CH4 Output Research Articles

Temperature Sensitivity of Soil Greenhouse Gas Production in Three High‐Arctic Plant Community Types at Cape Bounty, Nunavut

Enhanced precipitation and higher temperatures are expected in the Arctic as the result of future climatic warming. To understand future contributions of high‐arctic ecosystems to the climate system, we need to understand the feedbacks between climate and greenhouse gas production, and how they might vary between plant community types distributed along soil moisture gradients. We incubated intact soil cores in the laboratory to explore the temperature sensitivity of soil greenhouse gas (CO2, CH4, N2O) production across the three main plant community types of Cape Bounty, Nunavut: polar desert, mesic tundra and wet sedge. Two sets of cores (0‐10 cm mineral soil) were incubated in the laboratory at 4, 8, and 12°C for one month. We also measured plant community differences in soil thermal regimes for one year. Mean field temperatures were highest in the polar desert during the summer months, while temperatures in the mesic tundra were lowest during this time. In the winter, soil temperatures were lowest in the polar desert and highest in the wet sedge communities. Initial incubation results demonstrate Q10 values for CO2 production ranging from 2.18 in wet sedge to 8.67 in polar desert soils. We observed a Q10 of 4.03 for CH4 output in mesic tundra soils and a Q10 of 16.42 for N2O output in wet sedge soils. Our results suggest that use of single Q10 values to predict future greenhouse gas emissions from high‐arctic ecosystems would likely underestimate the contribution of these ecosystems to the global climate system in a warmer climate.

Enhanced substrate degradation and methane yield with maleic acid pre-treatments in biomass crops and residues

Organic acids are envisaged as alternative catalysts to strong mineral acids, in pre-treatment of ligno-cellulosic biomass for anaerobic digestion (AD). To evaluate this hypothesis, an untreated control and four pre-treatments (25 °C for 24 h) involving two levels of maleic acid (34.8 and 69.6 kg m−3), alone and combined with sulphuric acid (4 kg m−3), were studied in three agricultural substrates: Arundo (aka giant reed), Barley straw and B133 fibre sorghum. Methane production was assessed in a batch AD assay (35 °C for 51 days) with 4 g L−1 of volatile solid (VS) load. Fibre composition and structure were investigated through chemical analysis and Fourier transform infrared (FTIR) spectrometry. Arundo and B133 that were the most and least recalcitrant substrate, respectively, staged the highest and lowest increase in methane with high maleic acid: +62% over 218 cm3 g−1 of VS in untreated Arundo; +36% over 284 cm3 g−1 of VS in untreated B133. Barley straw showed an intermediate behaviour (+41% over 269 cm3 g−1 of VS). H2SO4 addition to maleic acid did not improve CH4 output. The large increase in methane yield determined by pre-treatments was reflected in the concurrent decrease of fibre (between 14 and 39% depending on fibrous component). Based on FTIR spectra, bands assigned to hemicellulose and cellulose displayed lower absorbance after pre-treatment, supporting the hypothesis of solubilisation of structural carbohydrates and change in fibre structure. Hence, maleic acid was shown a suitable catalyst to improve biodegradability of ligno-cellulosic biomass, especially in recalcitrant substrates as Arundo.

A comparison of methane emissions from beef cattle measured using methane hoods with those measured using respiration chambers

