Methane Emission Intensity Research Articles

PSI-23 Growth implants can decrease enteric methane emissions intensity from finishing beef cattle

Abstract Growth promotants are a useful tool in cattle production to improve their environmental impact by decreasing emissions per unit of gain and increasing overall feed efficiency. The objective of this study was to assess the relationship between enteric methane emissions, feed intake, average daily gain (ADG), and feed efficiency of implanted and nonimplanted finishing steers. Cattle (n = 62) were housed at the Climate Smart Research pens at Colorado State University and blocked by body weight (BW) into two pens and randomly assigned to treatment. Each pen was equipped with GreenFeed automated head chambers and SmartFeed feed intake measurement (C-Lock, Rapids City, SD). The study was a completely randomized block design. Animals within each block were then randomly assigned a treatment: implanted with Component TE200 (IMP; Elanco Animal Health, Greenfield, IN) or not implanted (CON). Enteric emissions, dry matter feed intake, BW, and BW gain (ADG) were collected from each individual animal from the light and heavy blocks for 80 and 52 d, respectively. Data were analyzed in JMP Pro with the linear model function and significance was declared a P ≤ 0.05. IMP cattle had a greater average ADG (2.40 kg/d vs 1.77 kg/d, P < 0.0001) compared with CON cattle. A difference was observed in total methane (CH4) emissions between treatments (200.83 g CH4/d IMP and 187.45 g CH4/d CON, P = 0.02). Dry matter intake (DMI) was not different between treatments (P = 0.17). Methane emissions intensity for each treatment was 84.89 (IMP) and 106.90 g/kg of ADG (CON) was different (P = 0.0002), while CH4 yield (CH4 per kg of DMI) was not different (P = 0.12). Overall feed efficiency between treatments resulted in IMP animals having a greater feed efficiency (4.74 kg DM/kg ADG) compared with CON animals (6.32 kg DM/kg ADG, P < 0.0001). In summary, growth promotants decrease CH4 emissions intensity in finishing steers and increase animal feed efficiency without affecting daily DMI.

High-resolution satellite estimates of coal mine methane emissions from local to regional scales in Shanxi, China

Coal mines are significant anthropogenic sources of methane emissions, detectable and traceable from high spatial resolution satellites. Nevertheless, estimating local or regional-scale coal mine methane emission intensities based on high-resolution satellite observations remains challenging. In this study, we devise a novel interpolation algorithm based on high-resolution satellite observations (including Gaofen5-01A/02, Ziyuan-1 02D, PRISMA, GHGSat-C1 to C5, EnMAP, and EMIT) and conduct assessments of annual mean coal mine methane emissions in Shanxi Province, China, one of the world's largest coal-producing regions, spanning the period 2019 to 2023 across various scales: point-source, local, and regional. We use high-resolution satellite observations to perform interpolation-based estimations of methane emissions from three typical coal-mining areas. This approach, known as IPLTSO (Interpolation based on Satellite Observations), provides spatially explicit maps of methane emission intensities in these areas, thereby providing a novel local-scale coal mine methane emission inventory derived from high-resolution top-down observations. For regional-scale estimation and mapping, we utilize high-resolution satellite data to complement and substitute facility-level emission inventories for interpolation (IPLTSO+GCMT, Interpolation based on Satellite Observations and Global Coal Mine Tracker). We evaluate our IPLTSO and IPLTSO+GCMT estimation with emission inventories, top-down methane emission estimates from TROPOMI observations, and TROPOMI's methane concentration enhancements. The results suggest a notable right-skewed distribution of methane emission flux rates from coal mine point sources. Our IPLTSO+GCMT estimates the annual average coal mine methane emission in Shanxi Province from 2019 to 2023 at 8.9 ± 0.5 Tg/yr, marginally surpassing top-down inversion results from TROPOMI (8.5 ± 0.6 Tg/yr in 2019 and 8.6 ± 0.6 Tg/yr in 2020). Furthermore, the spatial patterns of methane emission intensity delineated by IPLTSO+GCMT and IPLTSO closely mirror those observed in TROPOMI's methane enhancements. Our comparative assessment underscores the superior performance and substantial potential of the developed interpolation algorithm based on high-resolution satellite observations for multi-scale estimation of coal mine methane emissions.

