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

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

Isolation of ammonium bicarbonate by reactive distillation of food waste digestate liquor

Distillation is among the best techniques for management of ammoniacal nitrogen in anaerobic digestate; however, the suitability of the conventional system is neglected in favor of using more advanced setups. This investigation proves the reliability of the classical batch distillation apparatus for high throughput separation of solid crystals of ammonium bicarbonate from food waste digestate (FWD) liquor. Three replicates were carried out: 80 g of FWD liquor with a content of 50 g/L NH4HCO3 was processed for 7.5 h under minimum heating power (<60 °C) and 200 rpm to avoid excessive foam formation. After performing the reactive distillation, 81 % of NH4HCO3 was recovered as white solid crystals at the top of the distillation still. Although the distillation provided a solid material with the same structure and composition as those of the reagent-grade NH4HCO3, the stability of the isolated inorganic fertilizer was poorer, and it could lead to pollution swapping.

Bioelectrochemically-assisted ammonia recovery from dairy manure

The sustainability of direct land application of dairy manure is challenged by significant nutrient losses. Bioelectrochemical systems for ammonia recovery offer a manure management strategy that can recover both ammoniacal and organic nitrogen as a stable ammonia fertilizer. In this research, a microbial fuel cell (MFC) was used to treat two types of dairy manure under a variety of imposed anode compartment conditions. The system achieved a maximum coulombic efficiency of 20 ± 18 % and exhibited both COD and total nitrogen removals of approximately 60 %. Furthermore, the MFC showed a maximum organic nitrogen removal of 73.8 ± 12.1 %, and no differences in organic nitrogen (orgN) removal were detected among different conditions tested. Decreasing concentrations of anolyte ammonia nitrogen coupled with the observed orgN removal from the anolyte indicate that the MFC is effective at recovering orgN in dairy manure as ammoniacal nitrogen in the catholyte. Additionally, ion competition between NH4+ and other relevant cations (Na+, K+, and Mg2+) for transport across the CEM was investigated, with only K+ showing minor competitive effects. Based on the results of this research, we propose three key processes and two sub-processes that contribute to the successful operation of the MFC for nitrogen recovery from dairy manure. Bioelectrochemical systems for nitrogen recovery from dairy manure offer a novel, robust technology for producing a valuable ammonia nitrogen fertilizer, a thus far untapped resource in dairy manure streams.

In-vitro method and model to estimate methane emissions from liquid manure management on pig and dairy farms in four countries

Methane (CH4) emissions from manure management on livestock farms are a key source of greenhouse gas emissions in some regions and for some production systems, and the opportunities for mitigation may be significant if emissions can be adequately documented. We investigated a method for estimating CH4 emissions from liquid manure (slurry) that is based on anaerobic incubation of slurry collected from commercial farms. Methane production rates were used to derive a parameter of the Arrhenius temperature response function, lnA', representing the CH4 production potential of the slurry at the time of sampling. Results were used for parameterization of an empirical model to estimate annual emissions with daily time steps, where CH4 emissions from individual sources (barns, outside storage tanks) can be calculated separately. A monitoring program was conducted in four countries, i.e., Denmark, Sweden, Germany and the Netherlands, during a 12-month period where slurry was sampled to represent barn and outside storage on finishing pig and dairy farms. Across the four countries, lnA' was higher in pig slurry compared to cattle slurry (p < 0.01), and higher in slurry from barns compared to outside storage (p < 0.01). In a separate evaluation of the incubation method, in-vitro CH4 production rates were comparable with in-situ emissions. The results indicate that lnA' in barns increases with slurry age, probably due to growth or adaptation of the methanogenic microbial community. Using lnA' values determined experimentally, empirical models with daily time steps were constructed for finishing pig and dairy farms and used for scenario analyses. Annual emissions from pig slurry were predicted to be 2.5 times higher than those from cattle slurry. Changing the frequency of slurry export from the barn on the model pig farm from 40 to 7 d intervals reduced total annual CH4 emissions by 46 %; this effect would be much less on cattle farms with natural ventilation. In a scenario with cattle slurry, the empirical model was compared with the current IPCC methodology. The seasonal dynamics were less pronounced, and annual CH4 emissions were lower than with the current methodology, which calls for further investigations. Country-specific models for individual animal categories and point sources could be a tool for assessing CH4 emissions and mitigation potentials at farm level.

Circular bioeconomy approach for pig farming systems using microalgae-based wastewater treatment processes

The circular bioeconomy (CBE) presents a sustainable solution for the pig farming system, delivering economic and environmental benefits. This shift from a linear to a CBE model is anticipated to result in substantial economic, environmental, and social transformations. In this study, the CBE outcomes are evaluated with Scenarios (1 to 3): (1) pig farming and anaerobic digestion (AD) only, (2) pig farming, AD, and microalgae system (MS) with partial microalgae-based biomass (MB) recycle, and (3) pig farming, AD, and MS without MB recycle. Through economic and life cycle analyses, the internal rate of return for Scenarios (1 to 3) are 13.3%, 15.0%, and 12.3%, respectively, but the corresponding endpoint indicators are 483pt, 363pt, and 398pt. To address the best CBE, Scenario 2 by using MB product as a pig feed supplement could achieve higher revenue as well as lower environmental impact.

Data quantifying the behaviour of macro and trace elements along the feed - manure - treated waste continuum in pig production

Manure from animal production is commonly spread on agricultural soil as an organic fertiliser to provide macro and trace elements to crops. However, some trace elements can accumulate in the soil and become toxic to plants and microorganisms. These elements include copper (Cu) and zinc (Zn), which can be applied in large quantities when pig manure is spread. The feeding strategy and manure management (e.g. through treatment chains) are two mechanisms identified to better control the use of these elements, but their fate from the feed to the soil in pig production remains poorly documented. Better understanding the fate of Cu and Zn, as well as that of other trace and macro elements, along the feed - excreta - waste chain is required to develop alternative ways to reduce their environmental impacts. This dataset provides insight into the composition (Cu, Zn and other trace and macro elements) of organic products along two contrasting manure management chains: (1) only storage or (2) in-building separation, anaerobic digestion (AD) of solids, and digestate drying. Feed, raw slurry, liquid and solid phases after separation of the manure and AD products were sampled and then analysed to measure their total compound contents.

Impacts of subsidy for export of pig to domestic market on the spatial distribution of pig production and related nitrogen losses in China

The uneven distribution of pig production may create pollution hotspots and severe environmental costs at the local level; however, there is little information available about the socioeconomic driving forces behind the spatial distribution of pig production and its potential environmental costs. Here, we collected time series data (1990, 2012 and 2017) of pig production and multiple socioeconomic indicators from 2333 counties in China to remedy this knowledge gap. Our results indicate that, the poverty level, pork self-sufficiency rate, feed availability per head and environmental pollution risk were all played negligible roles in determining the spatial distribution of pig production at the county level in China between 1990 and 2017. The spatial distribution of pig production was more impacted by the so-called subsidy policy for export of pig to domestic market (hereinafter called pig subsidy policy), which aimed to subsidize counties exporting large amounts of pigs to other counties. In 2017, approximately 181 million head of pig was exported to domestic market from subsidized counties, and these counties received a subsidy amount of US$ 450 million. However, the total environmental cost, considering the human health, ecosystem and climate change damages of nitrogen losses of the pigs exported to domestic market, was US$ 4.5 billion, 10 times of the subsidy. If all the subsidies were fully designated to reduce ammonia emissions from the industrial pig production, the total cost could be reduced by US$ 1.6 billion; however, this was not enough to cover all the damage. Overall, the spatial distribution of pig production was strongly impacted by the pig subsidy policy in China. Applying $400 million of pig subsidy to ammonia emissions reduction could reduce external environmental costs by 31 % and deliver $1.3 billion in socioeconomic benefits. The total subsidy needs to be increased and used smartly in the future to reduce nitrogen losses from the production chain.

Spatial patterns in pollution discharges from livestock and poultry farm and the linkage between manure nutrients load and the carrying capacity of croplands in China

The rapid development of livestock and poultry farming in China has resulted in an increasing threat of water pollution. In particular, mitigating livestock-related pollutant discharges is a key issue for environmental sustainability, especially for inland surface water bodies. In order to ensure the effective control of pollution and the efficient utilization management of livestock manure, spatially explicit surveys of pollutant generation and discharge from the livestock sector must be performed. In the present study, we estimated the grid cell-level distributions in the generation and discharge of four typical pollutants (chemical oxygen demand, ammonium nitrogen, total nitrogen and total phosphorus) from the livestock sector across the country with a spatial resolution of 30 arc-seconds. The distributions were estimated using the most recent pollution source census data and multi-sourced ancillary materials by a dasymetric mapping approach. We further investigated the feasibility of the resource utilization of livestock manure by comparing manure-source nutrients with the carrying capacity of adjacent croplands. Our results show that low-intensive farming generated and discharged the majority of livestock farming pollution, with other cattle and pigs breeding identified as the two major sources of pollution from the livestock sector. Southwest, Central and East China suffered the highly densified pollutants generation and discharges. Furthermore, cropland exceeding its carrying capacity was concentrated in these regions. Our findings provide additional insights into livestock and poultry farming in the context of relocation, strengthening regulation, transforming breeding operations, and rationalizing the resource use of manure, all of which are important measures for the sustainable development of both agriculture and the environment.

