Modeling the environmental impacts of Asparagopsis as feed, a cow toilet and slurry acidification in two synthetic dairy farms.

Intensive dairy farming, particularly enteric fermentation and manure management, is a major contributor to negative impacts on the local and global environment. A wide range of abatement measures has been proposed to reduce livestock-related emissions, yet the individual and combined effects of these innovations are often unknown. In this study, we performed an attributional life cycle assessment of three innovative measures modeled in two synthetic German dairy farm systems: Feeding of the seaweed Asparagopsis, installing an in-house cow toilet system, and performing on-field slurry acidification. These measures were modeled both individually and in combination to account for single and cumulative effects and compared to a reference scenario under current practices. Our results showed that feeding high levels of Asparagopsis and the combination of all three measures were most effective at reducing global warming potential (20-30 %), while only the latter mitigated eutrophication (6-9%) and acidification potential (14-17 %). The cow toilet required additional adapted manure management (separated storage and injection of urine) to effectively reduce eutrophication (8-10 %) and acidification potential (19-23 %) and to decrease global warming potential (3-4%) and abiotic depletion (4-5%). Slurry acidification slightly affected all considered environmental impact categories. All three measures involved trade-offs, either between LCA impact categories (global warming potential vs. abiotic depletion), the location of impacts (off- vs. on-farm), or the emission reduction in individual gases (ammonia vs. nitrous oxide). Measure combinations could compensate for the observed trade-offs. Our study highlights the potential of novel abatement measures but also shows the interdependencies of measures in different stages. This calls for a revisiting of current priorities in funding and legislation, which often focus on single objectives and measures (e.g. ammonia reduction) toward the preferential use of measures that are effective without driving trade-offs or improving resource efficiency.

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.

Effects of environmental and housing system factors on ammonia and greenhouse gas emissions from cattle barns: A meta-analysis of a global data collation.

This study provides a meta-analysis on the relationships between cattle barn CH4, NH3 and N2O emission rates and their key drivers (i.e., housing type, floor type, environmental conditions). Understanding these relationships is essential to reduce uncertainties in emission inventories and suggest targeted mitigation measures. The total number of daily emission rates included in the analysis was 139 for CH4, 293 for NH3 and 100 for N2O emissions. Emission rates in the database showed a large variation with 45-803.5 g/LU d-1 for CH4, 0.036-146.7 gN LU-1 d-1 for NH3, and 0.002-18 gN LU-1 d-1 for N2O emissions. Despite the high emission variability, significant effects were identified·NH3 showed positive correlation with air temperature; NH3 emissions differed between housing types but not between floor types·NH3 emissions from tied stalls were lower than the ones from cubicle housing regardless of the floor type. Additionally, NH3 emissions from loose housings were lower than the ones from cubicle housing·NH3 and N2O emission rates from temperate wet zones were lower than the ones from temperate dry zones. CH4 emission rates were affected by environmental factors only and not by housing and floor type, showing negative correlation with air temperature and humidity. The factors investigated can be suggested as ancillary variables and descriptors when cattle barn emissions are measured, in order to make best use of emission data. Country-specific data of these key drivers can be included into national inventories to adapt them to different agroecosystems and support targeted policies.

Costs and effects of measures to reduce ammonia emissions from dairy cattle and pig production: A comparison of country-specific estimations and model calculations.

Understanding the costs of emission abatement measures is essential for devising reduction efforts. It allows to identify cost-effective solutions to achieve target values set by international agreements or national policies. This work aims to summarize and discuss the current knowledge on costs and effects associated with selected ammonia (NH3) mitigation measures in livestock production through comparison of country-specific and model-estimated values. Often, large differences appear between the results of individual countries, also in comparison with model results that are generally better harmonized between countries. It seems that different system boundaries in cost assessments, but also different geographic and structural conditions create perceived as well as real cost differences, also caused by the variability of individual situations. Our results are robust with respect to identifying feeding strategies as the most cost-effective, but results for other mitigation options do not show any clear trends, thus making it difficult to distinguish further cost-effective solutions. We point out and discuss some key aspects which may affect estimates of national costs, leading to challenges with the interpretation of final results. Our study concludes that further and more consistent assessments (e.g. standardized protocols) are needed to improve the evaluation base for other individual abatement options, including options that are under development.