Grid study on methane diffusion law in confined space of working face

AbstractThe layout of methane sensors in the working face cannot meet the needs for monitoring methane concentrations within confined spaces, and it is challenging to determine the precise locations for manual inspections. Therefore, the working face is firstly divided into different areas and grids. Then combined with the characteristics of methane emissions and the measured data on site, the boundary conditions of simulation experiments are set up and the research is carried out on the diffusion law of methane in the confined space of the working face under different conditions. The experimental results show that methane emission intensity from coal walls affects its distribution. As emission intensity rises, methane nearer the coal wall decreases, while methane further away increases. Among coal mining points, point 2 shows the widest methane diffusion range. Rising wind speeds decrease methane diffusion from the coal wall, increasing vertical diffusion distance. Methane from the coal wall shifts to the air inlet, while methane from the mining point diffuses increasingly to the downwind side. The location of the maximum methane concentration generated from falling coal and its transportation process is only related to the location of the coal mining point. The key areas for methane monitoring in confined spaces of the working face should be the overlapping locations of the vertical‐3 and vertical‐4 areas and the horizontal‐1 and horizontal‐3 areas. The key areas for manual inspection should be the overlapping locations of the vertical‐2 and vertical‐3 areas and the horizontal‐1 area.

A meta-analysis of probiotic interventions to mitigate ruminal methane emissions in cattle: implications for sustainable livestock farming

In recent years, the significant impact of ruminants on methane emissions has garnered international attention. While dietary strategies have been implemented to solve this issue, probiotics gained the attention of researchers due to their sustainability. However, it is challenging to ascertain their effectiveness as an extensive range of strains and doses have been reported in the literature. Hence, the objective of this experiment was to perform a meta-analysis of probiotic interventions aiming to reduce ruminal methane emissions from cattle. From 362 articles retrieved from scientific databases, 85 articles were assessed independently by two reviewers, and 20 articles representing 49 comparisons were found eligible for meta-analysis. In each study, data such as mean, SD, and sample sizes of both the control and probiotic intervention groups were extracted. The outcomes of interest were methane emission, methane yield, and methane intensity. For the meta-analysis, effect sizes were pooled using a fixed effect or a random effect model depending on the heterogeneity. Afterward, sensitivity analyses were conducted to confirm the robustness of the findings. Overall pooled standardized mean differences (SMDs) with their confidence intervals (CIs) did not detect significant differences in methane emission (SMD = −0.04; 95% CI = −0.18–0.11; P = 0.632), methane yield (SMD = −0.08; 95% CI = −0.24–0.07; P = 0.291), and methane intensity (SMD = −0.22; 95% CI = −0.50–0.07; P = 0.129) between cattle supplemented with probiotics and the control group. However, subgroup analyses revealed that multiple-strain bacterial probiotics (SMD = −0.36; 95% CI = −0.62 to −0.11; P = 0.005), specifically the combination of bacteria involved in reductive acetogenesis and propionate production (SMD = −0.71; 95% CI = −1.04 to −0.36; P = 0.001), emerged as better interventions. Likewise, crossbreeds (SMD = −0.48; 95% CI = −0.78 to −0.18; P = 0.001) exhibited a more favorable response to the treatments. Furthermore, meta-regression demonstrated that longer periods of supplementation led to significant reductions in methane emissions (P = 0.001), yield (P = 0.032), and intensity (P = 0.012) effect sizes. Overall, the results of the current study suggest that cattle responses to probiotic interventions are highly dependent on the probiotic category. Therefore, extended trials performed with probiotics containing multiple bacterial strains are showing the most promising results. Ideally, further trials focusing on the use of probiotics to reduce ruminal methane in cattle should be conducted to complete the available literature.

Methane emissions intensity in grazing dairy cows fed graded levels of concentrate pellets

ABSTRACT The current New Zealand greenhouse gas inventory predictions assume that dairy cows consume pasture only, but the use of supplemental feeds, including concentrates, on New Zealand dairy farms has increased greatly in recent decades. The objective of this study was to evaluate the effect of feeding graded levels of concentrates on methane (CH4) emissions in lactating dairy cows within a pastoral system. Early lactation dairy cows (n = 72) were allocated (n = 18 per treatment) to receive 0, 2, 4 and 6 kg dry matter (DM) of treatment concentrates per day during milking. The cows grazed pasture ad libitum and CH4 emissions were measured in the paddocks using automated emissions monitoring systems called ‘GreenFeed’. Gross CH4 emissions (g/d) were similar for cows across the four dietary treatments, while CH4 emissions intensity (g/kg fat and protein corrected milk production (FPCM) and milk solids production) linearly decreased with increasing concentrate inclusion in the diet (P < 0.02). The CH4 intensity decreased linearly (r 2 = 0.42) and quadratically (r 2 = 0.53) with increasing FPCM production.

