EFs for smallholder livestock systems in SSA.
... Barns are also sources of nitrous oxide emissions. In fact, evidence from California for dairy suggests that IPCC nitrous oxide emission factors are generally underestimated (Owen and Silver 2015), although the much cooler temperatures in Denmark may differentiate it. More frequent manure removal would also greatly reduce barn nitrous oxide emissions. ...
Article
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Can the world meet growing demand for food while sharply reducing greenhouse gas emissions from agriculture – and without converting more forests into agriculture? In the World Resources Report: Creating a Sustainable Food Future, WRI set forth a challenging, global five-course menu of actions to do so. How should a country adapt this menu to its own agricultural context? A Pathway to Carbon Neutral Agriculture in Denmark answers this question for Denmark, a country whose major agricultural organizations have committed to become carbon neutral by 2050. A number of lessons are noteworthy, including: The importance of investing in developing, deploying and continuously improving agricultural technologies to mitigate climate change; Nations can’t reduce agricultural greenhouse gas emissions just by producing less food—that would just shift emissions to other countries. Rather, the world will need to produce more food, but on the same (or less) amount of land as today; and Increased food production must be linked with progress on reducing emissions and restoring forests and peatlands. The report’s lessons can inform not only Denmark’s agricultural future, but also that of other advanced agricultural economies.
... Major contribution of N 2 O emissions from solid storage and drylot was mainly due to two reasons: i) large manure collection and management from buffaloes, dairy and non-dairy cattle and ii) higher nitrogen (N) excretion rate which is 40, 60 and 40 kg/head/year for buffaloes, dairy and non-dairy cattle, respectively, while less emission contribution from poultry waste management system was due to lower N excretion rate (0.6 kg/head/year). Similar findings were reported by Owen and Silver (2014) in their study which declared corrals and solid manure piles as major sources of N 2 O emissions contributing about 1.5 + 0.8 and 1.1 + 0.7 kg N 2 O per head per year, respectively. Similarly, Patra (2014) study also confirmed that the major emission contributors were buffaloes (31.4%) followed by 26.8% of cattle, 15.8% of goats, 15% of poultry, 7.8% of sheep and the rest by other livestock types. ...
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Reducing greenhouse gas (GHG) emissions is a global concern after Paris Agreement (PA). Identification of GHG emission sources and accurate and precise estimation of the corresponding emissions is the first step to meet reduction targets under PA. Increasing share of agricultural emissions in the global concentration has raised concerns on this sector. Now, reducing agricultural emissions without compromising food security is a real challenge. The present study was aimed to provide the current emission profile of Pakistan’s agriculture, historical emission trends and future projections under agricultural growth scenarios according to prescribed guidelines of Intergovernmental Panel on Climate Change (IPCC) for national GHGs inventory development. In this study, GHG emissions were estimated using United Nations Framework Convention on Climate Change (UNFCCC) Non-Annex-I Inventory Software (NAIIS), version 1.3.2 as per prescribed Revised 1996 IPCC Guidelines. In these emission estimations, tier-1 approach (which employs default emission factors) was used in accordance with national circumstances and data availability in the country. The emissions baseline was projected for 2030 under business as usual (BAU), food security (FS) and enhanced consumption pattern (ECP) scenarios. Agriculture sector emitted 174.6 million tons (Mt) of carbon dioxide equivalent (CO2-equivalent) emissions, of which 89.8 Mt is methane (CH4) and 83.7 Mt is nitrous oxide (N2O). Carbon monoxide (CO) emissions were found to be 1.07 Mt of CO2-equivalent. Emission from agricultural soils constituted 45.5% of the total agricultural emissions followed by 45.1% from enteric fermentation and 6.5% from livestock manure management. The rest of 1.7% of the emissions were from rice cultivation followed by 1.1% from burning of crop residue. Historical emission trends showed that the agricultural emissions grew from 71.6 to 174.6 Mt of CO2-equivalent from 1994 to 2015, a 143.8% increase over the period of 21 years. Emissions baseline projections were found to be 271.9, 314.3 and 362.9 Mt tons of CO2-equivalent under BAU, FS and ECP scenarios, respectively.
... However, this was not the case for the vermifilter CH 4 emissions. Also, the lagoon CH 4 flux rates measured in this study are comparable with the emissions rate of 20 kg CH 4 m − 2 yr − 1 reported by Owen and Silver (2014) for dairy anaerobic lagoons. They are also within the range of 0.4-37 kg CH 4 m − 2 yr − 1 (12-1030 kg CH 4 ha − 1 day − 1 ) summarized by Leytem et al. (2017) and also reported by Kupper et al. (2020). ...
Article
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Liquid storage of manure is a leading cause of methane emissions from the dairy sector and an important source of air and water pollution. This study monitored the effect of vermifiltration on methane emissions and water quality at a California dairy that uses an anaerobic lagoon. Methane fluxes and wastewater removal rate of volatile solids, N species, salinity, major ions, and trace elements were monitored for 12 months. Vermifiltration reduced methane emissions relative to an anaerobic lagoon by 97–99% and removed 87% of the volatile solids, contaminants such as salts and trace elements, P (83%) and N (84%) from the wastewater. Vermifiltration of dairy wastewater demonstrated to be a useful tool to mitigate methane emissions, regulate excess nutrients and improve water quality at dairy farms.
... Many factors, like the animal diet and its protein content, the type of storage and the farming system, influence the production of N 2 O from manure. In order to determine which variables are the principal players affecting N 2 O emissions on milk producing commercial farms, several studies have been conducted and employed different systems of analysis [6][7][8][9]. Unfortunately, most published studies focus on just a part of the N 2 O emission sources in the dairy farm and rarely consider the entire dairy farm system. The effect of animal diet is often not included in the calculation and just the quantity of the manure is considered. ...