Assessment of the biochemical methane potential of in-house and outdoor stored pig and dairy cow manure by evaluating chemical composition and storage conditions.

Biogas production is a suitable option for producing energy from dairy and pig manure types. During manure storage, organic matter degradation results in methane emissions decreasing the potential biogas yield. The present research advances the understanding of the biochemical methane potential (BMP) and the chemical characteristics of manure collected year-round from sequential stages of the liquid manure management chain of commercial dairy cow and pig farms. To this end, manure samples from six livestock farms in Germany were analyzed. The results showed that changes in chemical composition during storage led to a 20.5% decrease in the BMP of dairy manure from the barn to outdoor storage. For fattening pig manure samples, there was a 39.5% decrease in the BMP from intermediate to outdoor storage. An analysis of BMP according to manure age showed that pig manure degrades faster than dairy manure; the importance of promptly feeding manure to the biogas plant in order to avoid significant CH4 emission losses and reduction in energy producing capacity was highlighted. The best BMP predictors for dairy manure were the contents of dry matter, volatile solids and lignin, whereas best BMP predictors for pig manure were dry matter and volatile fatty acid (VFA) content. Prediction models performed well for samples from outdoor storages; refinements for predicting BMP of less aged samples presenting lower chemical variability would be necessary.

DATAMAN: A global database of methane, nitrous oxide, and ammonia emission factors for livestock housing and outdoor storage of manure.

Livestock manure management systems can be significant sources of nitrous oxide (N2 O), methane (CH4 ), and ammonia (NH3 ) emissions. Many studies have been conducted to improve our understanding of the emission processes and to identify influential variables in order to develop mitigation techniques adapted to each manure management step (animal housing, outdoor storage, and manure spreading to land). The international project DATAMAN (http://www.dataman.co.nz) aims to develop a global database on greenhouse gases (N2 O, CH4 ) and NH3 emissions from the manure management chain to refine emission factors (EFs) for national greenhouse gas and NH3 inventories. This paper describes the housing and outdoor storage components of this database. Relevant information for different animal categories, manure types, livestock buildings, outdoor storage, and climatic conditions was collated from published peer reviewed research, conference papers, and existing databases published between 1995 and 2021. In the housing database, 2024 EFs were collated (63% for NH3 , 19.5% for CH4 , and 17.5% for N2 O). The storage database contains 654 NH3 EFs from 16 countries, 243 CH4 EFs from 13 countries, and 421 N2 O EFs from 17 countries. Across all gases, dairy cattle and swine production in temperate climate zones are the most represented animal and climate categories. As for the housing database, the number of EFs for the tropical climate zone is under-represented. The DATAMAN database can be used for the refinement of national inventories and better assessment of the cost-effectiveness of a range of mitigation strategies.

Comparison of nitrogen losses from different manure treatment and application management systems in China.

There is a worldwide focus on reducing the environmental impacts of livestock manure management. In China, there are different manure treatment and application modes, including complete treatment to remove nitrogen (N) for direct discharge into watercourses. But we lack a systematic quantitative comparison of the environmental losses that occur from different management modes. We used an example farm of 10,000 finisher pigs to quantitatively analyze the annual N losses from land application (LA) and treatment to remove N from manure to the level of discharge consent (DS) under 24 sub-modes. This is an important study to unravel the effect of choice of different manure management systems on subsequent N losses. The results showed that the N losses from the LA mode (52.6% of total N excretion) were significantly lower than that from the DS mode (75.9%). Compared with other sub-modes, N emission from whole slurry injection was the smallest, accounting for 43.2% of total N excretion. NH3-N was the main source of N loss which accounted for 72.9% and 50.2% in LA and DS mode, respectively. The lowest N emission of LA mode with mitigation options, including slurry store covers, composting with bio-filter deodorization and injection application, was 28.8% of total N excretion, which is only 42.2% of N emission from DS mode with mitigation options. Insights from this systematic study of different manure management modes in China show the imperative of control ammonia emission for China, and provide guidance to the sustainable manure management in rapidly developing countries.