Lactational performance, rumen fermentation, nutrient use efficiency, enteric methane emissions, and manure greenhouse gas-emitting potential in dairy cows fed a blend of essential oils

The objective of this experiment was to investigate the effects of an essential oil (EO) blend on lactational performance, rumen fermentation, nutrient utilization, blood variables, enteric methane emissions and manure greenhouse gas-emitting potential in dairy cows. A randomized complete block design experiment was conducted with 26 primiparous and 22 multiparous Holstein cows. A 2-wk covariate and a 2-wk adaptation periods preceded a 10-wk experimental period used for data and sample collection. Treatments were: (1) basal diet supplemented with placebo (CON); and (2) basal diet supplemented with a blend of EO containing eugenol and geranyl acetate as main compounds. Supplementation with EO did not affect dry matter intake, milk and energy-corrected milk yields, and feed efficiency of cows, compared with CON. Milk fat and lactose concentrations were increased, and milk total solids (TS) concentration and milk fat yield tended to be increased by EO. Multiparous cows supplemented with EO tended to have slightly decreased dry matter and crude protein digestibility compared with CON multiparous cows. There was a tendency for increased ruminal pH by EO, whereas other rumen fermentation variables did not differ between treatments. Daily methane emission was not affected by EO supplementation, but methane emission intensity per kg of milk fat was decreased by 8.5% by EO. Methane emission intensity per kg of milk lactose and milk TS were decreased and methane emission intensity per kg of milk yield tended to be decreased by up to 10% in EO multiparous cows, but not in primiparous cows. The greenhouse gas-emitting potential of manure was not affected by EO supplementation. Compared with CON, fecal nitrogen excretion was increased by EO supplementation in multiparous, but not in primiparous cows, and milk nitrogen secretion (as a % of nitrogen intake) tended to be increased in EO supplemented cows. Blood variables were not affected by EO supplementation in the current study. Overall, dietary supplementation of EO did not affect lactational performance of the cows, although milk fat and lactose concentrations were increased. Most enteric methane emission metrics were not affected, but EO decreased methane intensity per kg of milk fat by 8.5%, compared with the control.

Effects of graded levels of dietary pomegranate peel on methane and nitrogen losses, and metabolic and health indicators in dairy cows

This study aimed to quantify the effects of dietary inclusion of tannin-rich pomegranate peel (PP) on intake, methane and nitrogen (N) losses, and metabolic and health indicators in dairy cows. Four multiparous, late-lactating Brown Swiss dairy cows (796 kg body weight; 29 kg/d of energy corrected milk yield) were randomly allocated to 3 treatments in a randomized cyclic change-over design with 3 periods, each comprising 14 d of adaptation, 7 d of milk, urine, and feces collection, and 2 d of methane measurements. Treatments were formulated using PP that replaced on a dry matter (DM) basis 0% (control), 5%, and 10% of the basal mixed ration (BMR) consisting of corn and grass silage, alfalfa, and concentrate. Gaseous exchange of the cows was determined in open-circuit respiration chambers. Blood samples were collected on d 15 of each period. Individual feed intake as well as feces and urine excretion were quantified, and representative samples were collected for analyses of nutrients and phenol composition. Milk was analyzed for concentrations of fat, protein, lactose, milk urea N, and fatty acids. Total phenols and antioxidant capacity in milk and plasma were determined. In serum, the concentrations of urea and bilirubin as well as the activities of alanine aminotransferase (ALT), aspartate aminotransferase, glutamate dehydrogenase, alkaline phosphatase, and γ-glutamyl transferase were measured. The data were subjected to ANOVA with the Mixed procedure of SAS, with treatment and period as fixed and animal as random effects. The PP and BMR contained 218 and 3.5 g of total extractable tannins per kg DM, respectively, and thereof 203 and 3.3 g of hydrolyzable tannins. Total DM intake, energy corrected milk, and methane emission (total, yield, and intensity) were not affected by PP supplementation. The proportions of C18:2n-6 and C18:3n-3 in milk increased linearly as the amount of PP was increased in the diet. Milk urea N, blood urea N, and urinary N excretion decreased linearly with the increase in dietary PP content. Total phenols and antioxidant capacity in milk and plasma were not affected by the inclusion of PP. The activity of ALT increased in a linear manner with the inclusion of PP. In conclusion, replacing up to 10% of BMR with PP improved milk fatty acid composition and alleviated metabolic and environmental N load. However, the elevated serum ALT activity indicates an onset of liver stress even at 5% PP, requiring the development of adaptation protocols for safe inclusion of PP in ruminant diets.

