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The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Inhibition of methyl-coenzyme M reductase can suppress the activity of ruminal methanogens, thereby reducing enteric methane emissions of ruminants. However, developing specific and environmentally friendly inhibitors is a challenging endeavor. To identify a natural and effective methane inhibitor that specifically targets methyl-coenzyme M reductase, molecular docking technology was employed to screen a library of phytogenic compounds. A total of 52 candidate compounds were obtained through molecular docking technique. Rosmarinic acid (RA) was one of the compounds that could traverse a narrow channel and bind to the active sites of methyl-coenzyme M reductase, with a calculated binding free energy of −9.355 kcal/mol. Furthermore, the effects of RA supplementation on methane production, rumen fermentation, and the microorganism community in dairy cows were investigated through in vitro rumen fermentation simulations according to a random design. Supplementation of RA resulted in a 15% decrease in methane production compared with the control. In addition, RA increased the molar proportion of acetate and propionate, whereas the sum of acetate and butyrate divided by propionate was decreased. At the bacterial level, the relative abundance of Rikenellaceae RC9 gut group, Christensenellaceae R7 group, Candidatus Saccharimonas , Desulfovibrio , and Lachnospiraceae FE2018 group decreased with RA supplementation. Conversely, the addition of RA significantly increased the relative abundance of DNF00809 (a genus from Eggerthellaceae), Denitrobacterium , an unclassified genus from Eggerthellaceae , an unclassified genus from Bacteroidales , and an unclassified genus from Atopobiaceae. At the archaeal level, the relative abundance of Methanobrevibacter decreased, whereas that of Methanosphaera increased with RA supplementation. These findings suggested that RA has the potential to be used as a novel natural additive for inhibiting ruminal methane production. [ABSTRACT FROM AUTHOR]

• A high cooling capacity Stirling cryocooler is developed to liquefy boil-off gas. • The relative Carnot efficiency of the cryocooler reaches 33.28% at 77 K. • The cryocooler is installed in the skid-mounted BOG liquefaction system. • The system produces 27.3 L/h LNG and shows a great application potential. Natural gas is a cost-effective energy supply for the development of low-carbon economy and environmental protection worldwide. Despite the environmentally friendly properties of natural gas, methane is a potent greenhouse gas. Therefore, efficiently recovering the boil-off methane gas (BOG) generated from liquefied natural gas (LNG) devices is becoming a pressing problem involving both the economy and the environment. The Stirling cryocooler is a promising technology in dealing with BOG. This technology has superior characteristics, including large cooling capacity, high efficiency, compact configuration, and flexible operating characteristics. In the study, a high cooling capacity Stirling cryocooler was developed. The influences of the regenerator on the cryocooler were studied. The refrigeration performance and the operating characteristics were systematically analyzed. A cooling power of 1050 W at 77 K with a relative Carnot efficiency of 33.28 % was achieved. Accordingly, the cryocooler outperforms the reported Stirling-type cryocoolers in terms of overall performance. A BOG liquefaction system based on the cryocooler was installed in an LNG refueling station. On-site test results demonstrated that the system can produce 27.3 L/h LNG with a power consumption of 14.5 kW. The present research lays a good foundation for future optimizations and applications of the cryocooler in liquefying BOG. [ABSTRACT FROM AUTHOR]

Reduction of methane emission may become necessary for sustainable milk production. Several studies indicate a relationship between rumination time and the level of methane emission. The objectives of the current study were to estimate environmental factors affecting daily rumination time in high-yielding dairy cattle, genetic parameters for rumination time across parities, and environmental and genetic correlations between rumination time and economic traits, and to predict the consequence of inclusion of this trait in the Israeli breeding index. The data included more than 30 million daily records from 77,697 Israeli Holstein cows for rumination time and milk production. A lactation measure of daily rumination time per cow was computed as the mean of the residuals from a linear model analysis with rumination time as the dependent variable. The independent variables were parity and the square root, linear, quadradic and inverse of DIM by parity. Because of the shape of the lactation curve for rumination time, separate linear model analyses were performed for records up to 40 DIM and records with >40 DIM. The phenotypic correlation between first- and second-parity lactations for rumination time was almost 0.8, and close to 0.7 for milk. The heritability of lactation rumination time was close to 0.44 for parities 1 to 3. Heritability for milk production decreased from 0.5 in first parity to 0.3 in third parity. For both traits, genetic correlations among parities were all >0.9. Thus, for routine genetic analysis of rumination time, records in the different parities can be considered the same trait. The genetic correlation between rumination time and milk on first parity was 0.25 and increased slightly with increase in parity. Genetic correlations between rumination time, based on the first 40 DIM, were economically unfavorable with retained placenta but economically favorable with metritis, ketosis, and displaced abomasum. Genetic correlations between rumination time and the 9 traits included in the Israeli breeding index (milk, fat, and protein production; SCS; female fertility; herd-life; milk production persistency; calving ease; and calf mortality) were all economically favorable, except for the correlation of 0.17 with SCS. With the current index, daily rumination time with a current mean of 536 min and SD of 90 min is expected to increase by 11 min/d after 10 yr of selection. Inclusion of this trait with a positive index weight equivalent to 10% of the index should increase rumination time by 19 min. All changes in expected gains due to inclusion of rumination time in the index were economically positive, except for fat and SCS. Inclusion of rumination time in the index should result in 1 kg less gain in fat, a miniscule gain of 0.03 for SCS; and gains of 1.5 kg protein, 0.3% female fertility, and 5 d herd-life. Even though the case for a genetic correlation between rumination time and methane emission is still weak, inclusion of this trait in the commercial index may be justified, considering that equipment is now commercially available for routine recording at reasonable cost. [ABSTRACT FROM AUTHOR]