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The N2O emissions of 21 dairy farms in Germany were evaluated to determine the feasibility of an estimation of emissions from farm data and the effects of the farm management, along with possible mitigation strategies. Emissions due to the application of different fertilisers, manure storage and grazing were calculated based on equations from the IPCC (Intergovernmental Panel of Climate Change) and German emission inventory. The dependence of the N2O emissions on fertiliser type and quantity, cultivated crops and diet composition was assessed via correlation analysis and linear regression. The N2O emissions ranged between 0.11 and 0.29 kg CO2eq per kilogram energy-corrected milk, with on average 60% resulting from fertilisation and less than 30% from fertiliser storage and field applications. The total emissions had a high dependence on the diet composition; in particular, on the grass/maize ratio and the protein content of the animal diet, as well as from the manure management. A linear model for the prediction of the N2O emissions based on the diet composition and the fertilisation reached a predictive power of R2 = 0.89. As a possible mitigation strategy, the substitution of slurry for solid manure would reduce N2O emissions by 40%. Feeding cows maize-based diets instead of grass-based diets could reduce them by 14%.
... The NZ GHG Inventory calculations now assume that 8.5% of manure from lactating cows is deposited in the yard and stored in effluent ponds, which is an increase from 6% prior to 2015 (MPI 2019). Storage of dairy effluent in large ponds is not unique to NZ, but is widespread around the globe wherever dairy farming is a major farming activity (Owen and Silver 2015). ...
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PurposeThe New Zealand Government requires gross emissions of biogenic methane (CH4) to be reduced to 10% below 2017 levels by 2030. However, the amount of CH4 emissions reported in the ‘Manure Management’ category of New Zealand’s Greenhouse Gas Inventory has increased by 123% since 1990. The purpose of this research was to determine the effect of treating farm dairy effluent (FDE) with polyferric sulphate (PFS) on CH4 emissions.Methods The effect of treating FDE with PFS on CH4 emissions was measured at four scales: (i) 1-L gas jars in the laboratory, (ii) 1.1-m-deep × 150-mm-diameter pipe microcosms in the laboratory, (iii) large 3.4-m-deep × 0.47-m-diameter pipes on-farm, and (iv) 2-m-deep × 8.4-m-diameter (100,000 L) commercial effluent storage tanks on a farm. Gas emissions were captured by repeated discrete sampling and CH4 concentrations were determined by gas chromatography.ResultsWe discovered that treating FDE with PFS at an average rate of 220 mg Fe L−1 of FDE reduced CH4 emissions by up to 99% and that this effect continued for an extended period of time (up to 2 months) after treatment. The PFS treatment also reduced CO2 emissions by approximately 50% and reduced hydrogen sulphide emissions. PFS treatment resulted in a small increase in nitrous oxide (N2O) emissions, but these emissions were very low and only represented < 3% of the total CO2-e greenhouse gas emissions from the treated FDE.ConclusionsA new method to reduce CH4 emissions from farm dairy effluent by up to 99% has been discovered.
... Organic manures account for almost 10% of GHG emissions from agriculture globally (Owen and Silver 2015) and 1% of the total emission in India (Pathak 2015). Vermicompost contained higher N content compared to conventional farmyard manure and compost (Chatterjee et al. 2016b) and requirement of vermicompost is almost half of the dose of farmyard manure. ...
Chapter
Reduction in the emission of methane is a challenge to the global scientific community. The global warming potential of methane is about 28–36 making it capable of trapping heat in the atmosphere and contribute to global warming. In this chapter we have described the mechanism and various pathways of methane formation, and discussed the mechanism of methane transport to atmosphere by diffusion, aerenchyma transport, and ebullition. Apart from this, we have also narrated various microbial and non-microbial sources of methane and various factors that control methane emission. Aerobic methane oxidation is a process by which methane produced under anaerobic environment are oxidized to carbon dioxide by methanotrophs, which has been explained in this chapter. Besides, we have discussed various methodologies of water, fertilizer, manure management for controlling methane emission.
... Composting can transform agricultural and municipal waste into a valuable soil amendment which increases SOC [7,8], while at the same time increasing soil nutrients and yields [9,10]. Both dairy manure [11] and food waste [12,13] have negative environmental effects, and composting offers one solution to recycle these wastes. For example, dairy manure compost applied at a rate of 105 Mg DM ha -1 increased SOC by 73% and supported corn yields similar to that of inorganic fertilizer [14]. ...
Article
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Composting is an effective strategy to process agricultural and urban waste into forms that may be beneficial to crops. The objectives of this orchard field study were to characterize how a dairy manure compost and a food waste compost influenced: (1) soil nitrogen and carbon pools, (2) bacterial and nematode soil food webs and (3) tree growth and leaf N. The effects of composts were compared with fertilized and unfertilized control plots over two years in a newly planted almond orchard. Both dairy manure compost and food waste compost increased soil organic matter pools, as well as soil nitrate and ammonium at certain time points. Both composts also distinctly altered bacterial communities after application, specifically those groups with carbon degrading potential, and increased populations of bacterial feeding nematodes, although in different timeframes. Unique correlations were observed between nematode and bacterial groups within compost treatments that were not present in controls. Food waste compost increased trunk diameters compared to controls and had greater relative abundance of herbivorous root tip feeding nematodes. Results suggest that recycled waste composts contribute to biologically based nitrogen cycling and can increase tree growth, mainly within the first year after application.
... Approximately 10% of the global GHG emissions from agriculture are produced from livestock manure management, contributing an equal proportion to the US methane emission inventory [9]. In California, anaerobic lagoons are the most common strategy for manure management, and these lagoons are considered the largest source of CH 4 emissions after enteric fermentation. ...