Innovative Thinking Drives Emissions Mitigation

_ The oil and gas industry walks a fine line between providing the energy supplies demanded by a growing global population and addressing the challenge of reducing greenhouse gas emissions, mainly methane. While the industry has made gains in many areas, critics have flagged concerns that the current pace of emissions mitigation needs to be faster and called for acceleration of the process. According to the International Energy Agency (IEA), methane is responsible for approximately 30% of the rise in global temperatures since the Industrial Revolution, making it the second-largest contributor to climate change behind carbon dioxide. Methane is released during oil and gas production processes, and the industry accounts for about a quarter of the global anthropogenic methane emitted into the atmosphere. With increasing recognition of their negative environmental impacts, these emissions are now under greater scrutiny by governments worldwide as they strive toward cleaner power generation sources. As a result, energy companies continue to find ways to effectively manage and reduce their methane emissions to remain compliant with new regulations. According to nonprofit organizations Clean Air Task Force and Ceres, industry efforts are delivering results. An analysis assessed the production-based emissions of more than 300 US producers, finding that the methane emissions intensity of natural gas production and the greenhouse-gas emissions intensity of oil and gas production vary dramatically across companies. The intensity of methane and greenhouse-gas emissions from the oil and gas sector declined 28% and 30%, respectively, between 2019 and 2021 among the largest producers in the country, the report said. However, according to the IEA, overall progress could have been faster. In a special report, the agency looked at the investment required to deliver a sharp reduction in emissions by 2030, finding that if the industry spent $75 billion—about 2% of its 2022 net income—to curb methane emissions through 2030, it would keep the sector on a pathway to achieve net-zero emissions by 2050. The agency also reported that methane abatement is one of the most cost-effective measures to cut emissions and would generate about $45 billion from the sale of captured methane (Fig. 1). Leak Detection Comparisons Promising advances in technology have improved methane measurement and leak detection. Traditionally a laborious and error-prone task, leak-detection technologies are undergoing a revolution. Drone technology, satellite surveillance, and infrared cameras are emerging as powerful tools in the industry’s arsenal to pinpoint leaks and fix them swiftly. Companies like Shell and BP have committed to routine checks via drones and cameras to spot leaks more accurately and promptly. By employing these technologies, the industry can reduce its environmental footprint and save valuable natural resources, transforming “waste” methane into a valuable energy source. ExxonMobil deployed new technology to expand measurement and mitigation of methane emissions and reduced methane emissions intensity from operated assets by more than 40% as of year-end 2021 vs. 2016 levels in line with greenhouse gas emission reduction plans. In its 2023 Advancing Climate Solutions Progress Report, the supermajor also said that it increased the amount it intends to invest through 2027 on lower-emission initiatives to approximately $17 billion, up by nearly 15%.

Unintended mitigation benefits of China's coal de-capacity policies on methane emissions

Coal de-capacity policies are often used to promote the integration of coal resources and optimize the production structure in China. This study used a bottom-up approach to evaluate the unintended effect of China's coal de-capacity policies on methane emissions mitigation from 2011 to 2019. Under the effect of such policies, the closed coal capacity was 46% of the total coal capacity in 2011. A total of 9567 coal mines with 1610 Mt of capacity were closed. The capacity of low CH4-content coal mines accounted for 77% in 2019, and the capacity of high and outburst CH4-content coal mines decreased by 9% compared to 2011. The adjustment in coal production structure in turn affects coal mine methane emission intensity, hence the national average coal mine emission factor decreased from 9 m3/t in 2011 to 8 m3/t in 2019. The coal de-capacity policies generated a cumulative 10.70 Tg of methane emissions mitigation from 2011 to 2019, even with rebounded coal production. As the number of coal mine closures continues to increase, the priority phase-out of high and outburst CH4-content mines will further lead to greater methane mitigation. In the future, more attention should be paid to methane emissions from abandoned mines.

Is it possible to predict the methane emission intensity of Swedish dairy cows from milk spectra?

Emissions of greenhouse gases (GHG), especially methane (CH4), from dairy production have received much research attention in the past 15 years, with the main focus being to identify factors affecting CH4 production and measures to reduce CH4 emissions from dairy cows. However, measurement of CH4 production by dairy cows in commercial herds is time-consuming and requires expensive equipment, so there is a need to find alternative ways to estimate individual and herd CH4 emissions. Regular milk analyses are performed for many cows, so data from mid-infrared spectroscopy (MIRS) on individual milk samples could perhaps be utilised to predict CH4 emissions intensity (MI, CH4 g/kg milk production). This study investigated the potential and limitations of predicting individual MI by integrating data from CH4 measurements made by an infrared sniffer (IRS) and milk MIRS data taken from fortnightly morning milkings during the full lactation records of 37 multiparous cows. Partial least square regression was used to create prediction models for six-week lactation sub-periods and for full lactations, which were validated using leave-one-cow-out cross-validation. Coefficient of determination in predicting MI was low, indicating that the method is not suitable for predicting variations in individual MI, although it should further be evaluated at herd level.

Factors Affecting Enteric Emission Methane and Predictive Models for Dairy Cows.