The methane hood (MH) system is a novel method of quantifying methane (CH4) emissions from cattle during feeding. The MH system measures CH4 concentrations exhausted from beneath a hood designed to partially enclose the volume above a feed bin. To test the system two experiments were conducted on two groups (n=84 and 80) of finishing beef cattle of differing breeds, whereby CH4 measurements taken over 56 days using the MH system were compared to CH4 output measured subsequently on the same animals using respiration chambers (RC). The primary objective of this study was to compare the MH and RC measurements and to develop an equation to predict CH4 measured in RC from measurements taken during group feeding. The second objective was to determine whether the MH system could detect dietary treatment effects from diets designed to reduce CH4 emissions. In experiment 1, cross-bred Charolais and purebred Luing steers were offered 2 contrasting diets consisting of forage to concentrate ratios (g/kg DM) of 500:500 (Mixed, M1) and 80:920 (Concentrate, C1). Within each diet there were 3 treatments: (i) Control, (ii) Nitrate (calcium nitrate with 77% nitrate on a DM basis), and (iii) Rapeseed cake (higher fat content). Both the MH and RC measurements detected differences in CH4 emissions between diets M1 and C1 (P<0.001), and between the Control and Nitrate treatments within diet M1 (P<0.05). In experiment 2, cross-bred Aberdeen Angus and cross-bred Limousin steers received the same Mixed diet (M2) with 4 treatments containing nitrate and/or high oil in a 2×2 factorial arrangement: (i) Control, (ii) Nitrate, (iii) Maize dark grains (higher fat content) and (iv) Combined (both nitrate and higher fat). Again, both the MH and RC measurements detected reductions in CH4 emissions from animals receiving treatments amended with nitrate (P<0.001). However, only the MH measurement technique detected differences when animals received treatments with higher fat contents (P<0.001). Using the CH4 concentrations measured by the MH system and the dry matter intake (DMI) measured during the 56 days test period prediction models for individual animal daily CH4 output were developed and subsequently validated. The best prediction model produced a good correlation between predicted and measured CH4 output (R2=0.77, P<0.001), with a concordance correlation coefficient of 0.84. We conclude that the MH system can be used to estimate the effects of dietary mitigation strategies on CH4 emissions. Furthermore, the predicted CH4 output from MH measurement supports the use of this system as a tool for the genetic selection of cattle based on CH4 emissions.

Analysis of Transient Behavior of Fuel Reformer to Fuel Supply Variation in Solid Oxide Fuel Cell Systems with Anode Off-Gas Recycle

In the case of increasing fuel supply to solid oxide fuel cell (SOFC) systems, mass transport delay generally occurs in reformers and SOFCs. Therefore, heat used for fuel reforming becomes larger than heat supplied to reformers, and reformer heat tends to be absorbed. In this paper, transient behavior of reformers in SOFC systems with anode off-gas recycle, in the case of increasing fuel supply, is analyzed by numerical simulation. As a result, it is suggested that reformer temperature decreases from several to several tens of K, when heat is absorbed from the reformer, which is small scale, lightweight and has low heat capacity, for several seconds. In addition, methane flow rate outputted from the reformer increases, and carbon deposition occurs, depending on conditions. This paper will present details of these results and discuss methods to prevent carbon deposition and increase of CH4 output from the reformer.

Estimates of repeatability and heritability of methane production in sheep using portable accumulation chambers

This study was designed to screen a large number of sheep to identify individuals with high and low methane (CH4) production, and to estimate repeatability and heritability of CH4 emissions in sheep, utilising portable accumulation chambers (PAC) designed for in-field use. Mature ewes (n = 710) selected from a research flock with known sires had their CH4 production over 1 h measured in PAC [CH4 (g1h)]. Individuals with High (n = 103) or Low (n = 104) CH4 (g1h), adjusted for liveweight (LW), were selected and re-measured on three occasions 1–4 months later, at another site with more abundant and better quality pasture. Mean of the selected (207) ewes CH4 (g1h) emissions were ~50% higher than at the first measurement site (0.66 g vs 0.42 g). LW was a significant correlate of CH4 production (r = 0.47). Correlations between CH4 (g1h) for the three PAC measurements at Site 2, before adjusting for LW ranged from 0.44 to 0.55. After adjusting for the effect of LW, repeatability was 0.33 at the first and 0.43 at the second site. The correlation between estimates of an animal’s emissions at the first and second sites, adjusted for LW, was 0.24. Initial CH4 production of the selected High group was 32% greater than the Low group (P &lt; 0.0001). On re-measurement there was still a significant difference (9–15%, P &lt; 0.006) between Low and High groups. The initial estimate of heritability of CH4 (g1h), based on variation between the ewes’ sires (0.13), was not maintained across the two sites. This may be due to genotype × environment interactions. We postulate that aspects of rumen physiology, which modulate CH4 production, could be expressed differently in different nutritional environments. Our results indicate that field use of PAC to screen sheep populations for CH4 production is both robust and repeatable. However, further investigations are required into the relationship between CH4 output of individual animals in PAC compared with the more controlled conditions in respiration chambers.