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Animal manure is a source of greenhouse gas (GHG) emissions and other pollutants and nuisances such as ammonia and odors. There are several technologies to reduce emissions on animal farms including manure additives; however, few have been proven effective and easy to apply to dairy lagoon systems. The present research aimed at testing the ability of the commercial additive “SOP LAGOON” to reduce emissions of GHGs (i.e., carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)), as well as ammonia (NH3) and odors from lagoon stored liquid manure. Emissions of GHGs, NH3 and odors were measured in the laboratory from barrels filled with 65 L of manure treated with SOP LAGOON or left untreated as a control. Manure was collected from a commercial dairy that is located in Solano County, California. Emissions of GHGs and NH3 were continuously measured for one week using flux chambers placed on top of the barrels and connected to a mobile air emissions laboratory. The effects of the untreated control, versus the two respective treatment additive doses of 30.8 and 61.6 g/m3 of manure were compared to each other. The low dose was selected based on the manufacturer recommendation and the high dose was selected by doubling the low dose. Results showed that SOP LAGOON applied at the high dose (61.6 g of SOP LAGOON per m3 of manure) versus the control greatly reduced (p < 0.05) emissions of CO2, CH4, N2O and NH3 by 14.7%, 22.7%, 45.4% and 45.9%, respectively. Furthermore, the high dose of SOP LAGOON treated samples versus the control samples showed less odor intensity (p < 0.05). There was no significant effect of the low dose of SOP LAGOON on the emissions of different gases. The HIGH dose of SOP LAGOON might decrease the number of methanogens and hydrolytic microorganisms and their excreted enzymes during manure storage. Further studies are needed to investigate the mechanism of emission reduction using SOP LAGOON.
... was used with a specific keyword series for each type of animal production and emission source. To ensure a thorough review, the list of publications was later compared with those of some major international reviews on gas emissions from livestock systems (Giner-Santonja et al., 2017;Griffing et al., 2007;Hafner et al., 2018;Hassouna et al., 2015a;Hristov et al., 2011;Jayasundara et al., 2016;Meda et al., 2011;Niu et al., 2018;Owen and Silver, 2015;Peyraud et al., 2012;Philippe et al., 2011;Philippe and Nicks, 2015;Sintermann et al., 2012;Webb et al., 2010), which covered different periods from 1981 to 2017. ...
Article
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Growing demand for animal products has contributed to an increase in biogeochemical fluxes, leading particularly to gaseous ammonia, methane, and nitrous oxide emissions into the atmosphere. Developing accurate knowledge on the sources and magnitude of gas emissions from the livestock sector is essential to reducing emissions, while meeting other societal expectations, and to implementing effective regulations. To this end, a database called ELFE (ELevage et Facteurs d’Emission; i.e., Livestock and Emission Factors) was recently developed. It currently contains ?5200 gas emission measurements extracted from 345 publications of the international literature published from 1964 to 2018 from 37 countries. One of its innovative aspects is the structured and comprehensive description of both the livestock system and the measurement method associated with emission data. Ammonia emitted by livestock systems represents 40 to 80% of emission values and 45 to 81% of the values concern production systems with slurry, depending on the animal produced. This database will contribute to improved emission factors for national inventories by more thoroughly considering factors influencing emission levels and data quality. It highlights the need for shared and standardized reporting protocols for both the livestock system itself and the measurement conditions, to allow for thorough comparisons and to reduce uncertainty in unit conversions. The database is available online on the Institut national de la recherche agronomique (INRA) platform (https://data.inra.fr/dataset.xhtml?persistentId=doi:10.15454/MHJPYT) and will be updated annually with new gas emissions.
... In such anaerobic decomposition, when the manure is stored or treated as a liquid in tanks or pits, the process significantly influences the methane emissions. The manure management through biogas plants can help in methane recovery which can be used for energy generation [18,31] . The degree of methanogenesis is also depended on the temperature and the duration of retention in storage tank/container [25] . ...
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Globally livestock has been recognized as one of the major contributors of methane emissions. Enteric fermentation by ruminant livestock viz., cattle, buffalo, sheep and goats has been the major source of methane emission. Although livestock sector is envisaged to grow further to meet increasing demand of food from animal produce, necessity of methane mitigation strategies through different management measures are also emphasised in order to reduce the climate change impacts. In the present paper possible methane mitigation measures from livestock production systems through different management strategies viz., dietary manipulation, proper selection of animal breeds, manure management and other advanced technologies have been discussed.
Article
Husbandry trace gases that have climate change implications such as carbon dioxide (CO2), methane (CH4) and ammonia (NH3) can be quantified through remote sensing; however, many husbandry gases with health implications such as hydrogen sulfide (H2S), cannot. This pilot study demonstrates an approach to derive H2S concentrations by coupling in situ and remote sensing data. Using AMOG (AutoMObile trace Gas) Surveyor, a mobile air quality and meteorology laboratory, we measured in situ concentrations of CH4, CO2, NH3, H2S, and wind at a southern California university research dairy. Emissions were 0.13, 1.93, 0.022 and 0.0064 Gg yr⁻¹; emission factors (EF) were 422, 6333, 74, and 21 kg cow⁻¹ yr⁻¹, respectively, for the 306 head herd. Contributing to these strong EF were spillway emissions from a grate between the main cowshed and the waste lagoon identified in airborne remote sensing data acquired by the hyperspectral thermal infrared imager, Mako. NH3 emissions from the Chino Dairy Complex, also in southern California, were calculated from Infrared Atmospheric Sounding Interferometer (IASI) satellite data for 2008–2017 using average morning winds, yielding a flushing time of 2.7 h, and 8.9 Gg yr⁻¹. The ratio of EF(H2S) to EF(NH3) for the research dairy from AMOG data were applied to IASI NH3 emissions to derive H2S exposure concentration maps for the Chino area, which ranged to 10–30 ppb H2S for many populated areas. Combining remote sensing with in situ concentrations of multiple emitted gases can allow derivation of emissions at the sub-facility, facility, and larger scales, providing spatial and temporal coverage that can translate into exposure estimates for use in epidemiology studies and regulation development. Furthermore, with high fidelity information at the sub-facility level we can identify best practices and opportunities to sustainably and holistically reduce husbandry emissions.