Prevention of human exposure to livestock faecal waste in the household: a scoping study of interventions conducted in sub-Saharan Africa

BACKGROUND

Poorly managed animal faecal waste can result in detrimental environmental and public health implications. Limiting human exposure to animal waste through Animal inclusive Water Sanitation and Hygiene (A-WASH) strategies is imperative to improve public health in livestock keeping households but has received little attention to date. A small number of A-WASH interventions have previously been identified through a systematic review by another research team, and published in 2017. To inform intervention design with the most up-to-date information, a scoping study was conducted to map the existing evidence for A-WASH in sub-Saharan Africa (SSA) emerging since the previous review.

METHODS

This review followed PRISMA guidelines to identify interventions in SSA published between January 2016 to October 2022. Databases searched included PubMed, PMC Europe, CabDirect and Web of Science. Studies were eligible for inclusion if they were written in English and documented interventions limiting human contact with animal faecal material in the SSA context. Key data extracted included: the intervention itself, its target population, cost, measure of effectiveness, quantification of effect, assessment of success, acceptability and limitations. These data were synthesized into a narrative, structured around the intervention type.

FINDINGS

Eight eligible articles were identified. Interventions to reduce human exposure to animal faecal matter were conducted in combination with 'standard' human-centric WASH practices. Identified interventions included the management of human-animal co-habitation, educational programs and the creation of child-safe spaces. No novel A-WASH interventions were identified in this review, beyond those identified by the review in 2017. Randomised Controlled Trials (RCTs) were used to evaluate six of the eight identified interventions, but as effect was evaluated through various measures, the ability to formally compare efficacy of interventions is lacking.

CONCLUSION

This study indicates that the number of A-WASH studies in SSA is increasing and the use of RCTs suggests a strong desire to create high-quality evidence within this field. There is a need for standardisation of effect measures to enable meta-analyses to be conducted to better understand intervention effectiveness. Evaluation of scalability and sustainability of interventions is still lacking in A - WASH research.

Fate of veterinary antimicrobials in Canadian prairie soils - A critical review

Veterinary antimicrobials (VAs) widely used in intensive livestock production are excreted in livestock manure. Manure is an essential component in agriculture for recycling critical nutrients and improving overall soil health. However, manure application on agricultural lands increases the risk of contaminating the ecosystem with antimicrobials. Antimicrobials in manure-amended soils can affect ecosystem functioning via their negative effect on biogeochemical cycles and increase human exposure. Also, the release of antimicrobials to the broader environment, including that arising because of offsite transport, is linked to the global increase in antibiotic resistance in bacteria. Antibiotic resistance is an emerging global threat to human health, particularly the pathogenic bacteria resistant to the main antimicrobial classes in use. Therefore, there is a need to review current literature to enhance our understanding of the fate of these contaminants across agricultural landscapes. This review focuses on (1) a detailed discussion of sorption mechanisms by exploring the structural attributes of antimicrobials, (2) specific sorption interactions with active adsorbent components in the soil as these comprehensive data are important to identify the sorption strengths of antimicrobials which control their fate in the ecosystem, and (3) the effects of on-farm management practices on VA transport and is focused on manure amendment and tillage practices. The key facts identified in this review are critical to identifying sustainable on-farm management practices to enhance the productivity of arable agricultural lands in Canada and across the globe while minimizing the risk of offsite transport of VAs. Further, the research gaps highlighted in the relevant sections are important to designing future research in Canada and globally under similar to variable land/farm management practices.

Farm biogas project considering carbon trading indicates promising economic results-a case study

The application of the farm biogas project is a perfect measure to deal with the increasingly nervous global climate problem and energy crisis and can support the accomplishment of urgently needed carbon peaking and carbon neutrality effectively. But the poor economic benefits hinder its better development. Thus, this paper aims to enhance the economics of farm biogas projects and explore a win-win model for economic and environmental benefits by studying the economic impact of participation in carbon trading on three types of farm biogas projects. First, economic analysis of farm biogas projects based on life cycle cost is carried out using case analysis. Second, the greenhouse gas emission reductions are calculated and benefits from carbon trading are considered. Then, the economic robustness was tested. Specifically, the economics of all three types of farm biogas projects is improved after carbon trading. The ecological farm biogas project has the best economic performance, with a net present value of $551,689.11, internal rate of return of 49%, and payback period of 2.39 years. In addition, the emission reductions of 5045.79 t CO₂e, 7420.28 t CO₂e, and 148.41 t CO₂e are very significant. Based on these, suggestions for developing farm biogas projects and introducing biogas projects to carbon trading are put forward for the reference of governments and investors when making investments and reforms. According to the result, participation of farm biogas projects in carbon trading can effectively enhance economic benefits and accelerate the achievement of the greenhouse gas emission reduction target which is of great significance to the urgent goal of global green and low-carbon transformation.

Methane release from enteric fermentation and manure management of domestic water buffalo in Nepal

Methane (CH₄) emission in livestock arises from enteric fermentation (EnF) and manure management (MM). This study develops the country-specific CH₄ emission factors (EFs) in both EnF and MM for domestic water buffalo (Bubalus bubalis) and estimates total CH₄ emission in Nepal using Intergovernmental Panel on Climate Change (IPCC) Tier 2 methodology. Seasonal field data were collected on morphological characteristics, feed characteristics, and manure management practices of the buffalo. The buffalo population was divided into five age groups, and at least 35 buffalo individuals were measured from each age group in the Hilly and Plain regions of Nepal in the winter and summer seasons. Buffalo adult male (BAM) had the highest body weight of 530 ± 53 kg in the plain region and 514 ± 65 kg in the Hill region. Similarly, the weight of buffalo calf (BC) was 91 ± 25 kg in the plain region and 77 ± 26 kg in the Hill region. For different age groups of buffalo, EnF EFs ranged from 34 ± 8 to 90 ± 10 kg CH₄ head^-1 year^-1 and MM EFs ranged from 2.5 ± 0.5 to 7.5 ± 0.5 kg CH₄ head^-1 year^-1. The estimated EnF and MM EFs of buffalo were not statistically different by region (p > 0 .05). The total CH₄ flux from buffalo was 347.8 Gg year^-1 in Nepal, contributing 322.2 Gg year^-1 from EnF and 25.6 Gg year^-1 from MM. The country-specific EFs are highly recommended for precise computing of the national emissions and carrying out mitigation action.

Acidification of slurry to reduce ammonia and methane emissions: Deployment of a retrofittable system in fattening pig barns

Livestock farming, and in particular slurry management, is a major contributor to ammonia (NH₃) and methane (CH₄) emissions in Europe. Furthermore, reduced NH₃ and CH₄ emissions are also relevant in licensing procedures and the management of livestock buildings. Therefore, the aim is to keep emissions from the barn as low as possible. Acidification of slurry in the barn can reduce these environmental and climate-relevant emissions by a pH value of 5.5. In this study, an acidification technology was retrofitted in an existing fattening pig barn equipped with a partially slatted floor. The slurry in a compartment with 32 animals was acidified. An identical compartment was used for reference investigations (case-control approach). Several times a week slurry was pumped for acidification in a process tank outside the barn compartment in a central corridor, where sulphuric acid (H₂SO₄) was added. Then the slurry was pumped back into the barn. In contrast to other systems, where acidified slurry was stored mainly in external storage tanks, in this study the slurry was completely stored in the slurry channels under the slatted floor, during the entire fattening period. The emission mass flow of NH₃ and CH₄ was measured continuously over three fattening periods, with one period in spring and two periods in summer. On average 17.1 kg H₂SO₄ (96%) (m³ slurry)^-1 were used for acidification during the three fattening periods. NH₃ and CH₄ emissions were reduced by 39 and 67%, respectively. The hydrogen sulphide (H₂S) concentration in the barn air of the acidification compartment was harmlessly low (0.02 ppm). Thus, despite the storage of the acidified slurry in the barn, the system leads to a lower concentration of detrimental gases, which is beneficial for the animals' as well as for the workers' health. The study shows that it is possible to retrofit acidification technology into existing pig barns. Further investigations shall identify possible measures to reduce the amount of H₂SO₄ used and thus minimise the sulphur input into the slurry.