Effect of dietary supplementation with resveratrol on nutrient digestibility, methanogenesis and ruminal microbial flora in sheep.

Two experiments were conducted to evaluate the effect of resveratrol on methanogenesis and microbial flora in Dorper×thin-tailed Han cross-bred ewes. In experiment 1, ten ewes (67.2±2.24kg BW) were assigned to two dietary treatments, a basal diet and a basal diet supplemented with resveratrol (0.25g/head·day), to investigate the effect of resveratrol on nutrient digestibility and nitrogen balance. In experiment 2, six ewes (64.0±1.85kg BW) with ruminal cannulae were assigned to the identical dietary treatments used in experiment 1 to investigate supplementary resveratrol on ruminal fermentation and microbial flora using qPCR. The results showed that supplementary resveratrol improved the digestibility of organic matter (OM; p<0.001), nitrogen (N; p=0.007), neutral detergent fibre (NDF; p<0.001) and acid detergent fibre (ADF; p<0.001). The excretion of faecal N was reduced (p=0.007), whereas that of urinary N increased (p=0.002), which led to an unchanged N retention (p=0.157). Both CO2 and CH4 output scaled to digestible dry matter (DM) intake decreased from 602.5 to 518.7 (p=0.039) and 68.2 to 56.6 (p<0.001) respectively. Ruminal pH (p=0.341), ammonia (p=0.512) and total volatile fatty acid (VFA) (p=0.249) were unaffected by resveratrol. The molar proportion of propionate increased from 13.1 to 17.5% (p<0.001) while that of butyrate decreased from 11.0 to 9.55% (p<0.001). The ratio of acetate to propionate (A/P) decreased from 5.44 to 3.96 (p<0.001). Supplementary resveratrol increased ruminal population of Fibrobacter succinogenes, Ruminococcus albus and Butyrivibrio fibrisolvens (p<0.001) while decreased protozoa and methanogens. In conclusion, dietary resveratrol inhibited methanogenesis without adversely affecting ruminal fermentation.

Effect of sprouted barley grain supplementation of an herbage-based or haylage-based diet on ruminal fermentation and methane output in continuous culture

A 4-unit dual-flow continuous-culture fermentor system was used to assess the effect of supplementing 7-d sprouted barley (SB) or barley grain (BG) with an herbage-based or haylage-based diet on nutrient digestibility, volatile fatty acid (VFA) profiles, bacterial protein synthesis, and methane (CH4) output. Treatments were randomly assigned to fermentors in a 4×4 Latin square design with a 2×2 factorial arrangement using 7 d for diet adaptation and 3 d for sample collection. Experimental diets were (1) 55.5g of herbage dry matter (DM) + 4.5g of SB DM, (2) 56.0g of herbage DM + 4.0g of BG DM, (3) 55.5g of haylage DM + 4.5g of SB DM, and (4) 56.0g of haylage DM + 4.0g of BG DM. Forages were fed at 0730, 1030, 1400, and 1900h, whereas SB and BG were fed at 0730 and 1400h. Gas samples for CH4 analysis were collected at 0725, 0900, 1000, 1355, 1530, and 1630h on d 8, 9, and 10. Fluid samples were taken once daily on d 8, 9, and 10 for pH measurements and for ammonia-N and VFA analysis and analyzed for DM, organic matter, crude protein, neutral detergent fiber, and acid detergent fiber for determination of nutrient digestibilities and estimation of bacterial protein synthesis. Orthogonal contrasts were used to compare the effect of forage source (haylage vs. herbage), supplement (BG vs. SB), and the forage × supplement interaction. Apparent and true DM and organic matter digestibilities as well as apparent crude protein digestibility were not affected by forage source. However, true DM digestibility was greatest for diets supplemented with SB. Apparent neutral and acid detergent fiber digestibilities of herbage-based diets were higher than haylage-based diets but fiber digestibility was not affected by supplement. Diets supplemented with SB had higher mean and minimum pH than BG; however, maximum pH was not affected by diet. Supplementation with BG produced a greater concentration of total VFA compared with diets supplemented with SB. Haylage-based diets produced greater CH4 output compared with herbage-based diets but supplementation did not affect CH4 output. Efficiency of bacterial protein synthesis was greater for herbage-based diets compared with haylage-based diets, with no effect of supplementation. Overall, supplementation with SB marginally increased true DM digestibility of herbage- and haylage-based diets but did not affect fiber and crude protein digestibilities, CH4 output, and bacterial efficiency, compared with BG.