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There has been an increasing interest in continuous base-load low-carbon renewable energy generation in the United States. Several technologies have been developed to convert biomass into energy, and anaerobic digestion is one such technology to convert food waste and animal manure into power by biochemical conversion and combustion. Many studies have looked at the optimization of the biomass supply chains in combination with environmental impacts. However, there are very few studies in the literature for determining the optimum location of biopower plants fed by food waste and manure. This study evaluates the optimum locations, sizes, and the number of plants for biopower production in Wisconsin using both mixed-integer linear programing and geographic information system network analysis (ArcGIS V10). The main objective of the study is to maximize the profits of biopower facilities accounting for both the profits from the biopower supply chain and carbon credits. In this study, two scenarios (base case and a future case) were evaluated by varying the carbon credits and the food waste tipping fee: the base case with $0 carbon credits and $0 food waste tipping fee and the future case with $15/ton CO2 savings and $40 tipping fee/ton collected for the food waste. The key results showed that the inclusion of a carbon credit and tipping fee policies increased the profitability of biopower production and predicted an increase in biopower production capacity from 15 to over 77 MW in WI, representing 1% of its annual electricity consumption.
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Supercontinuum (SC) lasers provide an excellent opportunity for absorption spectroscopy by virtue of their high brightness and large bandwidth. Here we present the detection of multiple industrial toxic gasses from 1480 nm to 1700 nm, with a simple custom SC laser source. Using readily available optical components, we demonstrate an all-fiber system for the detection of ammonia (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) and methane (CH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) in a 2.4 m long hollow-core photonic bandgap fiber with 20-μm core diameter. The responsivity, selectivity, and performance of the system for continuous detection are demonstrated.
Article
Owing to the economic benefit and efficiency, H2SO4-acidification is often applied for reducing CH4 emissions during storage of pig slurry (PS). However, it encounters with several problems related with safety and the concomitant H2S emissions. To reduce the required amount of H2SO4, in this study, the storage at low temperature (20-35 °C) was applied to the mild-acidified PS (pH 6.5 and 7.0). 55.1 kg CO2 eq./ton PS of CH4 was emitted from the control (non-acidified at 35 °C), which was reduced to 14.4-40.2 kg CO2 eq./ton PS at 20-30 °C. Temperature-decrease led to the increase of the abundance of methanogens (Methanobrevibacter and Methanolobus) that can grow at low temperature and the drop of specific methanogenic activity value. To achieve 70% CH4 reduction, 1.6 kg H2SO4/ton PS was needed in PS acidification, which was decreased to 0.5 kg H2SO4/ton PS by decreasing temperature from 35 °C to 25 °C. CH4 production potential of the PS stored at 35 °C-pH 6.5 and 25 °C-pH 7.0 was increased by 21-33% compared to the control. The GHG reduction of 33.6-41.9 kg CO2 eq./ton PS and the profit of 6.6 USD/ton PS could be attained by applying acidification or combined storage, indicating that the temperature-decrease can be effectively combined with H2SO4-acidification.
Article
On-farm greenhouse gas (GHG) emissions from cows, manure, and fields (to produce feed) comprise more than 72 % of the United States milk carbon footprint. Recent studies examined the impact of dietary strategies on enteric methane emissions, however, tradeoffs between enteric methane and manure related GHG emissions have not been determined. Thus, the objective of this study was to determine the carry-over effects of dairy cow breed and diet on manure composition and manure GHG emissions during storage and after field application. The GHG emissions were measured using static chamber method for 50 days (d) during storage and 50-d after field application (30-d in the fall and 20-d in the following spring) of manure collected from four Holstein and four Jersey cows fed either alfalfa silage or corn silage based diets containing low forage neutral detergent fiber (FNDF) or high FNDF. None of the interactions among treatment factors were significant (P > 0.10). Manure composition was affected by both FNDF level and FNDF source but not cow breed. For example, manure pH was lower for low FNDF-fed than high FNDF-fed cows and concentrations of organic matter, total carbon, and neutral detergent fiber were greater in manure of corn silage-fed than alfalfa silage-fed cows. Except for starch (which was in low concentration), all the measured manure characteristics changed during the storage period. Treatments did not affect either hourly CO2, methane and nitrous oxide emissions, nor cumulative emissions (over 50-d of storage or over 50-d after land application), except for a tendency (P < 0.10) to emit 22% lower manure CO2 by high FNDF-fed cows than low FNDF-fed cows. Cumulative methane and nitrous oxide emissions were respectively 25 times greater and 19 times lower during the 50-d manure storage period than the subsequent 50-d after field application. Cumulative field nitrous oxide emission was 17 times greater during spring than fall. Depending on mode of expression (emissions per kg manure or per kg milk or per cow basis), manure of low FNDF-fed cows tended to emit 51 to 72% greater 100-d (combined storage and field) non-CO2 GHG emissions than high FNDF-fed cows. However, in this study, neither cow breed nor FNDF source affected the 100-d combined non-CO2 GHG emissions.
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Greenhouse gas emissions from meat and dairy production are often highly uncertain; these emissions are typically estimated using inventory-based, ‘bottom-up’ models, which contain uncertainties that are difficult to quantify. Modeled emissions estimates can be corroborated using atmospheric measurements—taken above and downwind of animal production regions—to produce ‘top-down’ emissions estimates. Top-down and bottom-up estimates of animal methane show good agreement when considering global emissions. However, in the US, where animal production is predominantly highly intensified with confined feeding operations, animal methane emissions may be 39%–90% higher than bottom-up models predict (expressed as mean differences across studies). Animal emissions may grow in the future as meat and dairy demand increases in developing countries. We examine East and Southeast Asia as a test case, where emissions from increased meat and dairy production are expected to be offset by improved efficiency from intensive methods. We adjust the share of direct emissions projected to come from intensive systems by the intensities derived from US top-down estimates. We find that region-wide emissions from meat and milk production could reach 1.52 (1.41–1.62) GtCO2eq by 2050, an amount 21% (13%–29%) higher than previously predicted. Therefore, intensification may not be as effective in mitigating emissions in developing countries as is commonly assumed.