Assessing Self-reported Occupational Hazards of Manure Applicators in the Upper Midwest

Manure management on farms presents potential risks to human health and safety, including infectious, chemical, and physical exposures that may result in injury or fatality. Toxic gases and confined spaces are among the most common hazards. These hazards are especially salient for the Upper Midwest of the United States. This study characterizes the occupational health and safety practices and experiences of manure applicators in Minnesota. This cross-sectional study surveyed 162 commercial manure applicators about their work characteristics, safety practices, and health and safety experiences. Respondents reported an average of 17 hours per day applying manure during the busy season, which typically occurs several weeks each year. One hundred and thirty-one (90%) of 145 respondents did not regularly use gas monitors during application. Thirty-three (37%) of 90 respondents reported at least one symptom of gas exposure during manure application work. Those that worked with swine manure were more likely to report symptoms of gas exposure than those who did not work with swine (OR 9.5; CI: 2.0, 89.0). Those that had entered confined spaces were more likely to report symptoms of gas exposure than those who had not entered confined spaces (OR 4.4; CI: 0.1, 1.1). Fourteen (9%) of 150 respondents reported being injured when applying manure. Manure work can be hazardous and may be associated with injury and gas exposure. These findings offer a starting point for future research and intervention to protect and improve the health and safety of applicators.

Dis-adoption of small-scale biogas plants in Vietnam: what is their fate?

Biogas production at a small-scale level through anaerobic digestion has been promoted in Vietnam as an appropriate technology for cooking and animal waste management within rural households. Despite the large number of small-scale biogas plants being built, there is an increase in the reported cases of their dis-adoption. This study attempts to present the state of the art of biogas plants' abandonment issue and reveal the fate of biogas plants. The primary data were collected in Thua Thien Hue province in central Vietnam among owners of small-scale biogas plants selected with the purposive sampling technique. Methods included semi-structured interviews with respondents who abandoned their biogas technology (at least 6 months before the primary data collection) (n = 37) and with respondents who continually use it (n = 62). SPSS 25 IBM was used for the binary logit model with 6 independent variables. Using a logistic regression analysis of various cross-sectional data, key forces were uncovered to determine the factors that can influence the abandonment of biogas technology. Results showed that households with more members working on the farm and those more satisfied with the biogas plant maintenance are less likely to abandon it. Respondents provided the information that their biogas plants mainly were not used for any other purpose after dis-adoption (excepting biogas plants used for further storage of human excreta because they were connected to toilets).

Effects of different treatments of manure on mitigating methane emissions during storage and preserving the methane potential for anaerobic digestion

Current agricultural practices in regards to storage of manure come with a significant GHG contribution, due, to a big extent, to CH₄ emissions. For example, in Denmark, the agricultural sector is responsible for about 11.1 metric tons of CO₂ equivalents; only about 0.2 metric tons come directly from CO₂, while 6.0 tons come from CH₄. The present study aims at evaluating and comparing two methods based on their effect on suppressing CH₄ emissions during storage as well as on preserving and enhancing CH₄ yield in a subsequent anaerobic digestion step: the commonly applied acidification with H₂SO₄ as acidifying agent and thermal treatment at the mild temperatures of 70 and 90 °C (pasteurization). Although both treatments effectively suppressed CH₄ emissions during storage, they exhibited a significant difference in preserving and/or enhancing the CH₄ potential of manure. Specifically, thermal treatment resulted in 16-35% enhancement of CH₄ potential, while acidification resulted in decreasing the CH₄ yield by 6-23% compared to non-treated manure. Further investigation showed that storage itself positively affected the CH₄ potential of treated manure in a subsequent anaerobic digestion step; this was attributed to microbial activity other than biomethanation during storage. In overall and based on the results obtained regarding suppression of CH₄ emissions during storage as well as CH₄ potential enhancement, pasteurization at the temperatures tested is a promising alternative to the broadly applied acidification of manure.

Assessment of livestock greenhouse gases in Colombia between 1995 and 2015

The livestock sector in Colombia significantly participates in national economic dynamics but makes significant worldwide contributions to greenhouse gas emissions. Hence, climate change mitigation in this sector is essential. This study aims to assess the greenhouse gas in the livestock sector. The results are reported in methane emissions (CH₄) and nitrous oxide (N₂O) from enteric fermentation, and N₂O by manure management based on the information from the Emission Database for Global Atmospheric Research (EDGAR), in all cases expressed as dioxide of carbon (CO_2eq). The emissions obtained from the EDGAR database for 2015 were proportional to the values of the National Inventory of Greenhouse Gases published by the Institute of Hydrology, Meteorology, and Environmental Studies (IDEAM) in 2016. Colombia is the 12th on global, 4th in America and 2nd in South America position by livestock GHG emission, and is the dominant source in all economic sector. The results showed higher records for CH₄ emissions during the years 2010 and 2015, while the N₂O emissions were higher during 2015. The regions with the highest emissions of CH₄ and N₂O corresponded to the northwestern area of Colombia. The Spearman correlation test showed a positive correlation between the CH₄ emissions, and the age groups studied. The post hoc analysis of the Kruskal-Wallis test showed a more significant influence on CH₄ emissions.

Redeploy manure resources to enhance the agro-pastoral cycle

Returning manure to the land is a critical link in the internal cycle of agricultural systems, but excess manure leads to water eutrophication. The traditional manure re-use method brings pathogenic microorganisms, heavy metals, antibiotic resistance genes (ARGs), insect eggs, and other contaminants into the soil, posing a great threat to the ecological environment and human health. Clarifying the spatial distribution patterns of manure nutrient supply and farmland nutrient demand can help guide a more efficient and harmless way to return manure to farmland. This work counted data on cultivation and breeding in 356 cities on the Chinese mainland from 2015 to 2019 and calculated the livestock breeding volume (LB), total environmental capacity (C), and remaining environmental capacity (RC) accordingly. The Spatial Autocorrelation Model (SAC) was used to analyze the distribution patterns of the three. Data results show that China currently has the potential to double LB, but most cities in the west have excess manure due to the mismatched distribution of LB and C. The hot spot analysis results demonstrate the priority/general areas of manure management and the export/import areas of manure resources. The results of the outlier analysis show that some cities located at the boundary of RC Cold/Hot spot areas (e.g., Chengdu City) can perform resource replacement nearby to relieve local environmental pressure. This study analyzes the potential and realistic resistance to utilizing manure as an organic nutrient resource and provides a reference for developing manure management links.

Methane emissions from five Danish pig farms: Mitigation strategies and inventory estimated emissions

This study investigated whole-farm methane emissions from five Danish pig farms with different manure management practices and compared measured emission rates to international and national greenhouse gas inventory emission models. Methane emissions were quantified by using the tracer gas dispersion method. Farms were measured between five and eight times throughout a whole year. One of the farms housed sows and weaners (P1) and the others focused on fattening pigs (P2-P5). The farms had different manure treatment practices including biogasification (P3), acidification (P4-P5) and no manure treatment (liquid slurry) (P1-P2). Quantified methane emissions ranged from 0.2 to 20 kg/h and the highest rates were seen at the farms with fattening pigs and with no manure treatment (P2), while the lowest emissions were detected at farms with manure acidification (P4 and P5). Average methane emission factors (EFs), normalised based on livestock units, were 14 ± 6, 18 ± 9, 8 ± 7, 2 ± 1 and 1 ± 1 g/LU/h, for P1, P2, P3, P4 and P5, respectively. Emissions from fattening pig farms with biogasification (P3) and acidification (P4-P5) facilities were 55% and 91-93% lower, respectively, than from farm with no manure treatment (P2). Inventory models underestimated farm-measured methane emissions on average by 51%, across all models and farms, with the Danish model performing the worst (underestimation of 64%). A revision of model parameters related to manure emissions, such as the estimation of volatile solids excreted and methane conversion factor parameters, could improve model output, although more data needs to be collected to strengthen the conclusions. As one of the first studies assessing whole-pig farm emissions, the results showed the potential of the applied measuring method to identify mitigation strategy efficiencies and highlighted the necessity to investigate inventory model accuracy.