Methane emissions among individual dairy cows during milking quantified by eructation peaks or ratio with carbon dioxide

The aims of this study were to compare methods for examining measurements of CH4 and CO2 emissions of dairy cows during milking and to assess repeatability and variation of CH4 emissions among individual dairy cows. Measurements of CH4 and CO2 emissions from 36 cows were collected in 3 consecutive feeding periods. In the first period, cows were fed a commercial partial mixed ration (PMR) containing 69% forage. In the second and third periods, the same 36 cows were fed a high-forage PMR ration containing 75% forage, with either a high grass silage or high maize silage content. Emissions of CH4 during each milking were examined using 2 methods. First, peaks in CH4 concentration due to eructations during milking were quantified. Second, ratios of CH4 and CO2 average concentrations during milking were calculated. A linear mixed model was used to assess differences between PMR. Variation in CH4 emissions was observed among cows after adjusting for effects of lactation number, week of lactation, diet, individual cow, and feeding period, with coefficients of variation estimated from variance components ranging from 11 to 14% across diets and methods of quantifying emissions. No significant difference was detected between the 3 PMR in CH4 emissions estimated by either method. Emissions of CH4 calculated from eructation peaks or as CH4 to CO2 ratio were positively associated with forage dry matter intake. Ranking of cows according to CH4 emissions on different diets was correlated for both methods, although rank correlations and repeatability were greater for CH4 concentration from eructation peaks than for CH4-to-CO2 ratio. We conclude that quantifying enteric CH4 emissions either using eructation peaks in concentration or as CH4-to-CO2 ratio can provide highly repeatable phenotypes for ranking cows on CH4 output.

Does diverse grazing behavior of suckler cows have an impact on predicted methane emissions?1

A modeling study based on a dataset from a large-scale grazing study was used to identify the potential impact of grazing behavior and performance of diverse cow genotypes on predicted methane (CH4) emissions. Lactating cows grazing extensive seminatural grassland and heath vegetation were monitored with Global Positioning System collars and activity sensors. The diet selected by cows of 3 different genotypes, Aberdeen Angus cross Limousin (AxL), Charolais (CHA), and Luing (LUI), was simulated by matching their locations during active periods with hill vegetation maps. Measured performance and activity were used to predict energy requirements, DMI, and CH4 output. The cumulative effect of actual performance, diet selection, and actual physical activity on potential CH4 output and yield was estimated. Sensitivity analyses were performed for the digestibility of intake, energy cost of activity, proportion of milk consumed by calves, and reproductive efficiency. Although with a better performance (P < 0.05), LUI required less total energy than the other genotypes (P < 0.001) as the other 2 spent more energy for maintenance (P < 0.001) and activity (P < 0.001). By selecting a better quality diet (P < 0.03), estimated CH4 of CHA cow-calf pairs was lower than AxL (P = 0.001) and slightly lower than LUI (P = 0.08). Energy lost as CH4 was 0.17 and 0.58% lower for LUI than AxL and CHA (P < 0.002). This study suggests for the first time that measured activity has a major impact on estimated CH4 outputs. A 15% difference of the cow-calf pair CH4 was estimated when using different coefficients to convert actual activity into energy. Predicted CH4 was highly sensitive to small changes in diet quality, suggesting the relative importance of diet selection on heterogeneous rangelands. Extending these results to a farm systems scale, CH4 outputs were also highly sensitive to reductions in weaning rates, illustrating the impact on CH4 at the farm-system level of using poorly adapted genotypes on habitats where their performances may be compromised. This paper demonstrates that variations in grazing behavior and grazing choice have a potentially large impact on CH4 emissions, illustrating the importance of including these factors in calculating realistic national and global estimates.