Ammonia and nitrous oxide emission factors for excreta deposited by livestock and land-applied manure.

Manure application to land and deposition of urine and dung by grazing animals are major sources of ammonia (NH3 ) and nitrous oxide (N2 O) emissions. Using data on NH3 and N2 O emissions following land-applied manures and excreta deposited during grazing, emission factors (EFs) disaggregated by climate zone were developed, and the effects of mitigation strategies were evaluated. The NH3 data represent emissions from cattle and swine manures in temperate wet climates, and the N2 O data include cattle, sheep, and swine manure emissions in temperate wet/dry and tropical wet/dry climates. The NH3 EFs for broadcast cattle solid manure and slurry were 0.03 and 0.24 kg NH3 -N kg-1 total N (TN), respectively, whereas the NH3 EF of broadcast swine slurry was 0.29. Emissions from both cattle and swine slurry were reduced between 46 and 62% with low-emissions application methods. Land application of cattle and swine manure in wet climates had EFs of 0.005 and 0.011 kg N2 O-N kg-1 TN, respectively, whereas in dry climates the EF for cattle manure was 0.0031. The N2 O EFs for cattle urine and dung in wet climates were 0.0095 and 0.002 kg N2 O-N kg-1 TN, respectively, which were three times greater than for dry climates. The N2 O EFs for sheep urine and dung in wet climates were 0.0043 and 0.0005, respectively. The use of nitrification inhibitors reduced emissions in swine manure, cattle urine/dung, and sheep urine by 45-63%. These enhanced EFs can improve national inventories; however, more data from poorly represented regions (e.g., Asia, Africa, South America) are needed.

Particulate matter emissions during field application of poultry manure - The influence of moisture content and treatment.

Along with industry and transportation, agriculture is one of the main sources of primary particulate matter (PM) emissions worldwide. Bioaerosol formation and PM release during livestock manure field application and the associated threats to environmental and human health are rarely investigated. In the temperate climate zone, field fertilization with manure seasonally contributes to local PM air pollution regularly twice per year (spring and autumn). Measurements in a wind tunnel, in the field and computational fluid dynamics (CFD) simulations were performed to analyze PM aerosolization during poultry manure application and the influence of manure moisture content and treatment. A positive correlation between manure dry matter content (DM) and PM release was observed. Therefore, treatments strongly increasing the DM of poultry manure should be avoided. However, high manure DM led to reduced microbial abundance and, therefore, to a lower risk of environmental pathogen dispersion. Considering the findings of PM and microbial measurements, the optimal poultry manure DM range for field fertilization was identified as 50-70%. Maximum PM10 concentrations of approx. 10 mg per m3 of air were measured during the spreading of dried manure (DM 80%), a concentration that is classified as strongly harmful. The modeling of PM aerosolization processes indicated a low health risk beyond a distance of 400 m from the manure application source. The detailed knowledge about PM aerosolization during manure field application was improved with this study, enabling manure management optimization for lower PM aerosolization and pathogenic release into the environment.

Methane emissions from the storage of liquid dairy manure: Influences of season, temperature and storage duration.

Methane emissions from livestock manure are primary contributors to GHG emissions from agriculture and options for their mitigation must be found. This paper presents the results of a study on methane emissions from stored liquid dairy cow manure during summer and winter storage periods. Manure from the summer and winter season was stored under controlled conditions in barrels at ambient temperature to simulate manure storage conditions. Methane emissions from the manure samples from the winter season were measured in two time periods: 0 to 69 and 0 to 139 days. For the summer storage period, the experiments covered four time periods: from 0 to 70, 0 to 138, 0 to 209, and 0 to 279 continuous days, with probing every 10 weeks. Additionally, at the end of all storage experiments, samples were placed into eudiometer batch digesters, and their methane emissions were measured at 20 °C for another 60 days to investigate the potential effect of the aging of the liquid manure on its methane emissions. The experiment showed that the methane emissions from manure stored in summer were considerably higher than those from manure stored in winter. CH4 production started after approximately one month, reaching values of 0.061 kg CH4 kg-1 Volatile Solid (VS) and achieving high total emissions of 0.148 kg CH4 kg-1 VS (40 weeks). In winter, the highest emissions level was 0.0011 kg CH4 kg-1 VS (20 weeks). The outcomes of these experimental measurements can be used to suggest strategies for mitigating methane emissions from manure storage.