Impact of slurry removal frequency on CH4 emission and subsequent biogas production; a one-year case study

Anaerobic digestion of animal slurry to produce biogas is the dominated treatment approach and a storage period is normally applied prior to digestion. Pre-storage, however, contributes to CH₄ emissions and results in loss of biogas potential. Manure management was found to be an efficient approach to reduce not only the on-site CH₄ emission but may also have extended influence on CH₄ emission/losses for storage and subsequent biogas process, while the connection remains unclear. The objective of this study was therefore to evaluate the impact of slurry management (e.g. removal frequency) on CH₄ emission (both on-site and storage process prior to biogas) and biogas yield. An experimental pig house for growing-finishing pigs (30-110 kg) and the relevant CH₄ emission was monitored for one year. In addition, the specific CH₄ activity (SMA) test was conducted and used as an alternative indicator to reflect the impact. Results showed that the manure management affected both on-site and subsequent methane emission; with increased manure removal frequencies, the methane emission became less dependent on variation of temperatures and the specific methanogenesis activity was significantly lower. The highest SMA (100 mL CH₄ gVS^-1), for instance, was observed from the slurries with limited emptied times, which was 10 times of that from the slurries being emptied three times a week. These findings could enlighten the development of environmentally friendly strategies for animal slurry management and biogas production.

Effects of different conditions tested "in vitro" on the phosphorus runoff potential of livestock manure

This study aimed to investigate the changes of swine and dairy manure characteristics during a long-term storage (150-180 days) under 4 °C, 20 °C, and 37 °C, sealed and unsealed conditions. Water extractable phosphorus (WEP) of both manures rapidly increased during the first 15-30 days and then decreased. At the end of the storage, the WEP reduction was 90%±3% and 71%±5% of the initial concentration for swine manure and dairy manure, respectively. Generally, unsealed storage and higher temperatures led to more WEP reduction. This study suggested that manure stored for less than 30 days had the highest P runoff potential, while a long-term manure storage reduced P runoff potential compared to freshly excreted manure.

Cooperation between specialized livestock and crop farms can reduce environmental footprints and increase net profits in livestock production

The rapid specialization of livestock production in China has contributed to spatially decoupled crop and livestock production, leading to various environmental pollution issues. Some regional agro-environmental policies have recently promoted the coupling of specialized crop and livestock farms through cooperation. However, the environmental and economic performances of such cooperation remain unclear. This study investigated multiple environmental footprints of two contrasting production systems: cooperative crop-livestock systems (CCLS) and decoupled specialized livestock systems (DSLS), using survey data of 87 ruminant farms in Northwest China. Results show that farms in CCLS had lower net greenhouse gas (GHG) emissions (12-29%), lower reactive nitrogen (Nr) emissions (21-40%), lower phosphorus footprints (PF) (41-54%), and used less cropland (24-31%) per kg animal product, compared to those in DSLS. The large differences in GHG emissions between the two systems were mainly related to enteric fermentation and resource production (used for feed production). The differences in Nr emissions and PF were mainly related to manure management. Net profits per kg animal product were higher in CCLS (13-35%) than in DSLS, and most profits originated from lower purchasing costs of feed and young livestock. Net profits and environmental footprints were negatively correlated, suggesting an environmental and economic win-win situation for CCLS. The possible obstacles to recoupling specialized crop and livestock farms through cooperation have been discussed, including farm size, contract stability, and local policies. Our study provides science-based evidence to support policymakers and specialized farms to close nutrient loops between crop and livestock production sectors through regional cooperation.

Nitrogen budgets of contrasting crop-livestock systems in China

The crop-livestock system is responsible for a large proportion of global reactive nitrogen (Nr) losses, especially from China. There are diverse livestock systems with contrasting differences in feed, livestock and manure management. However, it is not yet well understood which factors greatly impact on the nitrogen (N) budgets and losses of each system. In this study, we systematically evaluated the N budgets of the crop-livestock production system from 1980 to 2050 in China by identifying the differences of 20 distinct livestock systems. During 1980 to 2010, the total N flow through the crop-livestock system increased from 21.4 to 49.7 Tg, with large variations in different input/output pathways, due to the strong livestock transitions of production towards to a monogastric and landless industrial system. Different systems contributed differently to the total N budgets in 2010. For example, the landless industrial system contributed 67% of livestock product N output, but accounted for 80% of total mineral N fertilizer use and feed N imports by the whole crop-livestock system. The mixed system had the highest rate of N use efficiency at system level due to high dependence on recycled N. N losses were diversely distributed by different systems, with the mixed ruminant system responsible for the majority of NH₃-N emission in livestock production, and the grazing ruminant system dominant in NO₃-N losses in feed production. The total N entering the crop-livestock system is estimated to be 53.9 Tg with total N losses of 41.3 Tg in 2050 under a business-as-usual scenario. However, this amount could be significantly decreased through combined measures that indicate a considerable potential for future improvements. Overall, our results provide new insights into N use and the management of livestock production.

Survey on storage, application and incorporation practices for organic fertilizers in Germany

Organic fertilizers from animal production might contain undesirable components, such as veterinary medical product (VMP) residues, that are released into the environment during application. In addition to measures to reduce the use of VMPs through animal health measures, manure management could be an expedient strategy to prevent VMPs from entering the environment. The quantity applied is mainly determined by the nitrogen content. In addition, the depth of incorporation into the soil plays a major role in the environmental risk assessment of VMPs. The new regulations of the German fertilizer ordinance (DüV, 2020), which came into force at the beginning of 2020, as well as the changes that have not yet been fully implemented, will result in adjustments to the storage, application and incorporation practices for organic fertilizer. The aim of this study was to gain more information about the practice of storage, application and incorporation and the challenges for farmers in Germany. An online survey among farmers was conducted to determine the status quo. Almost all of the 125 participants kept livestock, predominantly cattle (68%) and pigs (33%). A third of participants (30%) needed a temporary storage site, for example at neighboring farms. Of the participants, 81% (n = 125) owned cropland and/or grassland. On cropland, manure was mostly incorporated at a depth of 3-15 cm, whereas on grassland, it was mostly applied superficially. On grassland lower-emission application techniques such as slot drill or injector procedures have so far rarely been used. The survey results provided important insights about storage, application and incorporation practices for organic fertilizers in Germany which could be used for the calculation of predicted environmental concentrations (PEC) as part of the environmental risk assessments of veterinary pharmaceuticals.

A review targeting veterinary antibiotics removal from livestock manure management systems and future outlook

Veterinary antibiotics (VAs) contamination has been considered as a worldwide environmental and health concern in recent decades. This paper reviewed the variability of contents of VAs and their release from the animal breeding industry into the surrounding environment along with the performance of the manure treatment technologies. The data collected revealed that VAs were mostly excreted in animal feces and observed in manure, soil, water, and sediment. The findings illustrate the disparity of VAs in excretion rates, consumption, and their residues in the environment with relatively high distribution for tetracyclines, fluoroquinolones, and sulfonamides. Anaerobic digestion has a capacity to remove of 73% VAs while manure composting and constructed wetlands can remove 84.7%, and 90% VAs. Due to the profound effect of antibiotics on the environment, further research and intensive management strategies for livestock manure need to be designed to improve the removal efficiency and manure management technologies.

Particle fractionation controls Escherichia coli release from solid manure

Bacteria transport through soil is a complex process particularly when the cells are released from solid manures and co-transported with particles. This study focuses on understanding of the Escherichia coli release from different particle fractions (0.25-, 0.5-, 1-, and 2-mm) of solid manure and evaluating different influent boundary conditions during cell release from manure and when a solid manure is applied to the soil. The 0.25-mm and 2-mm particle sizes resulted a greater cell release compared to 0.5-mm and 1-mm fractions (p < 0.05). The shape and magnitude of the cell release curves (CRCs) from the original manure bulk were mainly influenced by the two 0.25-mm and 2-mm fractions, respectively. The arithmetic mean for normalizing the CRCs and the time variable- based normalized CRCs for the manure-treated soil were the robust variables in evaluation of the experimental data. However, a single maximum bacteria concentration could provide the realistic dataset for the modeling process. Evaluation of the root-mean-squared-error and Akaike criterion showed that the two- and three-parametric models are recommended for simulating the cell release from solid manure in comparison with one parametric models. This study also suggests considering separate microbial release evaluations, with regards to influent concentration, for manure and manure-treated soils to propose best management practices for controlling bacteria pollution. Further research will reveal the key roles of different woody components and soluble material ratios for the various solid manures in bacteria release.

Environmental burdens of small-scale intensive pig production in China

Small-scale intensive pig production systems account for over a half of the total number of pig farms in China, of which concerns have been raised relating to their environmental performances. This study explores the cradle-to-slaughterhouse gate environmental impacts using life cycle assessment (LCA) approach, with the purpose of identifying major hotspots to formulate mitigation strategies. The functional unit is defined as 1000 kg of pig carcass weight. Consistent with previous research, feed production makes up the largest contribution (56-95%) to all the six selected impact categories based on the ReCiPe 2016 framework. Of the feed ingredients, maize is identified as the principal hotspot mainly due to the large consumption as well as the heat usage in grain steaming to enhance availability of starch digestion. The results also indicate that changes of feed consumption and composition along the lifetime growth reveal a much higher contribution from the grower-finisher stage. Marked differences are observed in terms of greenhouse gas emissions from pig production between developing (including China) and developed countries. With lots of studies showing feasibilities, improvements suggested for small-scale intensive pig production systems include the optimization of feed formulas, the introduction of new feed technologies, and the upgrade of manure management system. Our results provide valuable and practical insight for the Chinese pig supply chain to mitigate environmental burdens and achieve future environmental sustainability.