SPECIAL TOPICS — Mitigation of methane and nitrous oxide emissions from animal operations: III. A review of animal management mitigation options1

The goal of this review was to analyze published data on animal management practices that mitigate enteric methane (CH4) and nitrous oxide (N2O) emissions from animal operations. Increasing animal productivity can be a very effective strategy for reducing greenhouse gas (GHG) emissions per unit of livestock product. Improving the genetic potential of animals through planned cross-breeding or selection within breeds and achieving this genetic potential through proper nutrition and improvements in reproductive efficiency, animal health, and reproductive lifespan are effective approaches for improving animal productivity and reducing GHG emission intensity. In subsistence production systems, reduction of herd size would increase feed availability and productivity of individual animals and the total herd, thus lowering CH4 emission intensity. In these systems, improving the nutritive value of low-quality feeds for ruminant diets can have a considerable benefit on herd productivity while keeping the herd CH4 output constant or even decreasing it. Residual feed intake may be a tool for screening animals that are low CH4 emitters, but there is currently insufficient evidence that low residual feed intake animals have a lower CH4 yield per unit of feed intake or animal product. Reducing age at slaughter of finished cattle and the number of days that animals are on feed in the feedlot can significantly reduce GHG emissions in beef and other meat animal production systems. Improved animal health and reduced mortality and morbidity are expected to increase herd productivity and reduce GHG emission intensity in all livestock production systems. Pursuing a suite of intensive and extensive reproductive management technologies provides a significant opportunity to reduce GHG emissions. Recommended approaches will differ by region and species but should target increasing conception rates in dairy, beef, and buffalo, increasing fecundity in swine and small ruminants, and reducing embryo wastage in all species. Interactions among individual components of livestock production systems are complex but must be considered when recommending GHG mitigation practices.

The impact of Lactobacillus plantarum TUA1490L supernatant on in vitro rumen methanogenesis and fermentation

This study investigated the suppression of in vitro rumen methane (CH4) output by the supernatant of Lactobacillus plantarum TUA1490L. Hydrogen peroxide (H2O2) was detected in the supernatant. Although CH4 output was reduced by 72%, the supernatant had an adverse effect on total volatile fatty acid (VFA) concentration.

Replacing alfalfa silage with corn silage in dairy cow diets: Effects on enteric methane production, ruminal fermentation, digestion, N balance, and milk production

The objective of this study was to determine the effects of replacing alfalfa silage (AS) with corn silage (CS) in dairy cow total mixed rations (TMR) on enteric CH4 emissions, ruminal fermentation characteristics, apparent total-tract digestibility, N balance, and milk production. Nine ruminally cannulated lactating cows were used in a replicated 3×3 Latin square design (32-d period) and fed (ad libitum) a TMR [forage:concentrate ratio of 60:40; dry matter (DM) basis], with the forage portion consisting of either alfalfa silage (0% CS; 56.4% AS in the TMR), a 50:50 mixture of both silages (50% CS; 28.2% AS and 28.2% CS in the TMR), or corn silage (100% CS; 56.4% CS in the TMR). Increasing the CS proportion (i.e., at the expense of AS) in the diet was achieved by decreasing the corn grain proportion and increasing that of soybean meal. Intake of DM and milk yield increased quadratically, whereas DM digestibility increased linearly as the proportion of CS increased in the diet. Increasing the dietary CS proportion resulted in changes (i.e., lower ruminal pH and acetate:propionate ratio, reduced fiber digestibility, decreased protozoa numbers, and lower milk fat and higher milk protein contents) typical of those observed when cows are fed high-starch diets. A quadratic response in daily CH4 emissions was observed in response to increasing the proportion of CS in the diet (440, 483, and 434 g/d for 0% CS, 50% CS, and 100% CS, respectively). Methane production adjusted for intake of DM, and gross or digestible energy was unaffected in cows fed the 50% CS diet, but decreased in cows fed the 100% CS diet (i.e., quadratic effect). Increasing the CS proportion in the diet at the expense of AS improved N utilization, as reflected by the decreases in ruminal NH3 concentration and manure N excretion, suggesting low potential NH3 and N2O emissions. Results from this study, suggest that total replacement of AS with CS in dairy cow diets offers a means of decreasing CH4 output and N losses. However, the reduction in fiber degradation and the resulting increase in volatile solids content of the manure may lead to increased CH4 emissions from manure storage.

