Effect of breed and pasture type on methane emissions from weaned lambs offered fresh forage

To investigate the extent to which enteric methane (CH(4)) emissions from growing lambs are explained by simple body weight and diet characteristics, a 2 × 2 Latin square changeover design experiment was carried out using two sheep breeds and two fresh pasture types. Weaned lambs of two contrasting breed types were used: Welsh Mountain (WM, a small, hardy hill breed) and Welsh Mule × Texel (TexX, prime lamb) (n = 8 per breed). The lambs were zero-grazed on material cut from recently reseeded perennial ryegrass and extensively managed permanent pasture. In each experimental period, individual ad libitum dry matter intake (DMI) was determined indoors following an adaptation period of 2 weeks, and CH(4) emissions were measured individually in open-circuit respiration chambers over a period of 3 days. Although total daily CH(4) emissions were lower for the WM lambs than for the TexX lambs (13·3 v. 15·7 g/day, respectively) when offered fresh forage, the yield of CH(4) per unit DMI was similar for the two breed types (16·4 v. 17·7 g CH(4)/kg DMI). Total output of CH(4) per day was higher when lambs were offered ryegrass compared with permanent pasture (16·1 v. 12·9 g/day, respectively), which was probably driven by differences in DMI (986 v. 732 g/day). Methane emissions per unit DMI (16·4 v. 17·7 g CH(4)/kg DMI) and proportion of gross energy intake excreted as CH(4) (0·052 v. 0·056 MJ/MJ) were both higher on the permanent pasture. No forage × breed type interactions were identified. The results indicate that forage type had a greater impact than breed type on CH(4) emissions from growing weaned lambs. It can be concluded that when calculating CH(4) emissions for inventory purposes, it is more important to know what forages growing lambs are consuming than to know what breeds they are

Controls on CH(4) emissions from boreal and arctic wetlands

This thesis examines the environmental controls on the biogeochemical cycling of the radiatively active trace gas CH\sb4 within boreal and arctic wetlands. Net CH\sb4 flux along peatland hydrologic gradients were examined to determine the effects of temperature and water table on CH\sb4 emissions. The level of the water table acts as a switch between CH\sb4 production and oxidation with small water level changes producing large changes in flux balance. Soil temperature determined whether CH\sb4 production potential was realized within sufficiently moist environments. A selective inhibitor technique was developed for directly measuring CH\sb4 oxidation in wetland soils. CH\sb4 oxidation was found to occur in all environments regardless of soil moisture. Wet sites were found to have the greatest CH\sb4 oxidation rates, with 20-70% of gross CH\sb4 production being consumed prior to emission. Oxidation within specific sites was found to consume a relatively constant fraction of CH\sb4 despite emissions varying over 3 orders of magnitude, suggesting that methanotrophic activity is dependent upon CH\sb4 source strength. Field and core studies within drier sites suggest a similar pattern, with the dominance of oxidation within dry sites arising from the lack of a significant CH\sb4 source. Conversion of a relatively dry site dominated by CH\sb4 oxidation to a moderate CH\sb4 source at the time of a rising water table agrees well with the stimulation of CH\sb4 production and oxidation observed within a dry bog site following a rain event. Both suggest that dry CH\sb4 sink environments can be converted to CH\sb4 sources with a sufficient increase in soil moisture. Changes in nutrient status have only indirect effects on CH\sb4 oxidation via changes in overall CH\sb4 supply. Significant feedbacks of CH\sb4 emissions to changes in environmental moisture should be expected, with effects of temperature moderating the magnitude of these changes

Solar Driven Gas Phase Advanced Oxidation Processes for Methane Removal – Challenges and Perspectives

Methane (CH(4)) is a potent greenhouse gas and the second highest contributor to global warming. CH(4) emissions are still growing at an alarmingly high pace. To limit global warming to 1.5 °C, one of the most effective strategies is to reduce rapidly the CH(4) emissions by developing large‐scale methane removal methods. The purpose of this perspective paper is threefold. (1) To highlight the technology gap dealing with low concentration CH(4) (at many emission sources and in the atmosphere). (2) To analyze the challenges and prospects of solar‐driven gas phase advanced oxidation processes for CH(4) removal. And (3) to propose some ideas, which may help to develop solar‐driven gas phase advanced oxidation processes and make them deployable at a climate significant scale