Provincial cattle carbon emissions from enteric fermentation and manure management in South Africa

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.

Functional relationship of particulate matter (PM) emissions, animal species, and moisture content during manure application

Livestock manure is recycled to agricultural land as organic fertilizer. Due to the extensive usage of antibiotics in conventional animal farming, antibiotic-resistant bacteria are highly prevalent in feces and manure. The spread of wind-driven particulate matter (PM) with potentially associated harmful bacteria through manure application may pose a threat to environmental and human health. We studied whether PM was aerosolized during the application of solid and dried livestock manure and the functional relationship between PM release, manure dry matter content (DM), treatment and animal species. In parallel, manure and resulting PM were investigated for the survival of pathogenic and antibiotic-resistant bacterial species. The results showed that from manure with a higher DM smaller particles were generated and more PM was emitted. A positive correlation between manure DM and PM aerosolization rate was observed. There was a species-dependent critical dryness level (poultry: 60% DM, pig: 80% DM) where manure began to release PM into the environment. The maximum PM emission potentials were 1 and 3 kg t^-1 of applied poultry and pig manure, respectively. Dried manure and resulting PM contained strongly reduced amounts of investigated pathogenic and antibiotic-resistant microorganisms compared to fresh samples. An optimal manure DM regarding low PM emissions and reduced pathogen viability was defined from our results, which was 55-70% DM for poultry manure and 75-85% DM for pig manure. The novel findings of this study increase our detailed understanding and basic knowledge on manure PM emissions and enable optimization of manure management, aiming a manure DM that reduces PM emissions and pathogenic release into the environment.

Mitigation potential for carbon and nitrogen emissions in pig production systems: lessons from the North China Plain

China produces approximately half of the world's pork at a high environmental cost. Implementing mitigation measures requires a better understanding of pig farming systems that are often diverse in practice. Nutrient uses and losses can be largely altered due to these variations but have not, however, been fully evaluated; moreover, attention is rarely paid to pollution swapping. Our study evaluated carbon (C) and nitrogen (N) flows among pig farms on the North China Plain using the mass flow approach. The impacts of advanced mitigation measures on nitrogen use efficiency (NUE) and on C and N emissions were further analyzed via scenario analyses. The results showed that large variations among farms were observed by comparing the best-performing farms ("top 20%") with the "other" farms; the comparisons showed 31.3 vs. 21.3% for the system NUE, 3.0 vs. 5.7 kg N ·100 kg liveweight gain (LWG)^-1 for manure N losses, and 108.1 vs. 146.4 kg CO₂-eg·100 kg LWG^-1 for greenhouse gas (GHG) emissions, respectively. Lower system NUE was caused by lower NUEs of pigs, followed by high N emissions from manure and excessive manure application. Scenario analyses indicated that the total N loss of systems can be mitigated by 10-13% through dietary manipulation and by 26%, 27%, and 13% by low-emission storage, biogas production with improved storage, and balanced fertilization, respectively. Anaerobic digestion was solely effective for GHG mitigation (46% reduction), but no impacts were observed for all other low-NH₃ measures. Combining mitigation measures simultaneously decreased total N and GHG losses by 56% and 54%, respectively, and increased the system NUEs by 89%. The wide variations among farms suggest largely attainable improvements in productivity and nutrient use by closing the management gaps related to these factors. Proper combinations of advanced measures are further needed to achieve more effective mitigation goals for multiple pollutants.

Manure anaerobic digestion effects and the role of pre- and post-treatments on veterinary antibiotics and antibiotic resistance genes removal efficiency

This review was aimed to summarize and critically evaluate studies on removal of veterinary antibiotics (VAs), antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) with anaerobic digestion (AD) of manure and demonstrate areas of focus for improved removal efficiency. The environmental risks associated to the release of the same were also critically evaluated. The potential of AD and advanced AD of manure on removal rate of VAs, ARGs and MGEs was thoroughly assessed. In addition, the role of post and pre-AD treatments and their potential to support VAs and ARGs removal efficiency were evaluated. The overall review results show disparity among the different groups of VAs in terms of removal rate with relatively higher efficiency for β-lactams and tetracyclines compared to the other groups. Some of sulfonamides, fluoroquinolones and macrolides were reported to be highly persistent with removal rates as low as zero. Within group differences were also reported in many literatures. Moreover, removal of ARGs and MGEs by AD was widely reported although complete removal was hardly possible. Even in rare scenarios, some AD conditions were reported to increase copies of specific groups of the genes. Temperature pretreatments and temperature phased advanced AD were also reported to improve removal efficiency of VAs while contributing to increased biogas production. Moreover, a few studies also showed the possibility of further removal by post-AD treatments such as liquid-solid separation, drying and composting. In conclusion, the various studies revealed that AD in its current technological level is not a guarantee for complete removal of VAs, ARGs and MGEs from manure. Consequently, their possible release to the soils with digestate could threaten the healthcare and disturb soil microbial ecology. Thus, intensive management strategies need to be designed to increase removal efficiency at the different manure management points along the anaerobic digestion process.

Swine slurry characteristics as affected by selected additives and disinfectants

Current swine industry practice is to house animals in confinement facilities which capture and store feces and urine as slurry in pits below the production area. Additives and disinfectants may be introduced into the manure pits. This study was conducted to measure the effects of additives and disinfectants on temporal changes in swine slurry characteristics. Slurry from a commercial swine production facility in southeast Nebraska, USA was collected and transferred to 57 L reactors located within a greenhouse. Selected additives and disinfectants were added to the reactors and physical properties, chemical characteristics, and antibiotic concentrations were monitored for 40 days. Concentrations of dry matter (DM), total nitrogen (TN), phosphorus pentoxide (P₂O₅), calcium (Ca), magnesium (Mg), zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu) were significantly greater than the Control in each of the reactors containing additives. The reactors in which the additives MOC-7, More Than Manure®, Sludge Away, and Sulfi-Doxx were introduced had significantly greater values of chemical oxygen demand (COD), total volatile solids (TVS), total suspended solids (TSS), total solids (TS), dry matter (DM), TN, P₂O₅, Ca, Mg, Zn, Fe, Mn, Cu and chlortetracycline than the other additive treatments. Concentrations of TVS and TSS were significantly lower in the reactors containing Clorox® and Virkon™ than the other disinfectant treatments. The total dissolved solids (TDS) concentration of 26,500 mg L^-1 and pH value of 7.27 obtained for the reactors containing Tek-Trol were significantly greater than measurements obtained for the other treatments. Concentrations of chlortetracycline and tiamulin of 8840 and 28.8 ng g^-1, respectively, were significantly lower for the treatments containing Tek-Trol. The sodium (Na) concentration of 1070 mg L^-1 measured in the reactors containing Clorox® was significantly greater than values for the other disinfectant treatments. The introduction of selected additives and disinfectants may influence certain physical properties, chemical characteristics, and antibiotic concentrations of swine slurry.

The potential of Turkey's province-based livestock sector to mitigate GHG emissions through biogas production

Methane and nitrous oxide are the two leading greenhouse gases (GHG) that are released to the atmosphere due to livestock enteric fermentation and manure management. This study examines Turkey's province-based GHG emissions released by its livestock sector due to these processes. Besides, this study focusses on biogas production through anaerobic digestion, which is one of the most effective GHG mitigation options from manure management. This study aims to show the importance of the livestock sector in regards to GHG emissions in Turkey based on estimations made by the Intergovernmental Panel on Climate Change (IPCC) 2006 Guidelines. As a result of these estimations, for the year 2015, 33.85 million tons of carbon dioxide equivalent (CO₂-eq) were produced from enteric fermentation and manure management system. The study also aims to evaluate Turkey's province-based biogas production potential from animal manure through the anaerobic digestion (AD) technology. Two different biogas potential scenarios with varying manure recovery rates were developed. Scenario 1 was developed based on the assumption of that total amount of produced animal manure would be used in AD for biogas production, and scenario 2 was developed based on the realistic manure recovery rates that vary with the type of livestock. Biogas potentials for scenario 1 and scenario 2 were determined as 8.41 billion m³ and 4.18 billion m³ in 2015, respectively. These values can meet Turkey's total electricity demand at a rate of 5.25% for scenario 1, and the rate of 2.3% for scenario 2. In addition, according to Turkey's GHG Inventory, submitted annually to the United Nations Framework Convention on Climate Change (UNFCCC), GHG emissions from manure management can be reduced by 1.13% through biogas production.