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Evolutionary, meat consumption has meant a great step for humankind, even today, despite the different culinary options, meat is still a fundamental protein source for humans. Nonetheheless, and especially after Industrial Revolution, meat production has become an important source of environmental deterioration, fundamentally due to the handling practice developed since then. In this work, the impacts that animal husbandry has on the environment, the tools developed to measure the impacts, and the mitigation strategies that have been proposed by the scientific community have been reviewed. To reach sustainable meat production three objectives must be proposed: 1) Reduction in the use and contamination of water; 2) Avoid soil degradation, and 3) Reduce greenhouse gas emission. These goals can be reached through the change of handling practices. In some countries, these strategies have been already carried out tending to emissions reduction from 26% until 112%. Authors like Allan Savory and Frank Mitloehner suggest that husbandry can be a mitigating situation facing environmental change.
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In Denmark, agriculture is the largest source of anthropogenic methane emissions (81%), mainly from cattle (dairy and beef) farms. Whole-farm methane emissions were quantified at nine Danish cattle farms, using the tracer gas dispersion method. Five to six measurement campaigns were carried out at each farm, covering a full year. Of the nine cattle farms, seven were home to dairy cows and two to beef cattle. The farms represented typical breeds, housing and management systems used in Denmark. Whole-farm methane emission rates ranged from 0.7 to 28 kg h⁻¹, with the highest measurements seen at locations with the highest number of animals. Emissions tended to be higher from August to October, due to elevated temperatures and high amounts of stored manure during this period of the year. The average emission factor (EF) for dairy cow farms was 26 ± 8.5 g Livestock Unit (LU)⁻¹ h⁻¹, whereas it was 16 ± 4.1 LU⁻¹ h⁻¹ for beef cattle farms, i.e. 38% lower for the latter. The use of deep litter house management explained some of the differences found in the EFs for dairy cows. Methane emission rates estimated using IPCC models and national guidelines tended, on average for all farms and measurements, to be underestimated by 35% in comparison with the measured methane emissions, for all models and farms. The results suggest that future improvements to inventory models should focus on enteric methane emissions from beef cattle and manure methane emissions for both dairy cows and beef cattle, especially from deep litter management.
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Robust air pollutant emission reduction strategies rely on accurate source characterizations. Studies have reported that the methane (CH4) emissions from California’s dairy sector are highly variable, and raised questions regarding the representativeness of the statewide CH4 emission estimates. To address these questions, a multi-tiered field study was conducted to evaluate the dairy CH4 emission factors (EFs) used in the California Air Resources Board (CARB) emission inventory. These EFs for dairy cow enteric fermentation and anaerobic lagoons are 144 and 332 kg of CH4 per animal head per year. CH4 emissions from dairies located within the San Joaquin Valley (SJV) were characterized through the analysis of ground-level mobile measurements collected in the summer and the fall of 2019. We developed a novel dispersion modeling-based approach that uses the ground-level mobile measurements of ambient CH4 levels to generate a metric that evaluates the CARB CH4 EFs. The analysis was further expanded using airborne measurements collected between September 2017 and May 2020. The multi-tiered measurements resulted in 126 whole-farm CH4 emission estimates for 107 dairies, making this study the most comprehensive mobile research study focused on CH4 emissions from California dairies to date. CARB CH4 EFs represented dairy CH4 emissions captured in this study fairly well; emissions observed in ground-level mobile measurements in summer and fall, and airborne measurements were greater than the inventory-reported values by only 8% (95% Confidence Interval [CI95%]: -7%–31%), 3% (CI95%: -11 – 21%), and 10% (CI95%: -7 – 45%), respectively. The results underline the effects of meteorology on dairy emissions and suggest that CH4 EFs from dairies with different ranges of herd sizes did not vary significantly. Future evaluation of the CARB CH4 emission inventory must incorporate facility-level data and leverage mechanistic approaches that capture the temporal variation of emissions from California’s dairy farms. Such improvements would enable research studies to better inform the emission inventory and help track the emissions changes from the implementation of new manure management technologies across California.
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Composted manure and green waste amendments have been shown to increase net carbon (C) sequestration in rangeland soils and have been proposed as a means to help lower atmospheric CO2 concentrations. However, the effect of climate change on soil organic C (SOC) stocks and greenhouse gas emissions in rangelands is not well understood, and the viability of climate change mitigation strategies under future conditions is even less certain. We used a process‐based biogeochemical model (DayCent) at a daily timestep to explore the long‐term effects of potential future climate changes on C and greenhouse gas dynamics in annual grassland ecosystems. We then used the model to explore how the same ecosystems might respond to climate change following compost amendments to soils and determined the long‐term viability of net SOC sequestration under changing climates. We simulated net primary productivity (NPP), SOC, and greenhouse gas fluxes across seven California annual grasslands with and without compost amendments. We drove the DayCent simulations with field data and with site‐specific daily climate data from two Earth system models (CanESM2 and HadGEM‐ES) and two representative concentration pathways (RCP4.5 and RCP8.5) through 2100. Net primary productivity and SOC stocks in unamended and amended ecosystems were surprisingly insensitive to projected climate changes. A one‐time amendment of compost to rangeland acted as a slow‐release organic fertilizer and increased NPP by up to 390–814 kg C ha‐1 y‐1 across sites. The amendment effect on NPP was not sensitive to Earth system model or emissions scenario and endured through the end of the century. Net SOC sequestration amounted to 1.96 ± 0.02 Mg C ha‐1 relative to unamended soils at the maximum amendment effect. Averaged across sites and scenarios, SOC sequestration peaked 22 ± 1 years after amendment and declined but remained positive throughout the century. While compost stimulated nitrous oxide (N2O) emissions, the cumulative net emissions (in CO2 equivalents) due to compost were far less than the amount of SOC sequestered. Compost amendments resulted in a net climate benefit of 69.6 ± 0.5 Tg CO2e 20 ± 1 years after amendment if applied to similar ecosystems across the state, amounting to 39% of California’s rangeland. These results suggest that the biogeochemical benefits of a single amendment of compost to rangelands in California are insensitive to climate change and could contribute to decadal‐scale climate change mitigation goals alongside emissions reductions.