Representation of a mathematical model to predict methane output in dairy goats

Ruminants may contribute to global warming through the release of methane (CH4) gas by enteric fermentation. Most CH4 emissions from ruminants are estimated using simple regression equations. Thus a mechanistic dynamic model to predict CH4 output by goats was developed by using a computer-aided simulation device via object-oriented modeling. The model was structured into seven stocks; body weight, feed, metabolism, milk, methane and reserves (with two stocks). The goat model was set up to simulate indoor facilities in which the goat was fed a mixed ration. Then, 24 goats were used to evaluate the model during 150days of lactation. A calorimetry system based on an open circuit respiration mask was used for quantification of respiratory CH4 production, as a way to validate the CH4 simulated. The mathematical simulation model estimated an average CH4 conversion factor (Ym) value of 5.3%, and an average daily CH4 production of 1.55MJ/d. The average daily CH4 production for the validation group of goats was 1.51MJ/d. Based on our simulation over 5months of lactation for a mixed diet, use of the Intergovernmental Panel for Climate Change values (Ym=6.5) could result in an overestimation of enteric CH4 for dairy goats fed concentrate diets.

In vitro rumen methane output of grasses and grass silages differing in fermentation characteristics using the gas‐production technique (GPT)

AbstractThe chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH4) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (P &lt; 0·01) the in vitro rumen CH4 output (mL CH4 g−1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (P &lt; 0·05) and higher propionic (P &lt; 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g−1 DM). The magnitude of the decrease in CH4 output (mL g−1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH4 output (mL g−1 DM).

Effect of incremental flaxseed supplementation of an herbage diet on methane output and ruminal fermentation in continuous culture

A 4-unit dual-flow continuous culture fermentor system was used to assess the effect of increasing flaxseed (Linum usitatissimum) supplementation of an herbage-based diet on nutrient digestibility, microbial N synthesis, and methane (CH4) output. Treatments were randomly assigned to fermentors in a 4×4 Latin square design, with 7d for diet adaptation and 3d for data and sample collection. Treatments were 0, 5, 10, and 15% ground flaxseed supplementation of an orchardgrass (Dactylis glomerata L.) diet [70g of total dry matter (DM) fed daily]. Samples were collected from the fermentors 4 times daily at feeding (0730, 1030, 1400, and 1900h) on d 8 to 10 of each of four 10-d periods and analyzed for pH, ammonia-N, and volatile fatty acids. Gas samples for CH4 analysis were collected immediately before and 1 and 2h after the 0730h feeding on d 8, 9, and 10 and at the 1400h feeding on d 7, 8, and 9 of each period. Effluents were analyzed for DM, organic matter, crude protein, and neutral detergent fiber for determination of nutrient digestibilities, and for total purine concentration for estimation of microbial protein synthesis. Apparent DM, organic matter, and neutral detergent fiber digestibilities decreased linearly with increasing supplemental flaxseed, whereas true DM and organic matter digestibilities were not significantly affected by treatment, averaging 77.6 and 79.1%, respectively. Mean ruminal pH and concentration of total volatile fatty acids were not significantly affected by increasing the dietary concentration of flaxseed, averaging 6.68 and 55.9mmol/L across treatments, respectively. However, molar proportions of acetate and propionate increased linearly, whereas those of butyrate and valerate decreased linearly with increasing flaxseed supplementation. Although CH4 output decreased linearly as supplemental flaxseed increased from 0 to 15% of diet DM, ammonia-N concentration, apparent crude protein digestibility, and microbial N synthesis did not differ across treatments. Incremental ground flaxseed supplementation of an herbage-based diet resulted in a corresponding decrease in CH4 output in a dual-flow continuous culture fermentor system. However, apparent nutrient digestibility also decreased with flaxseed supplementation, which, at the cow level, could result in decreased DM intake, milk production, or both.

The Study of Suction Test and Engineering Parameters of Yantai Domestic Garbage Municipal Treatment Plant

This paper gives an analysis of CH4 output of Yantai domestic garbage municipal treatment plant through field static test and dynamic suction test. The former test measures the methane density of the domestic garbage in the landfill area which shows that the area is in the prime time of gas production, while the dynamic test results provide technical parameters for the engineering of the collection and usage of CH4 gas.