How to avoid coastal eutrophication - a back-casting study for the North China Plain

Eutrophication is a serious problem in Chinese seas. We explore possibilities to avoid coastal eutrophication without compromising food production in the North China Plain. We used the Model to Assess River Inputs of Nutrient to seAs (MARINA 1.0) for back-casting and scenario analysis. Avoiding coastal eutrophication by 2050 implies required reductions in river export of total nitrogen (TN) and phosphorus (TP) by 50-90% for the Hai, Huai and Huang rivers. We analyzed the potential to meet these targets in 54 scenarios assuming improvements in manure recycling, fertilizer application, animal feed and wastewater treatment. Results indicate that combining manure recycling while reducing synthetic fertilizer use are effective options to reduce nutrient inputs to seas. Without such options, direct discharge of manure are important sources of water pollution. In the 7-25 scenarios with the low eutrophication potential, 40-100% of the N and P in untreated manure is recycled on land to replace synthetic fertilizers. Our results can support the formulation of effective environmental policies to avoid coastal eutrophication in China.

Substituting organic manure for compound fertilizer increases yield and decreases NH3 and N2O emissions in an intensive vegetable production systems

Substituting organic manure for compound fertilizer may play an important role in regulating the nitrogen (N) cycle and consequently affecting crop yield in agroecosystems. However, how substituting different organic manures for compound fertilizer affects crop yield and ammonia (NH₃) and nitrous oxide (N₂O) emissions in the vegetable system during the life-cycle production (including storage and field application) remains poorly elucidated. Thus, we conducted a greenhouse experiment to investigate the effects of substituting organic manure species, i.e., stored swine manure fertilizer (SS), swine manure covered by straw (CS), stored swine fertilizer mixed with biochar (BS), and stored swine manure fertilizer with void expansion (OS) for compound fertilizer (FC) on rapeseed yield and NH₃ and N₂O emissions in a rapeseed-cropping system in China. The results showed that the total gaseous N losses (NH₃ and N₂O) were 1.6, 1.4 and 1.1 times higher in SS, CS and OS than FC, respectively. However, total gaseous N losses in BS was 0.9 times less than FC. Compared with FC, rapeseed yield and N uptake in SS and CS were decreased by 17.2-20.2% and 16.0%-28.1%, respectively, but which were increased by 7.3% and 54.1% in BS, respectively. In addition, OS decreased rapeseed yield by 17.2%, but increased N uptake by 8.5%. Therefore, the effects of substituting organic manure for compound fertilizer on rapeseed yield, N uptake, NH₃ and N₂O varied regarding different organic manure species. Adopting stored swine fertilizer mixed with biochar might be a sound management practice to reduce gaseous N losses and enhance N uptake and yield in intensive vegetable production systems.

Comparison of ammonia emissions related to nitrogen use efficiency of livestock production in Europe

The increasing global demand for food and the environmental effects of reactive nitrogen losses in the food production chain, increase the need for efficient use of nitrogen (N). Of N harvested in agricultural plant products, 80% is used to feed livestock. Because the largest atmospheric loss of reactive nitrogen from livestock production systems is ammonia (NH₃), the focus of this paper is on N lost as NH₃ during the production of animal protein. The focus of this paper is to understand the key factors explaining differences in Nitrogen Use Efficiency (NUE) of animal production among various European countries. Therefore we developed a conceptual framework to describe the NUE defined as the amount of animal-protein N per N in feed and NH₃-N losses in the production of milk, beef, pork, chicken meat and eggs in The Netherlands, Switzerland, United Kingdom, Germany, Austria and Denmark. The framework describes how manure management and animal-related parameters (feed, metabolism) relate to NH₃ emissions and NUE. The results showed that the animal product with the lowest NUE had the largest NH₃ emissions and vice versa, which agrees with the reciprocal relationship between NUE and NH₃ within the conceptual framework. Across animal products for the countries considered, about 20% of the N in feed is lost as NH₃. The significant smallest proportion (12%) of NH₃-N per unit of Nfeed is from chicken production. The proportions for other products are 17%, 19%, 20% and 22% for milk, pork, eggs and beef respectively. These differences were not significantly different due to the differences among countries. For all countries, NUE was lowest for beef and highest for chicken. The production of 1 kg N in beef required about 5 kg N in feed, of which 1 kg N was lost as NH₃-N. For the production of 1 kg N in chicken meat, 2 kg N in feed was required and 0.2 kg was lost as NH₃. The production of 1 kg N in milk required 4 kg N in feed with 0.6 kg NH₃-N loss, the same as pork and eggs, but those needed 3 and 3.5 kg N in feed per kg N in product respectively. Except for beef, the differences among these European countries were mainly caused by differences in manure management practices and their emission factors, rather than by animal-related factors including feed and digestibility influencing the excreted amount of ammoniacal N (TAN). For beef, both aspects caused important differences. Based on the results, we encourage the expression of N losses as per N in feed or per N in product, in addition to per animal place, when comparing production efficiency and NUE. We consider that disaggregating emission factors into a diet/animal effect and a manure management effect would improve the basis for comparing national NH₃ emission inventories.

A new torrefaction system employing spontaneous self-heating of livestock manure under elevated pressure

This report describes a new oxidative torrefaction method employing spontaneous self-heating of feedstock as a means of overcoming practical difficulties in converting livestock manure to biochar. We examined the initiating temperature required to induce self-heating of wet dairy cattle manure under 1.0 MPa pressure and conducted elemental and calorific analyses of the solid products prepared at 200, 250, and 300 °C. Self-heating was initiated with oxidation below 100 °C, and the lower limit of the initiation temperature was between 85 and 90 °C. Comparing processes performed at 0.1 and 1.0 MPa, the higher pressure promoted self-heating by both preventing heat loss due to moisture evaporation occurring at approximately 100 °C and supplying oxygen to the high-moisture feedstock. In addition, as drying occurred at 160-170 °C during the process, the system did not require pre- or post-drying. Although the heating values of the solid products decreased due to high ash content, the elemental composition of the products was altered to that of peat-like (200 °C) and lignite-like (250 and 300 °C) materials. Cessation of self-heating of the manure is recommended at approximately 250 °C to avoid severe decomposition at higher temperatures. Overall, these results demonstrated the utility of the proposed method for converting wet manure into dried biochar through self-heating as well as potential applications in manure management systems.

Optimizing accuracy of sampling protocols to measure nutrient content of solid manure

Precise applications of manure to cropland can help optimize productivity and minimize environmental nutrient losses. Applying manure precisely is a challenge because the nutrient content of manures is inherently variable and the accuracy of sampling protocols are unknown. This study aimed to quantify the accuracy of sampling protocols for static solid manure piles considering both the number and depth of grab samples entering a composite sample. Over 35 grab samples were collected from each of ten static piles of dairy manure in California's Central Valley. Grab samples were individually analyzed for dry matter (DM), ash, total nitrogen, potassium, and phosphorous concentrations. Resampling simulations quantified the precision and bias of sampling protocols varying in both grab sample number and depth. Results showed that number of grab samples required for measurements to meet an accuracy standard of ±10% of the true value varied significantly by pile makeup. Over 25 grab samples were often required for multi-source manure piles, where an average of six grab samples were required from single source piles. The DM concentration of manure piles decreased at depths greater than 0.4 m, and sampling simulations showed that measurements were biased unless 70-80% of grab samples were collected from the pile interior. Both the number and location of grab samples necessary to create a representative composite require resource investments by farmers, and should be considered to manage nutrient applications cropland.

Potential for mitigating global agricultural ammonia emission: A meta-analysis

Ammonia (NH₃) emission from agricultural sources has contributed significantly to air pollution, soil acidification, water eutrophication, biodiversity loss, and declining human health. Although there are numerous strategies for reducing NH₃ emission from agricultural systems, the effectiveness of these measures is highly variable. Furthermore, the integrated assessment of measures to reduce NH₃ emission both from livestock production and cropping systems based on animal and crop type is lacking. Therefore, we conducted a global meta-analysis and integrated assessment of measures to reduce NH₃ emission from agricultural systems. Most of the studied mitigation strategies were effective in reducing NH₃ emission. In the livestock production system, dietary additive, urease inhibitor (UI), manure acidification and deep manure placement have the highest mitigation potential relative to other mitigation strategies, with reduction ranges of 35.1-54.2%, 24.3-68.7%, 88.8-95.0%, and 93.8-99.7%, respectively, relative to the control, while manure storage management could significantly reduce NH₃ emission by 70.0-82.1%. In the cropping system, fertilizer source, use of enhanced efficiency fertilizers, and method of field application are most effective for reducingNH₃ emission. The use of ammonium nitrate, controlled release fertilizer (CRF), and deep placement of fertilizers could reduce NH₃ emission by 88.3, 56.8, and 48.0%, respectively. Choosing a proper fertilizer is critical for decreasing NH₃ emission from cropping systems. We conclude that carefully planned and adopted strategies suited for local conditions are promising for minimizing NH₃ emission from agricultural systems on a global scale, while possible effects of those mitigation measures on the emission of greenhouse gases should be studied in the future.