• Accounting methods of agricultural methane are summarized. • Influencing factors of emission sources from agricultural sources were analyzed. • Mitigation strategies based on accounting and actual situation are proposed. Methane is one of the major greenhouse gases (GHGs) and agriculture is recognized as its primary emitter. Methane accounting is a prerequisite for developing effective agriculture mitigation strategies. In this review, methane accounting methods and research status for various agricultural emission source including rice fields, animal enteric fermentation and livestock and poultry manure management were overview, and the influencing factors of each emission source were analyzed and discussed. At the same time, it analyzes the different research efforts involving agricultural methane accounting and makes recommendations based on the actual situation. Finally, mitigation strategies based on accounting results and actual situation are proposed. This review aims to provide basic data and reference for agriculture-oriented countries and regions to actively participate in climate action and carry out effective methane emission mitigation. [Display omitted] [ABSTRACT FROM AUTHOR]

Anthropogenic methane emissions are a leading cause of the increase in global average temperatures, often referred to as global warming. Flooded soils play a significant role in methane production, where the anaerobic conditions promote the production of methane by methanogenic microorganisms. Rice fields contribute a considerable portion of agricultural methane emissions, as rice plants provide both factors that enhance and limit methane production. Rice plants harbor both methane- producing and methane-oxidizing microorganisms. Exudates from rice roots provide source for methane production, while oxygen delivered from the root aerenchyma enhances methane oxidation. Studies have shown that the diversity of these microorganisms depends on rice cultivars with some genes characterized as harboring specific groups of microorganisms related to methane emissions. However, there is still a need for research to determine the balance between methane production and oxidation, as rice plants possess the ability to regulate net methane production. Various agronomical practices, such as fertilizer and water management, have been employed to mitigate methane emissions. Nevertheless, studies correlating agronomic and chemical management of methane with productivity are limited. Moreover, evidences for breeding low-methane-emitting rice varieties are scattered largely due to the absence of coordinated breeding programs. Research has indicated that phenotypic characteristics, such as root biomass, shoot architecture, and aerenchyma, are highly correlated with methane emissions. This review discusses available studies that involve the correlation between plant characteristics and methane emissions. It emphasizes the necessity and importance of breeding low-methane-emitting rice varieties in addition to existing agronomic, biological, and chemical practices. The review also delves into the ideal phenotypic and physiological characteristics of low-methane-emitting rice and potential breeding techniques, drawing from studies conducted with diverse varieties, mutants, and transgenic plants. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate trade-offs between enteric and manure CH 4 emissions, and the size of synergistic effects for CH 4 and nitrogenous emissions (NH 3 and N 2 O). Sixty-four Holstein-Friesian cows were blocked in groups of 4 based on parity, lactation stage, and milk yield. Cows within a block were randomly allocated to a dietary sequence in a crossover design with a grass silage-based diet (GS) and a corn silage-based diet (CS). The GS diet consisted of 50% grass silage and 50% concentrate, and CS consisted of 10% grass silage, 40% corn silage, and 50% concentrate (dry matter basis). The composition of the concentrate was identical for both diets. Cows were housed in groups of 16 animals, in 4 mechanically ventilated barn units for independent emission measurement. Treatment periods were composed of a 2-wk adaptation period followed by a 5-wk measurement period, 1 wk of which was without cows to allow separation of enteric and manure emissions. In each barn unit, ventilation rates and concentrations of CH 4 , CO 2 , NH 3 , and N 2 O in incoming and outgoing air were measured. Cow excretion of organic matter was higher for CS compared with GS. Enteric CH 4 and cow-associated NH 3 and N 2 O emissions (i.e., manure emissions excluded) were lower for CS compared with GS (−11, −40, and −45%, respectively). The CH 4 and N 2 O emissions from stored manure (i.e., in absence of cows) were not affected by diet, whereas that of NH 3 emission tended to be lower for CS compared with GS. In conclusion, there was no trade-off between enteric and manure CH 4 emissions, and there were synergistic effects for CH 4 and nitrogenous emissions when grass silage was exchanged for corn silage, without balancing the diets for crude protein content, in this short-term study. [ABSTRACT FROM AUTHOR]