A life cycle assessment of seasonal grass-based and confinement dairy farms

Life cycle assessment (LCA) is a holistic systems approach that aims to assess the environmental impacts (potential pollutants and resource use) of the production of goods and services. The aim of this study was to develop an LCA model to compare contrasting milk production systems, a seasonal pasture-based dairy farm and a confinement dairy farm. The environmental impacts considered were global warming, eutrophication, acidification, land use and non-renewable energy use. The LCA estimated on-farm, off-farm (pollutants and resources associated with the production and supply of purchased farm inputs) and total (on-farm and off-farm) environmental impacts. Environmental impacts were quantified per unit of milk and per unit area. The study only considered two research farms, because high quality data were unavailable for a large number of farms. Thus, this was not a representative LCA comparison. The genetic merit of cows modelled was similar for each system. A total mixed ration was fed in the confinement system and grazed grass was mainly fed in the grass-based system. Research data were used to confirm simulated dry matter intake (DMI) and predicted enteric CH4 output from simulated DMI. The study found that when expressed per unit of milk and per on-farm area, all total environmental impacts were greater for the confinement system compared to the grass-based system. Per total farm area (on-farm and off-farm area), all environmental impacts except global warming were lower for the grass-based system. The greater environmental impact of the confinement dairy system was due to the greater use of concentrate feed and the longer manure storage period. Scenario modelling demonstrated that there is potential to decrease the environmental impact of dairy systems, particularly the confinement system, by reducing the use of concentrate ingredients with a high environmental impact and by storing manure in solid systems. Scenario modelling also showed that assumptions regarding the carbon cycle should be clearly outlined when assessing milk production systems and that standardisation of LCA allocation procedures is required. This LCA study is one of the few to directly compare the environmental impact of a grass-based and a confinement dairy system. However direct comparisons are needed, using an LCA methodology such as described in this paper, and using data from a greater number of farms so that each system is better represented thereby ensuring a robust comparison of the two systems on a regional or national basis.

In vitro rumen methane output of perennial ryegrass varieties and perennial grass species harvested throughout the growing season

AbstractThe selection and feeding of perennial ryegrass (Lolium perenne L.) varieties (PRV) or perennial grass species (PGS) may affect enteric methane (CH4) output because of changes in the fermentation dynamics in the rumen as a result of differences in herbage chemical composition. The objective of this study was to determine the effects of PRV and PGS harvested throughout the growing season on herbage chemical composition, and in vitro rumen fermentation variables and CH4 output per unit of feed using a batch culture technique. Seven PRV (Experiment 1: Alto, Arrow, Bealey, Dunluce, Greengold, Malone, Tyrella) and six perennial grasses [Experiment 2: perennial ryegrass (Navan), perennial ryegrass (Portstewart), cocksfoot, meadow fescue, tall fescue, timothy; defined as PGS], managed under a simulated grazing regime, were incubated for 24 h with buffered rumen fluid in two separate experiments. The CH4 output per unit of feed dry‐matter (DM) incubated was not affected (P &gt; 0·05) by PRV (range of mean values across PRV of 23·9–25·3 (SEM 0·41) mL g−1 DM) or by PGS (25·6–26·6 (SEM 0·37) mL g−1 DM). The CH4 output per unit feed DM disappearing during the in vitro rumen incubation was not affected by PRV (33·9–35·1 (SEM 0·70) mL g−1 DM), and although there was an overall PGS effect (P &lt; 0·05; 37·2–40·3 (SEM 0·71) mL g−1 DM), none of the paired contrasts between PGS were significant when analysed using Tukey adjusted comparisons. This outcome reflected either small‐scale or a lack of treatment effects on individual herbage chemical composition (e.g. 454–483 g NDF kg−1 DM, 215–224 g CP kg−1 DM and 94–122 g water‐soluble carbohydrate (WSC) kg−1 DM across PRV; 452–506 g NDF kg−1 DM, 208–243 g CP kg−1 DM and 73–131 g WSC kg−1 DM across PGS) and in vitro rumen fermentation variables. Hence, these results provide no encouragement that choices among the grasses examined, produced within the management regimes operated, would reduce enteric CH4 output per unit of feed in vivo. However, the technique utilized did not take account of animal × PRV or PGS interactions, such as potential differences in intake between animals, that may occur under farm conditions.