Nutrient use efficiencies, losses, and abatement strategies for peri-urban dairy production systems

Manure management is an important aspect of urban livestock production that has a profound impact on metropolitan living. Data were collected from 28 dairy farms in peri-urban Beijing and analysed to determine farm nitrogen and phosphorus flows and costs associated with various manure management options to reduce nutrient losses. Dairy production in peri-urban Beijing was characterized by its use of high protein diets (16.3-17.0% crude protein), high reliance on imported feeds (92-98%), and low manure recycling (3.0-10.8%). Farms of 900-2000 cattle showed lower use efficiencies than farms of <900 cattle. Costs of manure handling ranged from 0.1 to 1.0 Yuan kg^-1 milk. Among various manure treatment options, biogas digesters with aerobic lagoons had the lowest N losses and costs, justifying their investments. In conclusion, peri-urban dairy production systems were contrasting with traditional systems and within their own systems in nutrient use efficiency and losses, which was mainly decided by their farm size. To improve the nutrient use efficiencies and reduce losses, farmers and managers of peri-urban dairy production system should have a full awareness of different feed intake and manure management.

Environmental impacts and resource use of milk production on the North China Plain, based on life cycle assessment

Life cycle assessment methodology was used to quantify the environmental impacts and resource use of milk production on the North China Plain, the largest milk production area in China. Variation in environmental burden caused by cow productivity was evaluated, as well as scenario analysis of the effects of improvement practices. The results indicated that the average environmental impact potential and resource use for producing 1kg of fat and protein corrected milk was 1.34kgCO₂eq., 9.27gPO₄^3-eq., 19.5gSO₂eq., 4.91MJ, 1.83m² and 266L for global warming potential (GWP), eutrophication potential (EP), acidification potential (AP), non-renewable energy use (NREU), land use (LU) and blue water use (BWU; i.e. water withdrawal), respectively. Feed production was a significant determinant of GWP, NREU, LU and BWU, while AP and EP were mainly affected by manure management. Scenario analysis showed that reducing use of concentrates and substituting with alfalfa hay decreased GWP, EP, AP, NREU and LU (by 1.0%-5.5%), but caused a significant increase of BWU (by 17.2%). Using imported soybean instead of locally-grown soybean decreased LU by 2.6%, but significantly increased GWP and NREU by 20% and 6.9%, respectively. There was no single perfect manure management system, with variable effects from different management practices. The environmental burden shifting observed in this study illustrates the importance of assessing a wide range of impact categories instead of single or limited indicators for formulating environmental policies, and the necessity of combining multiple measures to decrease the environmental burden. For the North China Plain, improving milking cow productivity and herd structure (i.e. increased proportion of milking cows), combining various manure management systems, and encouraging dairy farmers to return manure to nearby crop lands are promising measures to decrease multiple environmental impacts.

On the systematic underestimation of methane conversion factors in IPCC guidance

This paper documents a systematic underestimation in how the Tier 2 methane conversion factors (MCF) are calculated in IPCC (2006) guidelines for liquid manure management. The first issue is the use of annual average temperature as an input to a non-linear function describing methane production. As expected based on Jensen's inequality, the MCF calculated based on annual average temperature is always an underestimate. In regions with large intra-annual temperature ranges, such as temperate climates, the underestimation can exceed 30%. A second issue is the lack of consideration for volatile solids retention time. Future updates to the IPCC methodology should therefore account for intra-annual temperature regime and retention time-not simply annual average temperature.

Environmental status of livestock and poultry sectors in China under current transformation stage

Intensive animal husbandry had aroused great environmental concerns in many developed countries. However, some developing countries are still undergoing the environmental pollution from livestock and poultry sectors. Driven by the large demand, China has experienced a remarkable increase in dairy and meat production, especially in the transformation stage from conventional household breeding to large-scale industrial breeding. At the same time, a large amount of manure from the livestock and poultry sector is released into waterbodies and soil, causing eutrophication and soil degradation. This condition will be reinforced in the large-scale cultivation where the amount of manure exceeds the soil nutrient capacity, if not treated or utilized properly. Our research aims to analyze whether the transformation of raising scale would be beneficial to the environment as well as present the latest status of livestock and poultry sectors in China. The estimation of the pollutants generated and discharged from livestock and poultry sector in China will facilitate the legislation of manure management. This paper analyzes the pollutants generated from the manure of the five principal commercial animals in different farming practices. The results show that the fattening pigs contribute almost half of the pollutants released from manure. Moreover, the beef cattle exert the largest environmental impact for unitary production, about 2-3 times of pork and 5-20 times of chicken. The animals raised with large-scale feedlots practice generate fewer pollutants than those raised in households. The shift towards industrial production of livestock and poultry is easier to manage from the environmental perspective, but adequate large-scale cultivation is encouraged. Regulation control, manure treatment and financial subsidies for the manure treatment and utilization are recommended to achieve the ecological agriculture in China.

Manure management and public health: Sanitary and socio-economic aspects among urban livestock-keepers in Cambodia

Livestock manure is a valuable source of nutrients for crop production, but can also pose a public health hazard and have negative environmental impacts. This study investigated manure management practices among urban and peri-urban livestock keepers in Cambodia, to identify risk behaviours and socio-economic aspects associated with the handling of manure. A survey including 204 households was conducted, using a structured questionnaire with questions on demographics, socio-economic characteristics and household practices related to manure management. Faecal samples were obtained from pig pens and pig manure storage units for analysis of the potential zoonotic pathogens Salmonella enterica (Polymerase Chain Reaction (PCR)), Ascaris suum and Trichuris suis (McMaster flotation technique). The survey revealed a difference in management between cattle and pig manure. Cattle manure was most commonly used as fertiliser for crop production (66%) (p<0.001), whereas pig manure was most commonly dumped in the environment (46%) (p<0.001). Logistic regression models showed that households with a lower socio-economic position were more likely to dump pig manure (p<0.001), with scarcity of agricultural land (p<0.001) and lack of carts for transportation of manure (p<0.01) being identified as contributing factors. Salmonella enterica was detected in 9.7% of manure samples, while Ascaris suum and Trichuris suis were detected in 1.6% and 2.4% of the samples, respectively. The results presented in this study indicate that manure management by urban and peri-urban households may pose a public health threat and an environmental hazard. There is evidently a need for further knowledge support to the livestock keepers to promote good management practices.

Larval digestion of different manure types by the black soldier fly (Diptera: Stratiomyidae) impacts associated volatile emissions

Volatile emissions from decomposing animal waste are known environmental pollutants. The black soldier fly, Hermetia illucens (L.), is being evaluated for industrialization as a means to recycle wastes and produce protein for use as food and feed. We examined the ability of black soldier fly larvae to reduce odorous compounds associated with animal wastes. Black soldier fly larvae were reared under laboratory conditions on poultry, swine, and dairy manure at feed rates of 18.0 and 27.0 g every other day until 40% reached the prepupal stage. Volatile emissions were collected and analyzed from freshly thawed as well as the digested waste when 90% of the black soldier fly larvae reached the prepupal stage. Volatiles were also collected simultaneously from manure not inoculated with black soldier fly larvae (non-digested) and held under similar conditions. Manure samples were analyzed for relative amounts of nine select odorous volatile organic compounds: phenol, 4-methylphenol, indole, 3-methylindole, propanoic acid, 2-methylpropanoic acid, butanoic acid, 3-methylbutanoic acid and pentanoic acid. Black soldier fly larvae reduced emissions of all volatile organic compounds by 87% or greater. Complete reductions were observed for 2-methly propanoic acid in digested poultry manure, phenol, 4-methylphenol, indole and all five fatty acids in digested swine manure, and 4-methylphenol, indole, 3-methylindole and all five acids in digested dairy manure. This study is the first to identify volatile emissions from manure digested by black soldier fly larvae and compare to those found in non-digested manure. These data demonstrate additional benefits of using black soldier fly larvae as a cost-effective and environmentally friendly means of livestock manure management in comparison to current methods.

CAPSULE

Black soldier fly larvae are capable of altering the overall profile of volatile organic compounds and reducing levels of targeted odorous compounds in livestock manure.