Enteric methane emission is the main source of greenhouse gas contribution from dairy cattle. Therefore, it is essential to evaluate drivers and develop more accurate predictive models for such emissions. In this study, we built a large and intercontinental experimental dataset to: (1) explain the effect of enteric methane emission yield (g methane/kg diet intake) and feed conversion (kg diet intake/kg milk yield) on enteric methane emission intensity (g methane/kg milk yield); (2) develop six models for predicting enteric methane emissions (g/cow/day) using animal, diet, and dry matter intake as inputs; and to (3) compare these 6 models with 43 models from the literature. Feed conversion contributed more to enteric methane emission (EME) intensity than EME yield. Increasing the milk yield reduced EME intensity, due more to feed conversion enhancement rather than EME yield. Our models predicted methane emissions better than most external models, with the exception of only two other models which had similar adequacy. Improved productivity of dairy cows reduces emission intensity by enhancing feed conversion. Improvement in feed conversion should be prioritized for reducing methane emissions in dairy cattle systems.

Nitrogen and energy losses and methane emissions from beef cattle fed diets with gradual replacement of maize silage and concentrate with grass silage and corn-cob mix.

Diets based on large proportions of grassland-based feed are uncommon in forage-based intensive beef production, thus contradicting governmental or commercial strategies to promote the use of grassland-based feed in ruminant production systems. Compared with typical maize silage/concentrate diets, grassland-based diets are associated with impaired nitrogen (N) and energy utilisation because of the comparably lower energy and higher CP content of these feeds. However, quantitative studies concerning the effects of increased dietary proportions of grassland-derived feeds on N and energy losses and utilisation and on methane emissions are missing and the compensation potential of using a limited proportion of an energy-rich forage is unknown. Therefore, we tested five diets with varying types and proportions of forage and concentrate. Three diets consisted of grass silage, maize silage, and concentrate in ratios of, g/kg DM, 100:600:300 (G100; control), 300:500:200 (G300), and 500:300:200 (G500), respectively. Two diets were composed of grass silage, corn-cob mix (CCM), and concentrate in ratios of, g/kg DM, 500:300:200 (G500CCM), and 750:150:100 (G750CCM), respectively. A high-protein concentrate (270g CP/kg DM) was fed to G100, whereas a low-protein concentrate (140g CP/kg DM) was used in the remaining diets. Diets were fed throughout the entire fattening period to groups of six Limousin-crossbred bulls each. When weighing 246±18kg, each animal underwent a 7-day total daily faeces and urine collection, which was followed by measuring methane emissions in respiration chambers for 48h. Total DM intake was similar across all diets, whereas the N intake varied (P<0.05). Urinary N loss (g/day) was the highest for G750CCM (28.2) and G100 (26.6) and lowest for G500CCM (15.2) and G300 (16.9) (P<0.001). Energy utilisation was comparable among all groups. Metabolisable energy intake decreased numerically only with increasing proportions of grass silage in the diet. Substituting maize silage with CCM counteracted the loss in metabolisable energy intake. Absolute methane emissions were not different across the groups, but methane emission intensity (mg/g body protein retention) varied (P<0.05), being numerically lower for G100 (349) and G500CCM (401) compared with the other groups (488 on average). In conclusion, the results show that the grass silage proportion in beef cattle diets can be substantially increased when strategically combined with energy-dense forages, such as CCM. This also limits the need for concentrate and additional protein sources; in addition, the associated urinary N emissions, which are potentially noxious to the environment, are avoided.

Effect of Metabolizable Protein Supply on Milk Performance, Ruminal Fermentation, Apparent Total-Tract Digestibility, Energy and Nitrogen Utilization, and Enteric Methane Production of Ayrshire and Holstein Cows

In North America, the nutrient requirements of dairy cattle are predicted using the Cornell Net Carbohydrate and Protein System (CNCPS) or the National Research Council (NRC). As Holstein is the most predominant dairy cattle breed, these models were developed based on the phenotypic, physiological, and genetic characteristics of this breed. However, these models may not be appropriate to predict the nutrient requirements of other breeds, such as Ayrshire, that are phenotypically and genetically different from Holstein. The objective of this study was to evaluate the effects of increasing the metabolizable protein (MP) supply using CNCPS on milk performance, ruminal fermentation, apparent total-tract digestibility, energy and N utilization, and enteric methane production in Ayrshire vs. Holstein lactating dairy cows. Eighteen (nine Ayrshire; nine Holstein) lactating cows were used in a replicated 3 × 3 Latin square design (35-d periods) and fed diets formulated to meet 85%, 100%, or 115% of MP daily requirement. Except for milk production, no breed × MP supply interaction was observed for the response variables. Dry matter intake (DMI) and the yields of energy-corrected milk (ECM), fat, and protein were less (p < 0.01) in Ayrshire vs. Holstein cows. However, feed efficiency and N use efficiency for milk production did not differ between the two breeds, averaging 1.75 kg ECM/kg DMI and 33.7 g milk N/100 g N intake, respectively. Methane yield and intensity and urinary N also did not differ between the two breeds, averaging 18.8 g CH4 /kg DMI, 10.8 g CH4 /kg ECM, and 27.6 g N/100 g N intake, respectively. Yields of ECM and milk protein increased (p ≤ 0.01) with increasing MP supply from 85% to 100% but no or small increases occurred when MP supply increased from 100 to 115%. Feed efficiency increased linearly with an increasing MP supply. Nitrogen use efficiency (g N milk/100g N intake) decreased linearly (by up to 5.4 percentage units, (p < 0.01) whereas urinary N excretion (g/d or g/100 g N intake) increased linearly (p < 0.01) with an increasing MP supply. Methane yield and emission intensity were not affected by MP supply. This study shows that feed efficiency, N use efficiency, CH4 (yield and intensity), and urinary N losses did not differ between Ayrshire and Holstein cows. Energy-corrected milk yield and feed efficiency increased, but N use efficiency decreased and urinary N losses increased with increasing dietary MP supply regardless of breed. Ayrshire and Holstein breeds responded similarly to increasing MP levels in the diet.