Methane emissions from grasslands

IntroductionMethane (CH 4 ) is an important greenhouse gas. The concentration of greenhouse gases in the atmosphere has been increasing since pre-industrial times, mainly due to human activities. This increase gives concern, because it may cause global warming due to an enhanced greenhouse effect.In the soil, CH 4 may be produced under anaerobic conditions, and consumed under aerobic conditions. Net CH 4 emissions, i.e. the resultant of CH 4 exchanges between soil and atmosphere, encompasses the processes CH 4 production, CH 4 consumption, and CH 4 transport. If CH 4 production exceeds CH 4 consumption, the soil is a source of CH 4 ; if CH 4 consumption exceeds CH 4 production, the soil is a sink of CH 4 . The contribution of soils to the global CH 4 balance is significant: 14-47% of the total source and 3-9% of the total sink (IPCC, 1995a).The major aims of this study were to provide insight into the major factors that contribute to net CH 4 emissions from grasslands, and to provide quantitative data on net CH 4 emissions from typical grasslands with a range of soil wetness and N input in the Netherlands. CH 4 emissions from grasslands were measured with flux chambers at a number of sites in the period 1994-1997. Furthermore, several incubation experiments were carried out. Since large variability of net CH 4 emissions is a common phenomenon, special attention was paid to temporal and spatial variability.Wet grasslands with low N input on peat soilsThe area of wet grasslands on peat soil in the Netherlands is small, but slowly increasing at the expense of drained, agriculturally used grasslands. Net CH 4 emissions were measured at wet grasslands on peat soil in the nature preserve "Nieuwkoopse Plassen", which is a former peat mining and agricultural area with narrow grassland and reed fields surrounded by ditches. Ground water level is kept near the surface via the water level of the ditches. Mean ground water level is 10-20 cm below the surface. N input is 30-50 kg N ha -1yr -1via atmospheric deposition. Measurements were carried out at three sites, Drie Berken Zudde, Koole and Brampjesgat, during three years. The sites were considerable sources of CH 4 with average CH 4 emissions of 79, 133 and 204 kg CH 4 ha -1yr -1, respectively. Ditches near the sites emitted 42-225 kg CH 4 ha -1yr -1. The time course of CH 4 emissions for all experimental sites and years was fit with a multiple linear regression model with ground water level and soil temperature as independent variables. Lowering or raising the ground water level by 5 cm could decrease or increase CH 4 emissions by 30-50%. Therefore, ground water level management of these grasslands should be done with care (Chapter 2). Spatial variability of CH 4 emissions was high. Most important determinants of spatial variability were CH 4 production capacity and aboveground biomass of sedges ( Carex spp.). Sedges and other plants may affect CH 4 emissions by stimulating CH 4 transport from anaerobic layers in the soil to the surface and by serving as substrate for methanogens (Chapter 3).In order to improve our understanding of CH 4 emissions, wet peat soils were fractionated into different size and density fractions. Incubation experiments showed that the individual fractions were rather similar with respect to C mineralisation capacity and C/N ratio, but not with respect to CH 4 production capacity. Significant CH 4 production only occurred for fractions with a large particle size. Furthermore, CH 4 production capacity strongly decreased with depth. This indicates that in these wet peat soils recently died plant material is a major substrate for methanogens (Chapter 4).Intensively managed grasslands with a range of N input on drained peat soilsPeat soils are often considered to have a high CH 4 emitting potential, because they are anoxic at shallow depth and have high organic matter contents. In the Netherlands, the majority of the peat soils is drained. Before this study, it was not known whether drained peat soils would be a source or a sink of CH 4 . Net CH 4 emissions from drained peat soils were measured at grasslands at the experimental farm Zegveld with mean ground water levels of 20-40 cm below the surface and an annual N input via fertilisation and atmospheric deposition ranging from 35-460 kg N ha -1yr -1. Net CH 4 emissions from these grasslands were low; they consumed 0.1 to 0.3 kg CH 4 ha -1yr -1. Effect of mean ground water level, in the range of 20-40 cm below the surface, was significant, but small. There were no significant effects of grazing versus mowing and withholding N fertilisation for three years on net CH 4 emissions (Chapter 5).In order to assess the spatial variability and spatial dependence of greenhouse gas emissions (CH 4 , N 2 O, and CO 2 ), and their underlying soil processes and properties, a field campaign was carried out at grasslands on drained peat soil in Fallköping, Sweden. Emissions and potential factors controlling CH 4 emissions were measured on two adjacent sites on two successive days for each site. Spatial variability was analysed using geostatistics. Both sites were small sinks of CH 4 . Spatial variability of emissions was high with coefficients of variation of 50 to 1400%. Emissions either showed a spatial trend or were spatially dependent. However, spatial dependence of emissions showed differences between sites and also between succeeding days. This implies that emissions can not realistically be estimated by the use of geostatistics (Chapter 6).Extensively managed grasslands with low N input on relatively dry soilsTo explore the maximum uptake of atmospheric CH 4 by grasslands in the Netherlands, net CH 4 emissions were measured at extensively managed heather grasslands on sandy soil in Wolfheze with a mean ground water level more than 3 m below the surface and an annual N input via atmospheric deposition of 40 kg N ha -1yr -1. These grasslands consumed 1.1 kg CH 4 ha -1yr -1. Temporal variability of net CH 4 emissions at Wolfheze was related to differences in soil temperature and soil moisture content. CH 4 uptake was highest at high soil temperatures and intermediate soil moisture contents. Incubation experiments showed that at low soil moisture contents, CH 4 consumption was completely inhibited, probably due to physiological water stress of methanotrophs. At high soil moisture contents, CH 4 consumption was greatly reduced, probably due to the slow down of diffusive CH 4 and O 2 transport in the soil. Optimum soil moisture contents were in the same range as prevailing in the field (Chapter 7).Determining factors for CH 4 emissionsImportant environmental factors determining CH 4 emissions are soil organic matter, ground water level, soil moisture content, temperature, and vegetation characteristics. Ground water level exerts a primary control over CH 4 emissions, since ground water level forms the transition zone between anaerobic (potential CH 4 producing) and aerobic (potential CH 4 consuming) layers in the soil. Therefore, drainage of wet grasslands is an important management factor determining CH 4 emissions. At the current rates of N input via fertilisation and atmospheric deposition in the Netherlands, the overall net effect of N fertilisation on net CH 4 emissions from grasslands is small or negligible. Furthermore, the effects of grazing versus mowing and stocking density on net CH 4 emissions are negligible (Chapter 8). In conclusion, grassland management, other than drainage, is not an option to mitigate net CH 4 emissions from grasslands in the Netherlands.Quantification of net CH 4 emissions from grasslands in the NetherlandsMost grasslands in the Netherlands are intensively managed with a total N input via fertilisation and atmospheric deposition in the range of 300-500 kg N ha -1yr -1. Thus far, CH 4 emissions from grasslands in the Netherlands were not well-documented. However, in this study, CH 4 emissions from a number of grasslands with a range of soil wetness and N input have been quantified. Total net CH 4 uptake by grasslands in the Netherlands (excluding wet grasslands) is estimated at 0.5 Gg CH 4 yr -1. Wet soils, which occupy only 0.5% of the total surface area, emit 5-10 Gg CH 4 yr -1. Estimates of CH 4 emissions in the Netherlands should be adjusted to put straight the role of grasslands in the national CH 4 budget.</p