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While studies have shown that anaerobic co-digestion of chicken manure (CM) and corn stover (CS) is an efficient method to treat these agricultural wastes, the microbial ecology of these systems and optimal parameters for the digestion process are yet to be determined. In this study, the effects of different initial substrate concentrations and CS : CM mixture ratios on co-digestion and microbial community structure were evaluated. Results demonstrated that both the highest cumulative methane yields and methane production rates were obtained from reactors with a CS : CM ratio of 1 : 1 during hemi-solid-state anaerobic digestion (HSS-AD). Cumulative methane yields and methane production rates were 24.8% and 42% lower in solid-state anaerobic digestion (SS-AD) reactors using the same CS : CM ratios. Analysis of microbial community structures revealed that cellulolytic bacteria and a diversity of syntrophic microorganisms capable of direct interspecies electron transfer (DIET) and hydrogen interspecies transfer (HIT) were enriched in the best-performing reactors. Methanosarcina species also dominated during HSS-AD, and their presence was positively correlated with methane production in the reactors.
Conference Paper
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The reduction of greenhouse gas emissions is becoming more important world-wide. Although research suggests that farmland can serve as a sink for carbon, agriculture is also an important source of emissions. As a sector, agriculture is reported to be the greatest contributor of nitrous oxide and the third greatest contributor of methane in the U.S. Thus, strategies must be designed to reduce or eliminate net emissions of greenhouse gases. Before these strategies can be developed, we must first understand typical emission ranges from each source at the farm level in order to focus on the processes with the greatest emissions. Sources on dairy farms include soil, growing crops, feed storage, animals, and manure in animal housing facilities, during storage, and following field application. Other countries, particularly in Europe, have quantified emission ranges, although these data are less established within the U.S. An extensive literature review was conducted to determine the major processes contributing to greenhouse gas emissions from dairy farms and to quantify typical emission levels. From these typical levels, emissions were estimated for a representative dairy farm. This review and farm analysis will help direct modeling efforts by determining the important physical processes that drive emissions of carbon dioxide, methane, and nitrous oxide in dairy production. The review also expands the knowledge base of researchers, farm planners, and policymakers as they work to develop and maintain sustainable farming systems.
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Methane (CH 4) is the most abundant non-CO 2 greenhouse gas and because it has a much shorter atmospheric lifetime (~9years) than CO 2 it holds the potential for more rapid reductions in radiative forcing than would be possible by controlling emissions of CO 2 alone. There are several important anthropogenic sources of CH 4 : ruminants, the fossil fuel industry, landfills, biomass burning and rice production (Fig.1c). We focus on ruminants for four reasons. First, ruminant production is the largest source of anthropogenic CH 4 emissions (Fig.1c) and globally occupies more area than any other land use. Second, the relative neglect of this greenhouse gas source suggests that awareness of its importance is inappropriately low. Third, reductions in ruminant numbers and ruminant meat production would simultaneously benefit global food security, human health and environmental conservation. Finally, with political will, decreases in worldwide ruminant populations could potentially be accomplished quickly and relatively inexpensively. Ruminant animals consist of both native and domesticated herbivores that consume plants and digest them through the process of enteric fermentation in a multichambered stomach. Methane is produced as a by-product of microbial digestive processes in the rumen. Non-ruminants or 'monogastric' animals such as pigs and poultry have a single-chambered stomach to digest food, and their methane emissions are negligible in comparison. There are no available estimates of the number of wild ruminants, but it is likely that domestic ruminants greatly outnumber the wild population, with a reported 3.6billion domestic ruminants on Earth in 2011 (1.4 billon cattle, 1.1 billion sheep, 0.9 billion goats and 0.2 billon buffalo) 2 . On average, 25million domestic ruminants have been added to the planet each year (2million per month) 2 over the past 50years (Fig.1d). Worldwide, the livestock sector is responsible for approximately 14.5% of all anthropogenic greenhouse gas emissions 3 (7.1of 49GtCO 2 eyr –1). Approximately 44% (3.1GtCO 2 eyr –1) of the livestock sector's emissions are in the form of CH 4 from enteric fermentation, manure and rice feed, with the remaining portions almost equally shared between CO 2 (27%, 2GtCO 2 eyr –1) from land-use change and fossil fuel use, and nitrous oxide (N 2 O) (29%, 2GtCO 2 eyr –1) from fertilizer applied to feed-crop fields and manure 3 . Ruminants contribute significantly more (5.7GtCO 2 eyr –1) to greenhouse gas emissions than monogastric livestock (1.4GtCO 2 eyr –1), and emissions due to cattle (4.6GtCO 2 eyr –1) are substantially higher than those from buffalo (0.6GtCO 2 eyr –1) or sheep and goats (0.5GtCO 2 eyr –1) 3 . Globally, ruminants contribute 11.6% and cattle 9.4% of all greenhouse gas emissions from anthropogenic sources. The total area dedicated to grazing encompasses 26% of the terrestrial surface of the planet 4 . Livestock production accounts for 70% of global agricultural land and the area dedicated to feed-crop production represents 33% of total arable land 4 . The feeding of crops to livestock is in direct competition with producing crops for human consumption (food security) and climate mitigation (bioenergy production or carbon sequestration) 5 . Deforestation has been responsible for a significant proportion of global greenhouse gas emissions from the livestock sector and takes place mostly in tropical areas, where expansion of pasture and arable land for animal feed crops occurs primarily at the expense of native forests 4,6 . Lower demand for ruminant meat would therefore reduce a significant driver of tropical deforestation and associated burning and black carbon emissions. The accompanying reduction in grazing intensity could also allow regrowth of forests and other natural vegetation, resulting in additional carbon sequestration in both biomass and soils with beneficial climate feedbacks 5,6 . Lower global ruminant numbers would have simultaneous benefits for other systems and processes. For example, in some grassland and savannah ecosystems, domestic ruminant grazing contributes to land degradation through desertification and reduced soil organic carbon 5 . Ruminant agriculture can also have negative impacts on water quality and availability, hydrology and riparian ecosystems 4,7 . Ruminant production can erode biodiversity through a wide range of processes such as forest loss and degradation, land-use intensification, exotic plant invasions, soil erosion, persecution of large predators and competition with wildlife for resources 4–7 . Ruminant production also has implications for food security and human
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Methane (CH4) emissions from stored slurry were successfully measured by a micrometeorological mass balance technique. Emissions during autumn to late winter ranged from 2 to 100kgCH4-Cha–1day–1. Diurnal variations of CH4 emissions were investigated by measuring emissions at several times during the day, correlated with slurry temperatures at 10cm depth and successfully modelled with the Arrhenius equation.