Empirical quantification of methane emission intensity from oil and gas producers in the Permian basin

Methane (CH4) emissions from the oil and natural gas (O&G) supply chain have been demonstrated to be one of the largest anthropogenic greenhouse gas emission sources ripe for mitigation to limit near-term climate warming. In recent years, exploration and production (E&P) operators have made public commitments to reducing their greenhouse gas emission intensity, yet little empirical information has been made available in the public domain to allow an accurate comparison of their emissions performance. In this study, we utilize a series of aircraft surveys of large CH4 point source emissions (∼101–104 kg CH4 hr−1) related to O&G production in the Permian Basin to enable comparison of company-level production-sector emission intensities. We calculate gas and total energy production normalized emission intensities for several of the largest E&P operators in the Permian Basin accounting for ∼85% of production within the flight region. We find differences of more than an order of magnitude in emission intensity across operators, with nearly half demonstrating a ⩾50% improvement in performance from 2019 to 2021. With the availability of such publicly attributed emissions data anticipated to increase in the future, we provide methodological insights and cautions to developing operator metrics from future empirical datasets.

Methane emissions and 13C composition from beef steers consuming binary C3-C4 diets.

Improvements in forage nutritive value can reduce methane emission intensity in grazing ruminants. This study was designed to evaluate how the legume rhizoma peanut (Arachis glabrata; RP) inclusion into bahiagrass (Paspalum notatum) hay diets would affect intake and CH4 production in beef steers. We also assessed the potential to estimate the proportion of RP contribution to CH4 emissions using δ13C from enteric CH4. Twenty-five Angus-crossbred steers were randomly allocated to one of five treatments (five steers per treatment blocked by bodyweight): 1) 100% bahiagrass hay (0%RP); 2) 25% RP hay + 75% bahiagrass hay (25%RP); 3) 50% RP hay + 50% bahiagrass hay (50%RP); 4) 75% RP hay + 25% bahiagrass hay (75%RP); 5) 100% RP hay (100%RP). The study was laid out using a randomized complete block design, and the statistical model included fixed effect of treatment, and random effect of block. Methane emissions were collected using sulfur hexafluoride (SF6) technique, and apparent total tract digestibility was estimated utilizing indigestible neutral detergent fiber as an internal marker. A two-pool mixing model was used to predict diet source utilizing CH4 δ13C. Inclusion of RP did not affect intake or CH4 production (P > 0.05). Methane production per animal averaged 250 g CH4/d and 33 g CH4/kg dry matter intake, across treatments. The CH4 δ13C were -55.5, -60.3, -63.25, -63.35, and -68.7 for 0%RP, 25%RP, 50%RP, 75%RP, and 100%RP, respectively, falling within the reported ranges for C3 or C4 forage diets. Moreover, there was a quadratic effect (P = 0.04) on the CH4 δ13C, becoming more depleted (e.g., more negative) as the diet proportion of RP hay increased, appearing to plateau at 75%RP. Regression between predicted and observed proportions of RP in bahiagrass hay diets based on δ13C from CH4 indicate δ13C to be useful (Adj. R2 = 0.89) for predicting the contribution of RP in C3-C4 binary diets. Data from this study indicate that, while CH4 production may not always be reduced with legume inclusion into C4 hay diets, the δ13C technique is indeed useful for tracking the effect of dietary sources on CH4 emissions.