Substantial hysteresis in emergent temperature sensitivity of global wetland CH4_{4} emissions

Wetland methane (CH$_{4}$) emissions (F$_{CH_{4}}$) are important in global carbon budgets and climate change assessments. Currently, F$_{CH_{4}}$ projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent F$_{CH_{4}}$ temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that F$_{CH_{4}}$ are often controlled by factors beyond temperature. Here, we evaluate the relationship between F$_{CH_{4}}$ and temperature using observations from the FLUXNET-CH$_{4}$ database. Measurements collected across the globe show substantial seasonal hysteresis between F$_{CH_{4}}$ and temperature, suggesting larger F$_{CH_{4}}$ sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH$_{4}$ production are thus needed to improve global CH$_{4}$ budget assessments

Potential of alternate wetting and drying irrigation practices for the mitigation of ghg emissions from rice fields: Two cases in central luzon (philippines)

Reducing methane (CH$_{4}$) emission from paddy rice production is an important target for many Asian countries in order to comply with their climate policy commitments. National greenhouse gas (GHG) inventory approaches like the Tier-2 approach of the Intergovernmental Panel on Climate Change (IPCC) are useful to assess country-scale emissions from the agricultural sector. In paddy rice, alternate wetting and drying (AWD) is a promising and well-studied water management technique which, as shown in experimental studies, can effectively reduce CH$_{4}$) emissions. However, so far little is known about GHG emission rates under AWD when the technique is fully controlled by farmers. This study assesses CH$_{4}$) and nitrous oxide (N$_{2}$)O) fluxes under continuous flooded (CF) and AWD treatments for seven subsequent seasons on farmers’ fields in a pumped irrigation system in Central Luzon, Philippines. Under AWD management, CH$_{4}$) emissions were substantially reduced (73% in dry season (DS), 21% in wet season (WS)). In all treatments, CH$_{4}$) is the major contributor to the total GHG emission and is, thus, identified as the driving force to the global warming potential (GWP). The contribution of N$_{2}$)O emissions to the GWP was higher in CF than in AWD, however, these only offset 15% of the decrease in CH$_{4}$) emission and, therefore, did not jeopardize the strong reduction in the GWP. The study proves the feasibility of AWD under farmers’ management as well as the intended mitigation effect. Resulting from this study, it is recommended to incentivize dissemination strategies in order to improve the effectiveness of mitigation initiatives. A comparison of single CH$_{4}$) emissions to calculated emissions with the IPCC Tier-2 inventory approach identified that, although averaged values showed a sufficient degree of accuracy, fluctuations for single measurement points have high variation which limit the use of the method for field-level assessments