The in vitro rumen methane output of perennial grass species and white clover varieties, and associative effects for their binary mixtures, evaluated using a batch-culture technique

Grassland swards containing white clover varieties (WCV) may result in lower enteric methane (CH4) output from grazing ruminants than swards of only perennial grass species (PGS) due to differences in their chemical composition and rumen fermentation dynamics. The objectives of the present study were to compare the chemical composition, in vitro rumen fermentation variables and CH4 output per unit of feed for a range of common PGS and WCV harvested in May from simulated grazing regimes, and to determine the effects of binary mixtures of the PGS and WCV on in vitro rumen fermentation variables and CH4 output, using a batch-culture technique. Four PGS (perennial ryegrass, cocksfoot, meadow fescue and timothy) and three WCV (Aran, Chieftain and Crusader) were incubated as sole substrates or as part of binary mixtures (PGS : WCV ratios of 0 : 1, 0.25 : 0.75, 0.5 : 0.5, 0.75 : 0.25 and 1 : 0) for 24 h at 39°C with buffered rumen fluid. All WCV had lower (P &lt; 0.001) CH4 output per unit of apparent DM disappeared (aDMD; mean value across WCV (s.e.m.) of 27.0 (1.35) mL/g aDMD v. 36.1 (0.90) mL/g aDMD across PGS) during the in vitro rumen incubation than did all PGS. The WCV also had lower CH4 output per unit of total volatile fatty acids (corresponding values of 0.147 (0.0090) v. 0.199 (0.0073) mmol/mmol total volatile fatty acid output) and per unit of total gas produced (0.118 (0.0022) v. 0.153 (0.0024) mmol/mmol total gas produced) than did the PGS. In addition, Aran and Crusader had lower (P &lt; 0.001) CH4 output per unit of feed DM incubated than did all PGS. There were synergistic associative effects (i.e. where the response was greater for the mixtures than the arithmetic calculation using the responses for PGS and WCV alone; P &lt; 0.05) of mixing the PGS and WCV in binary combinations on all CH4 output variables.

Genetic parameters for predicted methane production and potential for reducing enteric emissions through genomic selection

Mitigation of enteric methane (CH4) emission in ruminants has become an important area of research because accumulation of CH4 is linked to global warming. Nutritional and microbial opportunities to reduce CH4 emissions have been extensively researched, but little is known about using natural variation to breed animals with lower CH4 yield. Measuring CH4 emission rates directly from animals is difficult and hinders direct selection on reduced CH4 emission. However, improvements can be made through selection on associated traits (e.g., residual feed intake, RFI) or through selection on CH4 predicted from feed intake and diet composition. The objective was to establish phenotypic and genetic variation in predicted CH4 output, and to determine the potential of genetics to reduce methane emissions in dairy cattle. Experimental data were used and records on daily feed intake, weekly body weights, and weekly milk production were available from 548 heifers. Residual feed intake (MJ/d) is the difference between net energy intake and calculated net energy requirements for maintenance as a function of body weight and for fat- and protein-corrected milk production. Predicted methane emission (PME; g/d) is 6% of gross energy intake (Intergovernmental Panel on Climate Change methodology) corrected for energy content of methane (55.65kJ/g). The estimated heritabilities for PME and RFI were 0.35 and 0.40, respectively. The positive genetic correlation between RFI and PME indicated that cows with lower RFI have lower PME (estimates ranging from 0.18 to 0.84). Hence, it is possible to decrease the methane production of a cow by selecting more-efficient cows, and the genetic variation suggests that reductions in the order of 11 to 26% in 10 yr are theoretically possible, and could be even higher in a genomic selection program. However, several uncertainties are discussed; for example, the lack of true methane measurements (and the key assumption that methane produced per unit feed is not affected by RFI level), as well as the limitations of predicting the biological consequences of selection. To overcome these limitations, an international effort is required to bring together data on feed intake and methane emissions of dairy cows.