Twinning in cattle: a pathway for reducing the methane intensity of beef

Context Reducing livestock emissions, the largest single contributor to agricultural emissions, is increasingly recognised as a high priority. The low biological efficiency of beef cattle, due to their long gestation period, long generational interval, and propensity to be uniparous, contributes to the high methane emissions intensity (kg CO2-e/kg product) of beef compared to most other food products. Aims We evaluate the potential of increasing the frequency of multiparous births (twinning) as a pathway to reducing the methane intensity of beef and the net methane emissions of intensive beef systems. Methods We simulate a uniparous herd structure and emissions profile using GrassGro™ livestock systems modelling software and then calculate the effects of an increasing frequency of multiparous births (twinning), up to 1.53 calves per cow joined, on methane emissions. Key results Our results demonstrate that beef from calves reared as twins has a 22% lower methane intensity than beef from a single reared calf. Although twinning reduces the methane intensity of beef, at the herd level, net methane emissions could rise by as much as 23% at 1.53 calves per cow joined if overall herd size is allowed to grow through an increased number of calves. If we decrease stocking rates, whilst also increasing twinning rates, it is possible to reduce net emissions by up to 14%, without changing productivity. Conclusions Our results illustrate the significant potential of twinning to decrease the methane intensity of beef and to increase the productivity per cow in intensive beef systems. Implications Despite this, twinning is unlikely to be a viable net emissions reduction pathway – as twinning will increase stocking rate unless herd structure is altered – unless a commercial or policy driver to reduce net methane emissions is established.

Can Intensified Pasture Systems Reduce Enteric Methane Emissions from Beef Cattle in the Atlantic Forest Biome?

The objective of this study was to evaluate the effect of different pasture systems on beef steers’ performance, dry matter intake, enteric methane emission, carcass production, forage quality, and animal production per hectare (ha). The trial was conducted at Embrapa Southeast Livestock, São Carlos/SP, Brazil. Sixty Cachim beef steers (5/8 Charolais × 3/8 Zebu) with initial liveweights of 255 ± 7 kg were evaluated for two years under five different grazing production systems (EXT = Extensive; INT = Intensive; iCL = Integrated crop livestock; iCLF = Integrated crop livestock forest; iLF = Integrated livestock forest). The final liveweight was greater (p &lt; 0.05) for the animals under the INT and iCL systems (484 ± 51 and 466 ± 79 kg, respectively) compared to animals in the iCLF, iLF and EXT systems (416 ± 57, 414 ± 50 and 429 ± 48 kg). The dry matter intake was significantly greater under the EXT system than it was under the iCL system (9.8 ± 2.1 and 7.5 ± 2.9 kg day−1). Regarding the emission intensity in relation to the liveweight gain per unit area (g CH4 kg LWG−1 ha−1 year−1), it differed significantly among the systems (EXT = 1.6; INT = 0.6; iCL = 0.8; ICLF = 1.1; ILF = 0.7). Similarly, the methane emission intensity differed in relation to the carcass production (kg CH4 kg−1 carcass; EXT = 0.496; INT = 0.250; iCL = 0.297; iCLF = 0.345; iLF = 0.286). Beef cattle that are raised in intensive and/or integrated pasture systems have a greater availability of forage mass and nutrients than those that are raised extensively. Pasture systems that undergo soil pH correction and fertilization, rotational grazing and/or integrated with maize cropping produce animals with greater average daily gain and final liveweights, thereby lessening the enteric methane emissions per kg of weight gain. In these systems, the efficiency in terms of the gain per land area is also greater, however, the systems that are integrated with a forest component (iLF and iCLF) are equal to that of the EXT system. The same pattern is observed in the intensity of the methane emission as for the efficiency of the animal gain per unit of land area.

N-fertilization of tropical pastures improves performance but not methane emission of Nellore growing bulls.

Grazing management and N-fertilizer have been reported to improve tropical forage productivity and quality, however, their effect on methane emission of grazing animals remains uncertain. Therefore, this study aimed to assess the effects of increasing application rates of nitrogen (N) fertilization of Marandu palisadegrass under continuous stocking on intake, digestibility, nitrogen balance, and enteric methane emissions of Nellore growing bulls. We hypothesized that changes in the forage nutritive value caused by N fertilization of pastures combined with adequate grazing management (e.g., greater crude protein [CP] and digestibility) would lead to an increase in animal productivity (e.g., greater average daily gain [ADG] and gain per area), and then, to a decrease in methane emission intensity. Treatments consisted of different annual application rates of nitrogen fertilization: 0, 75, and 150 kg N/ha using ammonium nitrate (32% N) as the nitrogen source. The experimental design was completely randomized, with three treatments and four replications (12 paddocks). Intake, digestibility, N balance, and methane emissions were measured in eight animals per treatment. CP intake, digestibility and N balance increased linearly with the increase in N fertilization (P < 0.05). In addition, stocking rate (SR) and ADG linearly increased from 1.75 animal unit (AU = 450 kg)/ha and 0.62 kg/d (0 kg N/ha) to 3.75 AU/ha and 0.82 kg/d (150 kg N/ha), respectively. Individual methane emissions nor methane emission intensity were affected by treatment with an average of 164.7 g/d and 199.7 g/kg ADG (P > 0.05). Annual N fertilization with ammonium nitrate between 75 and 150 kg N/ha in palisadegrass pastures under continuous stocking enhances animal performance per unit area yet not affecting neither methane production nor intensity.