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Feedlot manure is a source of atmospheric ammonia (NH3), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), gases that are considered a risk to the environment. However, accurate estimates of emission of these gases from stockpiled manure are sparse due the lack of suitable measuring techniques. In our study, the integrated horizontal flux (IHF) and the backwards Lagrangian stochastical (bLS) dispersion micrometeorological techniques were adapted to measure gas emissions (NH3, CH4, N2O and CO2) from a manure pile. The results were compared with measurements using the static chamber technique. Net horizontal gas fluxes were determined by mounting passive NH3 samplers, gas intakes for CO2 and CH4, and anemometers on poles that were always located up- and downwind of the pile as controlled by a wind vane. Further, NH3 emission was estimated with the bLS technique using NH3 concentration measured with a laser downwind of the pile. NH3 emission measured with the IHF and bLS techniques were similar. Periodic measurements of emissions of CO2 with the IHF technique by taking air samples with syringes and measuring CO2 and CH4 concentrations on a gas chromatograph, were similar to continuous measurements with the IHF technique measuring gas concentrations with an infrared gas monitor. Emissions of CO2, CH4 and N2O measured with the static vented chamber technique were 12–22% of that measured with the IHF technique. Our results show that measurements of gas emission from stockpiled manure depend on the measuring technique and emphasizes the need for further validation of these techniques.
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Conference Paper
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Chapter
As the name implies, the gases that assist in capturing heat in the atmosphere are termed as greenhouse gases (GHGs). The continuously rising concentrations of these gasses are believed to work against nature’s natural process, trapping more heat than what is needed leading to an increase of earth’s climate temperature. Livestock production operations contribute both directly and indirectly to climate change through the emissions of greenhouse gases such as carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Generally, swine and ruminant livestock operations, especially dairy cows and beef cattle, contribute to the production of GHGs mainly CH4, N2O, and CO2 in the environment. The CH4, CO2, and N2O are considered as direct greenhouse gases. The indirect GHGs include carbon monoxide (CO), oxides of nitrogen (NOx), and non-methane volatile organic compound (NMVOCs). Characterization and quantification of N2O and CH4 emitted from livestock operations are important because these gases are believed to play a major role in the increase of Earth's temperature. During the last two hundred and fifty years, anthropogenic activities, including demanding agricultural production, have increased the global atmospheric concentration of GHG, namely CO2, CH4, and N2O by 36, 148, and 18%, respectively [1]. Total greenhouse gas (GHG) emissions in the US increased by 14.7% from 1990 to 2006. All agricultural sources combined were estimated to have generated 454 Tg (1012g) of CO2 equivalents in the U.S. during 2006 [2]. The CH4 emissions from enteric fermentation and manure management represent about 25 and 8% of the total CH4 emissions from anthropogenic activities. The US Environmental Protection Agency (USEPA), Inventory of U.S. Greenhouse Gas Emissions, and Sinks identified manure management as generating 24 and 5% of CH4 and N2O emissions, respectively, from agricultural sources [2-3]. The USEPA has begun to consider regulating GHGs emitted by the stationary sources, including manure management from CLOs. Thus, it is essential to obtain accurate estimates of GHG emissions from various ground level area sources (barns/housings, lagoons, pens, settling basins, silage piles, pasturelands, etc.) within CLOs to improve emissions inventories and to devise source-specific abatement strategies. In this chapter, GHG emission sources, emissions process, measurement methods and gas sampling protocol, and migration strategies including air scrubbing technology, biofilters, and best manure management practices in the context of livestock waste management were reviewed and discussed.
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This journal published an article by Bellarbyet al. entitled "Livestock greenhouse gas emissions and mitigation potential in Europe" (Bellarbyet al., 2013), which became the sole source for a news release by the European Commission's Joint Research Centre entitled "GHG emissions from the EU livestock sector could be mitigated by up to 60%" (EC, 2013).I will outline four sets of issues that may change the Joint Research Centre's conclusions. The first set of issues relates to Bellarbyet al.'s assertion that "there is only one whole life cycle estimate of GHG emissions from the global livestock sector… which suggested that global contributions from livestock were 18% of total GHG emissions". This article is protected by copyright. All rights reserved.
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The greenhouse gas emissions from agricultural systems contribute significantly to the national budgets for most countries in Europe. Measurement techniques that can identify and quantify emissions are essential in order to improve the selection process of emission reduction options and to enable quantification of the effect of such options. Fast box emission measurements and mobile plume measurements were used to evaluate greenhouse gas emissions from farm sites. The box measurement technique was used to evaluate emissions from farmyard manure and several other potential source areas within the farm. Significant (up to 250 g CH4 m−2 day−1and 0.4 g N2O m−2 day−1) emissions from ditches close to stables on the farm site were found.