DATAMAN: A global database of nitrous oxide and ammonia emission factors for excreta deposited by livestock and land-applied manure.

Nitrous oxide (N2 O), ammonia (NH3 ), and methane (CH4 ) emissions from the manure management chain of livestock production systems are important contributors to greenhouse gases (GHGs) and NH3 emitted by human activities. Several studies have evaluated manure-related emissions and associated key variables at regional, national, or continental scales. However, there have been few studies focusing on the drivers of these emissions using a global dataset. An international project was created (DATAMAN) to develop a global database on GHG and NH3 emissions from the manure management chain (housing, storage, and field) to identify key variables influencing emissions and ultimately to refine emission factors (EFs) for future national GHG inventories and NH3 emission reporting. This paper describes the "field" database that focuses on N2 O and NH3 EFs from land-applied manure and excreta deposited by grazing livestock. We collated relevant information (EFs, manure characteristics, soil properties, and climatic conditions) from published peer-reviewed research, conference papers, and existing databases. The database, containing 5,632 observations compiled from 184 studies, was relatively evenly split between N2 O and NH3 (56 and 44% of the EF values, respectively). The N2 O data were derived from studies conducted in 21 countries on five continents, with New Zealand, the United Kingdom, Kenya, and Brazil representing 86% of the data. The NH3 data originated from studies conducted in 17 countries on four continents, with the United Kingdom, Denmark, Canada, and The Netherlands representing 79% of the data. Wet temperate climates represented 90% of the total database. The DATAMAN field database is available at http://www.dataman.co.nz.

Direct Measurements of the Volume Flow Rate and Emissions in a Large Naturally Ventilated Building.

The direct measurement of emissions from naturally ventilated dairy barns is challenging due to their large openings and the turbulent and unsteady airflow at the inlets and outlets. The aim of this study was to quantify the impacts of the number and positions of sensors on the estimation of volume flow rate and emissions. High resolution measurements of a naturally ventilated scaled building model in an atmospheric boundary layer wind tunnel were done. Tracer gas was released inside the model and measured at the outlet area, using a fast flame ionization detector (FFID). Additionally, the normal velocity on the area was measured using laser Doppler anemometry (LDA). In total, for a matrix of 65 × 4 sensor positions, the mean normal velocities and the mean concentrations were measured and used to calculate the volume flow rate and the emissions. This dataset was used as a reference to assess the accuracy while systematically reducing the number of sensors and varying the positions of them. The results showed systematic errors in the emission estimation up to +97%, when measurements of concentration and velocity were done at one constant height. This error could be lowered under 5%, when the concentrations were measured as a vertical composite sample.

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.

The value of manure - Manure as co-product in life cycle assessment.

Livestock production is important for food security, nutrition, and landscape maintenance, but it is associated with several environmental impacts. To assess the risk and benefits arising from livestock production, transparent and robust indicators are required, such as those offered by life cycle assessment. A central question in such approaches is how environmental burden is allocated to livestock products and to manure that is re-used for agricultural production. To incentivize sustainable use of manure, it should be considered as a co-product as long as it is not disposed of, or wasted, or applied in excess of crop nutrient needs, in which case it should be treated as a waste. This paper proposes a theoretical approach to define nutrient requirements based on nutrient response curves to economic and physical optima and a pragmatic approach based on crop nutrient yield adjusted for nutrient losses to atmosphere and water. Allocation of environmental burden to manure and other livestock products is then based on the nutrient value from manure for crop production using the price of fertilizer nutrients. We illustrate and discuss the proposed method with two case studies.