The carbon footprint of integrated milk production and renewable energy systems - A case study

Dairy farms have been widely acknowledged as a source of greenhouse gas (GHG) emissions. The need for a more environmentally friendly milk production system will likely be important going forward. Whereas methane (CH₄) enteric emissions can only be reduced to a limited extent, CH₄ manure emissions can be reduced by implementing mitigation strategies, such as the use of an anaerobic digestion (AD). Furthermore, implementing a photovoltaic (PV) electricity generation system could mitigate the fossil fuels used to cover the electrical needs of farms. In the present study to detect the main environmental hotspots of milk production, a Life Cycle Assessment was adopted to build the Life Cycle Inventory according to ISO 14040 and 14044 in a conventional dairy farm (1368 animals) provided by AD and PV systems. The Intergovernmental Panel on Climate Change tiered approach was adopted to associate the level of emission with each item in the life cycle inventory. The functional unit refers to 1kg of fat-and-protein-corrected-milk (FPCM). In addition to milk products, other important co-products need to be considered: meat and renewable energy production from AD and PV systems. A physical allocation was applied to attribute GHG emissions among milk and meat products. Renewable energy production from AD and PV systems was considered, discounting carbon credits due to lower CH₄ manure emissions and to the minor exploitation of fossil energy. The CF of this farm scenario was 1.11kg CO₂eq/kg FPCM. The inclusion of AD allowed for the reduction of GHG emissions from milk production by 0.26kg CO₂eq/kg FPCM. The PV system contribution was negligible due to the small dimensions of the technology. The results obtained in this study confirm that integrating milk production with other co-products, originated from more efficient manure management, is a successful strategy to mitigate the environmental impact of dairy production.

Greenhouse gas and ammonia emissions from production of compost bedding on a dairy farm

Recent developments in composting technology enable dairy farms to produce their own bedding from composted manure. This management practice alters the fate of carbon and nitrogen; however, there is little data available documenting how gaseous emissions are impacted. This study measured in-situ emissions of methane (CH₄), carbon dioxide (CO₂), nitrous oxide (N₂O), and ammonia (NH₃) from an on-farm solid-liquid separation system followed by continuously-turned plug-flow composting over three seasons. Emissions were measured separately from the continuously-turned compost phase, and the compost-storage phase prior to the compost being used for cattle bedding. Active composting had low emissions of N₂O and CH₄ with most carbon being emitted as CO₂-C and most N emitted as NH₃-N. Compost storage had higher CH₄ and N₂O emissions than the active phase, while NH₃ was emitted at a lower rate, and CO₂ was similar. Overall, combining both the active composting and storage phases, the mean total emissions were 3.9×10^-2gCH₄kg^-1 raw manure (RM), 11.3gCO₂kg^-1 RM, 2.5×10^-4g N₂O kg^-1 RM, and 0.13g NH₃ kg^-1 RM. Emissions with solid-separation and composting were compared to calculated emissions for a traditional (unseparated) liquid manure storage tank. The total greenhouse gas emissions (CH₄+N₂O) from solid separation, composting, compost storage, and separated liquid storage were reduced substantially on a CO₂-equivalent basis compared to traditional liquid storage. Solid-liquid separation and well-managed composting could mitigate overall greenhouse gas emissions; however, an environmental trade off was that NH₃ was emitted at higher rates from the continuously turned composter than reported values for traditional storage.

Nutrient losses and greenhouse gas emissions from dairy production in China: Lessons learned from historical changes and regional differences

The dairy industry in China was rapidly expanded and intensified from 1980 to 2010, engendering potential long-term impacts on the environment and natural resources. However, impacts of dairy intensification on nitrogen (N) and phosphorus (P) losses and greenhouse gas (GHG) emissions were unknown. This study was undertaken to examine these relations using the NUtrient flows in Food chains, Environment and Resources use (NUFER)-dairy model. Results showed that milk yield increased by 64% from 1980 to 2010 on average, and the use of concentrate feeds increased by 57% associated with a shift of production from traditional and grassland systems to collective and industrialized systems. At herd level, the N use efficiency (NUE; conversion of N inputs to products) doubled from 7 to 15%, and the P use efficiency (PUE) increased from 10 to 17%, primarily resulting from increased milk yield per cow. In contrast, at the system level, NUE showed a small increase (from 10 to 15%, associated with reduced gaseous losses) while PUE decreased from 46 to 30% due to a large increase in manure discharges. This is attributed to decoupling of feed and dairy production, as the proportion of manure N and P recycled to cropland decreased by 52% and 54%, respectively. Despite this, the average total N loss decreased from 63 to 48gkg^-1 milk, and the average GHG emissions from 1.7 to 1.1kgCO₂equivalentkg^-1 milk associated with increased per-cow productivity. However, average P loss increased from 1.4 to 2.8gPkg^-1 milk due to higher discharge rate to wastewater and landfill in collective and industrialized systems. Anyhow, average N and P losses exceeded levels in developed countries. There were large regional variations in nutrient use efficiency, nutrient losses and GHG emissions in China, largely determined by the dairy production structure. Average N losses and GHG emissions per unit of milk showed a negative correlation with production intensification based on the proportion of farms in collective or industrialized systems, while average P losses per unit of milk in different regions showed a positive relationship with intensification. In conclusion, dairy intensification was associated with increased milk yield per cow and reduced average N losses and GHG emissions per unit of milk, but reduced system level PUE and manure recycling contributed to high levels of total N and P losses. Dairy production in China is likely to continue to be intensified as a result of rising milk demand, and significant improvements must be made in manure management to control N and P losses and GHG emissions.

Nitrogen removal from digested slurries using a simplified ammonia stripping technique

This study assessed a novel technique for removing nitrogen from digested organic waste based on a slow release of ammonia that was promoted by continuous mixing of the digestate and delivering a continuous air stream across the surface of the liquid. Three 10-day experiments were conducted using two 50-L reactors. In the first two, nitrogen removal efficiencies were evaluated from identical digestates maintained at different temperatures (30°C and 40°C). At the start of the first experiment, the digestates were adjusted to pH 9 using sodium hydroxide, while in the second experiment pH was not adjusted. The highest ammonia removal efficiency (87%) was obtained at 40°C with pH adjustment. However at 40°C without pH adjustment, removal efficiencies of 69% for ammonia and 47% for total nitrogen were obtained. In the third experiment two different digestates were tested at 50°C without pH adjustment. Although the initial chemical characteristics of the digestates were different in this experiment, the ammonia removal efficiencies were very similar (approximately 85%). Despite ammonia removal, the pH increased in all experiments, most likely due to carbon dioxide stripping that was promoted by temperature and mixing. The technique proved to be suitable for removing nitrogen following anaerobic digestion of livestock manure because effective removal was obtained at natural pH (≈8) and 40°C, common operating conditions at typical biogas plants that process manure. Furthermore, the electrical energy requirement to operate the process is limited (estimated to be 3.8kWhm^-3digestate). Further improvements may increase the efficiency and reduce the processing time of this treatment technique. Even without these advances slow-rate air stripping of ammonia is a viable option for reducing the environmental impact associated with animal manure management.

Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock

BACKGROUND

Livestock play an important role in carbon cycling through consumption of biomass and emissions of methane. Recent research suggests that existing bottom-up inventories of livestock methane emissions in the US, such as those made using 2006 IPCC Tier 1 livestock emissions factors, are too low. This may be due to outdated information used to develop these emissions factors. In this study, we update information for cattle and swine by region, based on reported recent changes in animal body mass, feed quality and quantity, milk productivity, and management of animals and manure. We then use this updated information to calculate new livestock methane emissions factors for enteric fermentation in cattle, and for manure management in cattle and swine.

RESULTS

Using the new emissions factors, we estimate global livestock emissions of 119.1 ± 18.2 Tg methane in 2011; this quantity is 11% greater than that obtained using the IPCC 2006 emissions factors, encompassing an 8.4% increase in enteric fermentation methane, a 36.7% increase in manure management methane, and notable variability among regions and sources. For example, revised manure management methane emissions for 2011 in the US increased by 71.8%. For years through 2013, we present (a) annual livestock methane emissions, (b) complete annual livestock carbon budgets, including carbon dioxide emissions, and (c) spatial distributions of livestock methane and other carbon fluxes, downscaled to 0.05 × 0.05 degree resolution.

CONCLUSIONS

Our revised bottom-up estimates of global livestock methane emissions are comparable to recently reported top-down global estimates for recent years, and account for a significant part of the increase in annual methane emissions since 2007. Our results suggest that livestock methane emissions, while not the dominant overall source of global methane emissions, may be a major contributor to the observed annual emissions increases over the 2000s to 2010s. Differences at regional and local scales may help distinguish livestock methane emissions from those of other sectors in future top-down studies. The revised estimates allow improved reconciliation of top-down and bottom-up estimates of methane emissions, will facilitate the development and evaluation of Earth system models, and provide consistent regional and global Tier 1 estimates for environmental assessments.