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Estimates of methane (CH4) emissions from slurry tanks or lagoons in the past have been made primarily by using chamber techniques, which are point specific and interfere with conditions at the slurry-atmosphere interface. This study is based on the use of sulphur hexafluoride (SF6) as a tracer gas to estimate CH4 transport from the slurry surface. The tracer was released from the surface of the swine slurry, and air samples were taken at the downwind rim of the tank over a 165 day period from June 12 to November 20, 1995, at the McGill University-Macdonald Campus Farm, Ste-Anne-de-Bellevue, Quebec, and analyzed for CH4 and SF6 concentrations (C). Knowing the SF6 source strength (Q), CH4 source strength was then determined from the measured downwind concentrations using the C/Q ratio. Using this method, annual CH4 emission from the swine slurry tank was estimated at 56.5 kg CH4m-2 tank surface yr-1 (+/-20%). Assuming that diffusion processes at the nearby dairy tank were similar to those at the swine tank, the same C/Q ratio was used to determine CH4 emissions from the dairy slurry based on downwind CH4 concentrations measured over the same period as at the swine tank. Annual methane emission from the dairy tank was estimated at 74 kg CH4m-2 tank surface yr-1 (+/-45%). On the basis of these estimates, CH4 emissions from outdoor holding tanks for swine and dairy slurry in Canada were approximated at 0.71 Tg CH4yr-1 (+/-40%) and 0.24TgCH4yr-1 (+/-70%) respectively, giving a combined annual emission of approximately 0.95 Tgyr-1 (+/-50%).
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Intensification of livestock production in many parts of the world has led to increasing atmospheric losses of N in connection with storage and field application of manure. Both types of emissions are influenced by manure organic matter content via mechanisms such as composting, crust formation, mineralization–immobilization turnover, and water retention. Manure management affects the potential for, and balance between, NH3 and N2O emissions. The interaction between NH3 and N2O may be positive (e.g., both emissions are reduced by an airtight cover during storage and stimulated by composting), or negative (e.g., direct N2O emissions from soil will potentially increase if losses of NH3 are prevented during storage or field application). Emissions of NH3 and N2O negatively affect N use efficiency and the greenhouse gas (GHG) balance of livestock production. Ammonia and N2O emissions and GHG balances of manure management, and the mitigation potential of individual and combined measures to prevent emissions, are calculated for dairy cattle with an emission factor approach. A more precise determination of overall N2O and NH3 emissions requires a model that accounts for the complex interactions between C and N transformations at each stage of the manure management chain in a time scale that is relevant for management practices such as retention time in housing and storage, treatment to optimize nutrient management, and timing of field application. Modelling emissions of N2O from field applied manure is a particular challenge due to the heterogeneity in distribution of O2 supply and O2 demand which is introduced.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.
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We describe the potential contribution of on-farm biogas production to reducing greenhouse gas (GHG) emissions and other environmental impacts related to livestock operations. GHG are reduced by production of renewable energy as a substitute for fossil fuels via reduction of fugitive GHG emissions from stored and land applied manures, as well as by reduction in use of chemical fertilizers in crop production. Anaerobic digestion (AD) biotechnologies produce biogas at average rates of 0.30, 0.25 and 0.48L/g volatile solids from swine, bovine and poultry slurries, respectively. The biogas produced is of high quality with a CH4 concentration of 60–80%. AD may be an acceptable solution to management of P surplus by precipitating up to 25% of it in batch or semi-batch operated bioreactors, and by precipitating and concentrating up to 70% of bioreactor effluent P in long term storage bottom sludge. Effluents from AD are better balanced to meet crop needs than raw manure slurries, thereby reducing the need for supplementary chemical N and P fertilizers. Both capture of energy and reduced needs for chemical fertilizers will substantially decrease the C footprint of livestock food products. On-farm biogas production contributes to more sustainable livestock operations by substantially reducing other environmental impacts related to manure management. It reduces the risk of water pollution associated with animal manure slurries (i.e., eutrophication) by removing 0.80–0.90 of soluble chemical oxygen demand. In addition, some AD eliminate zoonotic pathogens and parasites in livestock manures. AD also improves human/farm cohabitation in rural regions by reducing odour emissions by 70–95%. This reduction allows more frequent and better timing of manure land application. Both timing of application and improved nutrient balance have the potential to increase nutrient uptake by crops and minimize nutrient losses to the environment. Reduction in the viability of weed seeds during AD reduces the need for herbicides and makes bioreactor effluent more acceptable to organic farmers. Inadequate regulatory polices and incentives are obstacles to widespread implementation of AD in developed and developing countries. However, adoption of AD is an alternative which could substantially reduce the C and environmental footprint of housed livestock operations.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.
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Climate change has been linked to increasing concentrations of greenhouse gases including CH4, which has a global warming potential 25 times greater than CO2. Stored liquid animal manure is an important emissions source of CH4 globally and in Canada. As part of ongoing efforts to mitigate CH4 emissions, it may be beneficial to obtain field scale flux estimates which can be used to verify CH4 emission factors. The objective of this study was to measure CH4 fluxes from a liquid dairy manure storage tank and compare measured fluxes with predicted values using US EPA methodology. Fluxes were measured from a circular concrete tank 11.25m in diameter storing liquid dairy manure in Bright, Ontario, Canada. Measurements were conducted semi-continuously from January through July 2003, using a tunable diode laser and the non-interfering micrometeorological mass balance method. Monthly average CH4 flux ranged from 11μg/m2/s in June after the tank had been emptied, to 153μg/m2/s in July. Large bubble flux events occurred in February and March that coincided with surface thawing. Predicted emissions using the US EPA approach with carryover of volatile solids showed overestimation unless a substantial correction factor was used. In contrast, if volatile solids were not carried over, predicted fluxes had acceptable agreement with measurements.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors: K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.