Effects of the daily heat load duration exceeding determined heat load thresholds on activity traits of lactating dairy cows.

In recent years, the problem of the welfare and heat load of dairy cows has become increasingly important in moderate climate zones. The objective of the present study was to determine heat load thresholds of average daily temperature-humidity index (THI) that lead to changes in different activity traits of lactating high-yielding dairy cows. Furthermore, we studied how the activity of the cows to heat load was influenced by the daily heat load duration which exceeded the heat load we had determined as threshold in our experiments. The study was conducted from June 2015 to May 2017 in a naturally ventilated dairy barn in Groß Kreutz, Germany. The climate was measured at several positions inside the barn, and the average THI was calculated every 10 min. The THI was used to define the dairy cows' heat load exposure. In addition, the activity of the cows was measured by pedometers, and different activity traits were recorded in the functional groups "resting behavior" and "locomotion behavior". The heat load thresholds determined by broken-stick models were 47 THI (standing bout duration, number of steps) as well as 67 THI (total lying/standing time, number of lying/standing bouts, lying bout duration). During the experimental period, the most reliable heat load threshold of 67 THI was exceeded from May to September for up to 480 h per month. The analysis model of each activity trait included the effect of the average daily THI values below and above the determined heat load threshold and the effect of the daily heat load duration exceeding the determined heat load threshold. The total lying/standing time and the number of steps showed significant changes related to increasing daily heat load duration. The effect of the daily heat load duration additionally intensified the effect of the average daily THI.

Greenhouse Gas and Ammonia Emissions from Different Stages of Liquid Manure Management Chains: Abatement Options and Emission Interactions.

Farm livestock manure is an important source of ammonia and greenhouse gases. Concerns over the environmental impact of emissions from manure management have resulted in research efforts focusing on emission abatement. However, questions regarding the successful abatement of manure-related emissions remain. This study uses a meta-analytical approach comprising 89 peer-reviewed studies to quantify emission reduction potentials of abatement options for liquid manure management chains from cattle and pigs. Analyses of emission reductions highlight the importance of accounting for interactions between emissions. Only three out of the eight abatement options considered (frequent removal of manure, anaerobic digesters, and manure acidification) reduced ammonia (3-60%), nitrous oxide (21-55%), and methane (29-74%) emissions simultaneously, whereas in all other cases, tradeoffs were identified. The results demonstrate that a shift from single-stage emission abatement options towards a whole-chain perspective is vital in reducing overall emissions along the manure management chain. The study also identifies some key elements like proper clustering, reporting of influencing factors, and explicitly describing assumptions associated with abatement options that can reduce variability in emission reduction estimates. Prioritization of abatement options according to their functioning can help to determine low-risk emission reduction options, specifically options that alter manure characteristics (e.g., reduced protein diets, anaerobic digestion, or slurry acidification). These insights supported by comprehensive emission measurement studies can help improve the effectiveness of emission abatement and harmonize strategies aimed at reducing air pollution and climate change simultaneously.

Challenges and priorities for modelling livestock health and pathogens in the context of climate change.

Climate change has the potential to impair livestock health, with consequences for animal welfare, productivity, greenhouse gas emissions, and human livelihoods and health. Modelling has an important role in assessing the impacts of climate change on livestock systems and the efficacy of potential adaptation strategies, to support decision making for more efficient, resilient and sustainable production. However, a coherent set of challenges and research priorities for modelling livestock health and pathogens under climate change has not previously been available. To identify such challenges and priorities, researchers from across Europe were engaged in a horizon-scanning study, involving workshop and questionnaire based exercises and focussed literature reviews. Eighteen key challenges were identified and grouped into six categories based on subject-specific and capacity building requirements. Across a number of challenges, the need for inventories relating model types to different applications (e.g. the pathogen species, region, scale of focus and purpose to which they can be applied) was identified, in order to identify gaps in capability in relation to the impacts of climate change on animal health. The need for collaboration and learning across disciplines was highlighted in several challenges, e.g. to better understand and model complex ecological interactions between pathogens, vectors, wildlife hosts and livestock in the context of climate change. Collaboration between socio-economic and biophysical disciplines was seen as important for better engagement with stakeholders and for improved modelling of the costs and benefits of poor livestock health. The need for more comprehensive validation of empirical relationships, for harmonising terminology and measurements, and for building capacity for under-researched nations, systems and health problems indicated the importance of joined up approaches across nations. The challenges and priorities identified can help focus the development of modelling capacity and future research structures in this vital field. Well-funded networks capable of managing the long-term development of shared resources are required in order to create a cohesive modelling community equipped to tackle the complex challenges of climate change.