Role of C3 plant species on carbon dioxide and methane emissions in Mediterranean constructed wetland

C3 plant species are widely used to vegetate constructed wetlands (CW), but so far no information is available on their effect on CW CO 2(eq) balance in the Mediterranean climate. The aim of this research was to study carbon dioxide (CO 2 ) and methane (CH 4 ) emissions and CO 2(eq) budgets of CW horizontal sub-surface flow pilot-plant beds vegetated with Arundo donax L. and Phragmites australis (Cav.) Trin. ex Steud. compared with an unvegetated bed in Sicily. The highest total plant biomass production was measured in the bed vegetated with A. donax (17.0 kg m –2 ), whereas P. australis produced 7.6 kg m –2 . CO 2 and CH 4 emissions and showed significant correlation with average air temperature and solar radiation for each bed. The CO 2 emission values ranged from 0.8±0.1 g m –2 d –1 , for the unvegetated bed in April, to 24.9±0.6 g m –2 d –1 for the bed with P. australis in August. The average CO 2 emissions of the whole monitored period were 15.5±7.2, 15.1±7.1 and 3.6±2.4 g m –2 d –1 for A. donax , P. australis and unvegetated beds respectively. The CH 4 fluxes differed significantly over the monitored seasons, with the highest median value being measured during spring (0.963 g m –2 d –1 ). No statistical differences were found for CH 4 flux among the studied beds. Cumulative estimated CH 4 emissions during the study period (from April to December) were 159.5, 134.1 and 114.7 g m –2 for A. donax , P. australis and unvegetated beds respectively. CO 2(eq) balance showed that the two vegetated beds act as CO 2(eq) sinks, while the unvegetated bed, as expected, acts as a CO 2(eq) source. Considering only the above-ground plant biomass in the CO 2(eq) budgets, P. australis and A. donax determined uptakes of 1.30 and 8.35 kg CO 2(eq) m –2 respectively

Bovine host genome acts on rumen microbiome function linked to methane emissions

Our study provides substantial evidence that the host genome affects the comprehensive function of the microbiome in the rumen of bovines. Of 1,107/225/1,141 rumen microbial genera/metagenome assembled uncultured genomes (RUGs)/genes identified from whole metagenomics sequencing, 194/14/337 had significant host genomic effects (heritabilities ranging from 0.13 to 0.61), revealing that substantial variation of the microbiome is under host genomic control. We found 29/22/115 microbial genera/RUGs/genes host-genomically correlated (|0.59| to |0.93|) with emissions of the potent greenhouse gas methane (CH(4)), highlighting the strength of a common host genomic control of specific microbial processes and CH(4). Only one of these microbial genes was directly involved in methanogenesis (cofG), whereas others were involved in providing substrates for archaea (e.g. bcd and pccB), important microbial interspecies communication mechanisms (ABC.PE.P), host-microbiome interaction (TSTA3) and genetic information processes (RP-L35). In our population, selection based on abundances of the 30 most informative microbial genes provided a mitigation potential of 17% of mean CH(4) emissions per generation, which is higher than for selection based on measured CH(4) using respiration chambers (13%), indicating the high potential of microbiome-driven breeding to cumulatively reduce CH(4) emissions and mitigate climate change

Association of temperament and acute stress responsiveness with productivity, feed efficiency, and methane emissions in beef cattle: an observational study