Effects of early herbage cutting and vine leaves on methane emission, urine nitrogen losses, and the milk fatty acid profile of dairy cows.

Methane mitigation in dairy cows is an essential part of combating global warming. Governments and consumers have become increasingly interested in herbage-based feeding, and premium prices are often paid for these types of dairy products. However, this feeding strategy is presumed to produce more methane per unit of feed or milk than corn silage- or concentrate-based diets due to higher fiber intakes. Immature herbage is preferred to maintain dairy cow performance, but the high content of N and digestible fiber may increase methane and urine N emissions compared with more mature herbage. Tannin-containing feeds, such as vine leaves (Vitis vinifera), may help to combat the emissions associated with feeding immature herbage. Our study aimed to evaluate differences between early-stage (ES; 21 d of regrowth) versus late-stage (LS; 42 d) herbage and the effects of vine leaves on methane and nitrogenous emissions and the milk fatty acid profile of dairy cows. Twenty-four mid- to late-lactating dairy cows were randomized to 4 dietary groups (n = 6) in a factorial study design. Each of the 4 diets contained 69% fresh mixed legume-grass herbage, 13% grass hay, and 5% concentrate on a dry matter (DM) basis. Two diets were based on immature fresh mixed legume-grass herbage and grass hay (ES), and 2 contained more mature fresh mixed legume-grass herbage and grass hay (LS). Of these, 1 contained 13% vine leaves (VL+) and the other an additional 13% hay (VL-). No significant differences were observed in DM intake or milk yield across the diets. Methane emission intensity was lowest with ES-VL+ diets compared with LS-VL- diets (-30%; 17.1 vs. 24.5 mg/kg of energy-corrected milk). Methane yield decreased by 17% and 20% when related to the intake of DM and digested organic matter for ES-VL+ compared with LS-VL- diets (16.9 vs. 20.3 g/kg of DM intake; 23.5 vs. 29.3 g/kg of digestible organic matter). Immature grass and vine leaf addition each caused about half of the respective declines. Cows consuming any of the ES diets and the LS-VL+ diet consumed and excreted (urinary N) significantly more N than those consuming LS diets. However, when related to N intake, no differences were recorded. Unexpectedly, vine leaves did not mitigate urine N excretion; however, they lowered the n-6:n-3 ratio and increased concentrations of vaccenic and rumenic acids in both ES and LS diets. Our results demonstrate that feeding immature herbage in combination with vine leaves reduces methane yield; however, the associated high urinary N losses need to be addressed.

Effects of replacing Brachiaria hay with either Desmodium intortum or dairy concentrate on animal performance and enteric methane emissions of low-yielding dairy cows

In Africa, cattle are often fed low quality tropical roughages resulting in low-yielding animals with high methane (CH4) emission intensity (EI, g CH4/per unit of product). Supplementation with protein is known to improve the nutritive value of the otherwise low-quality diets. However, animal nutrition studies in East Africa that are accompanied by CH4 emission measurements are lacking. Thus, an animal experiment was conducted to quantify the effect of supplementing cattle fed mainly on low-quality Urochloa brizantha hay (control diet; CON; crude protein (CP) = 7.4%) or supplemented with either a tannin-rich leguminous fodder, Desmodium intortum hay (DES) or a commercial dairy concentrate (CUBES) on voluntary dry matter intake (DMI), nutrient apparent total tract digestibility, nitrogen (N) retention, enteric CH4 production and animal performance (milk and average daily gain). Twelve mid-lactating crossbred (Friesian × Boran) cows (initial liveweight = 335 kg) were used in a 3×3 (Period × Diet) Latin square design with each period running for four weeks. Compared to CON, DES decreased nutrient (DM, OM, CP) intake, apparent total tract digestibility and daily milk yield. In contrast, CUBES increased nutrient intake and animal performance compared to CON, while nutrients’ apparent total tract digestibility was not different, except for CP digestibility that increased. Compared to CON, DES and CUBES improved overall N retention by the animals as a proportion of N intake. The DES diet compared with CON and CUBES, shifted the proportion of N excretion via urine to the fecal route, likely because of its tannin content. Both DES and CUBES, compared to CON, reduced methane yield (MY, g CH4/kg DMI) by 15% and 9%, respectively. The DES diet reduced absolute enteric CH4 emissions by 26% while CUBES increased emissions by 11% compared to CON. Based on the present findings, high supplementation levels (&amp;gt;50%) of Desmodium intortum hay is not recommended especially when the basal diet is low in CP content. Supplementation with lower levels of better managed Desmodium intortum forage however, need to be investigated to establish optimal inclusion levels that will improve animal productivity and reduce environmental impact of livestock in smallholder tropical contexts.