Methane production through anaerobic digestion of various energy crops grown in sustainable crop rotations.

Biogas production is of major importance for the sustainable use of agrarian biomass as renewable energy source. Economic biogas production depends on high biogas yields. The project aimed at optimising anaerobic digestion of energy crops. The following aspects were investigated: suitability of different crop species and varieties, optimum time of harvesting, specific methane yield and methane yield per hectare. The experiments covered 7 maize, 2 winter wheat, 2 triticale varieties, 1 winter rye, and 2 sunflower varieties and 6 variants with permanent grassland. In the course of the vegetation period, biomass yield and biomass composition were measured. Anaerobic digestion was carried out in eudiometer batch digesters. The highest methane yields of 7500-10200 m(N)(3)ha(-1) were achieved from maize varieties with FAO numbers (value for the maturity of the maize) of 300 to 600 harvested at "wax ripeness". Methane yields of cereals ranged from 3200 to 4500 m(N)(3)ha(-1). Cereals should be harvested at "grain in the milk stage" to "grain in the dough stage". With sunflowers, methane yields between 2600 and 4550 m(N)(3)ha(-1) were achieved. There were distinct differences between the investigated sunflower varieties. Alpine grassland can yield 2700-3500 m(N)(3)CH(4)ha(-1). The methane energy value model (MEVM) was developed for the different energy crops. It estimates the specific methane yield from the nutrient composition of the energy crops. Energy crops for biogas production need to be grown in sustainable crop rotations. The paper outlines possibilities for optimising methane yield from versatile crop rotations that integrate the production of food, feed, raw materials and energy. These integrated crop rotations are highly efficient and can provide up to 320 million t COE which is 96% of the total energy demand of the road traffic of the EU-25 (the 25 Member States of the European Union).

Methane oxidation in slurry storage surface crusts.

Livestock manure is a significant source of atmospheric methane (CH4), especially during liquid storage. In liquid manure (slurry) storages a surface crust may form naturally, or an artificial surface crust can be established. We investigated whether there is a potential for CH4 oxidation in this environment. Surface crust materials were sampled from experimental storages with cattle slurry (with natural crust) or anaerobically digested cattle slurry (with straw layer) that had been stored with or without a wooden cover. Extracts of surface crust material were incubated with 5.6% CH4 in the headspace, and methanotrophic activity was demonstrated in all four treatments following a 4- to 10-d lag phase. Subsequent incubation of field-moist surface crust material with 350 microL L(-1) CH4 also showed CH4 oxidation, indicating a potential for CH4 removal under practical storage conditions. There was no CH4 oxidation activity during incubation of autoclaved samples. Methane oxidation rates were 0.1 to 0.5 mg kg(-1) organic matter (OM) h(-1), which is comparable with the activity in wetlands and rice paddies. Partial drying increased CH4 oxidation to 0.2 to 1.4 mg kg(-1) OM h(-1), probably as a result of improved diffusivity within the surface crust. Rewetting reversed the stimulation of methanotrophic activity in some treatments, but not in others, possibly due to a decline in CH4 production in anaerobic volumes, or to growth of methanotrophs during incubation. This study presents direct evidence for methanotrophic activity in slurry storages. Measures to ensure crust formation with or without a solid cover appear to be a cost-effective greenhouse gas mitigation option.