The aim of this study was to assess individual differences in temperament and stress response and quantify their impact on feed efficiency, performance, and methane (CH(4)) emissions in beef cattle. Eighty-four steers (castrated males) (Charolais or Luing) were used. Temperament was assessed using two standardized tests: restlessness when restrained [crush score (CS)] and flight speed (FS) on release from restraint. Over a 56-day period individual animal dry matter intake (DMI) and weekly body weight was measured. Ultrasound fat depth was measured at the end of 56 days. Average daily gain (ADG), feed conversion ratio (FCR), and residual feed intake (RFI) were calculated. After the 56-day test period, animals were transported in groups of six/week to respiration chamber facilities. Blood samples were taken before and 0, 3, 6, and 9 h after transport. Plasma cortisol, creatine kinase (CK), glucose, and free fatty acids (FFA) were determined to assess physiological stress response. Subsequently, CH(4) emissions were measured over a 3-day period in individual respiration chambers. CS (1.7 ± 0.09) and FS (1.6 ± 0.60 m/s) were repeatable (0.63 and 0.51, respectively) and correlated (r = 0.36, P < 0.001). Plasma cortisol, CK, and FFA concentrations increased after transport (P = 0.038, P = 0.006, and P < 0.001, respectively). Temperament (CS) and CK concentration were correlated (r = 0.29; P = 0.015). The extreme group analysis reveals that excitable animals (FS; P = 0.032) and higher stress response (cortisol, P = 0.007; FFA, P = 0.007; and CK, P = 0.003) were associated with lower DMI. ADG was lower in more temperamental animals (CS, P = 0.097, and FS, P = 0.030). Fat depth was greater in steers showing calmer CS (P = 0.026) and lower plasma CK (P = 0.058). Temperament did not show any relationship with RFI or CH(4) emissions. However, steers with higher cortisol showed improved feed efficiency (lower FCR and RFI) (P < 0.05) and greater CH(4) emissions (P = 0.017). In conclusion, agitated temperament and higher stress responsiveness is detrimental to productivity. A greater stress response is associated with a reduction in feed intake that may both increase the efficiency of consumed feed and the ratio of CH(4) emissions/unit of feed. Therefore, temperament and stress response should be considered when designing strategies to improve efficiency and mitigate CH(4) emissions in beef cattle

Inverse modelling of CH4 emissions for 2010-2011 using different satellite retrieval products from GOSAT and SCIAMACHY

At the beginning of 2009 new space-borne observations of dry-air column-averaged mole fractions of atmospheric methane (XCH$_{4}$) became available from the Thermal And Near infrared Sensor for carbon Observations–Fourier Transform Spectrometer (TANSO-FTS) instrument on board the Greenhouse Gases Observing SATellite (GOSAT). Until April 2012 concurrent methane (CH$_{4}$) retrievals were provided by the SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) instrument on board the ENVironmental SATellite (ENVISAT). The GOSAT and SCIAMACHY XCH$_{4}$ retrievals can be compared during the period of overlap. We estimate monthly average CH$_{4}$ emissions between January 2010 and December 2011, using the TM5-4DVAR inverse modelling system. In addition to satellite data, high-accuracy measurements from the Cooperative Air Sampling Network of the National Oceanic and Atmospheric Administration Earth System Research Laboratory (NOAA ESRL) are used, providing strong constraints on the remote surface atmosphere. We discuss five inversion scenarios that make use of different GOSAT and SCIAMACHY XCH$_{4}$ retrieval products, including two sets of GOSAT proxy retrievals processed independently by the Netherlands Institute for Space Research (SRON)/Karlsruhe Institute of Technology (KIT), and the University of Leicester (UL), and the RemoTeC “Full- Physics” (FP) XCH$_{4}$ retrievals available from SRON/KIT. The GOSAT-based inversions show significant reductions in the root mean square (rms) difference between retrieved and modelled XCH$_{4}$, and require much smaller bias corrections compared to the inversion using SCIAMACHY retrievals, reflecting the higher precision and relative accuracy of the GOSAT XCH$_{4}$. Despite the large differences between the GOSAT and SCIAMACHY retrievals, 2-year average emission maps show overall good agreement among all satellitebased inversions, with consistent flux adjustment patterns, particularly across equatorial Africa and North America. Over North America, the satellite inversions result in a significant redistribution of CH$_{4}$ emissions from North-East to South-Central United States. This result is consistent with recent independent studies suggesting a systematic underestimation of CH$_{4}$ emissions from North American fossil fuel sources in bottom-up inventories, likely related to natural gas production facilities. Furthermore, all four satellite inversions yield lower CH$_{4}$ fluxes across the Congo basin compared to the NOAA-only scenario, but higher emissions across tropical East Africa. The GOSAT and SCIAMACHY inversions show similar performance when validated against independent shipboard and aircraft observations, and XCH$_{4}$ retrievals available from the Total Carbon Column Observing Network (TCCON)