Livestock production systems with ruminants play a relevant role in the emission of the greenhouse gas CH 4 , which is known to significantly contribute to global warming. Consequently, it is a major societal concern to develop strategies in mitigating such emissions. In addition to breeding toward low-emitting cows, management strategies could also help in reducing greenhouse gas emissions from dairy farms. However, information is required for appropriate decision making. To the best of our knowledge, this is the first study that considers different, already available equations to estimate CH 4 emissions of small-scale dairy farms in the mountain region, which largely differ from large dairy farms in the lowlands concerning management and production. For this study, 2 different production systems, both typical for small-scale dairy farming in mountain regions, were simultaneously run over 3 yr at an experimental farm as follows: (1) a high-input production system, characterized by intensive feeding with high amounts of external concentrates and maize silage, year-round housing, and high yielding Simmental cattle breed, and (2) a low-input production system, characterized by prevailing hay and pasture feeding and silage ban, thus covering most of the energy requirements by forage harvested on-farm and the use of the local Tyrolean Grey cattle breed. Results reveal that feeding management has a significant effect on the amount of CH 4 emissions. The low-input production system produced less CH 4 per cow and per day compared with the high-input production system. However, if calculated per kilogram of milk, the high-input scenario produced proportionally less CH 4 than the low-input one. Findings of this study highlight the potential to assess in a fast and cost-effective way the CH 4 emission in different dairy production systems. This information contributes to the debate about the future of sustainable milk production in mountain regions, where the production of feed resources is climatically constrained, and could be useful for breeding purposes toward lower CH 4 -emissions. [ABSTRACT FROM AUTHOR]

This study consists of milk fatty acid (FA) data collected during 2 in vivo experiments. For this study, 8 cows from each experiment were included in a replicated 4 × 4 Latin square design. At the start of experiment 1 (Exp1) cows were at (mean ± standard deviation) 87 ± 34.6 d in milk, 625 ± 85.0 kg of body weight, and 32.1 ± 4.17 kg/d milk yield and at the start of experiment 2 (Exp2) cows were at 74 ± 18.2 d in milk, 629 ± 87.0 kg of body weight, and 37.0 ± 3.2 kg/d milk yield. In Exp1, we examined the effects of gradual replacement of barley with hulled oats (oats with hulls) on milk FA composition. The basal diet was grass silage and rapeseed meal (58 and 10% of diet DM, respectively), and the 4 grain supplements were formulated so that barley was gradually replaced by hulled oats at levels of 0, 33, 67, and 100% on dry matter basis. In Exp2, we examined (1) the effects of replacing barley with both hulled and dehulled oats (oats without hulls) and (2) the effects of gradual replacement of hulled oats with dehulled oats on milk FA composition. The basal diet was grass silage and rapeseed meal (60 and 10% of diet DM, respectively), and the 4 pelleted experimental concentrates were barley, hulled oats, a 50:50 mixture of hulled and dehulled oats, and dehulled oats on dry matter basis. In Exp1, gradual replacement of barley with hulled oats decreased relative proportions of 14:0, 16:0, and total saturated FA (SFA) in milk fat linearly, whereas proportions of 18:0, 18:1, total monounsaturated FA, and total cis unsaturated FA increased linearly. Transfer efficiency of total C18 decreased linearly when barley was replaced by hulled oats in Exp1. In Exp2, relative proportions of 14:0, 16:0, and total SFA were lower, whereas proportions of 18:0, 18:1, monounsaturated FA, and cis unsaturated FA were higher in milk from cows fed the oat diets than in milk from cows fed the barley diet. Moreover, in Exp2, gradual replacement of hulled oats with dehulled oats slightly decreased the relative proportion of 14:0 in milk fat but did not affect the proportions of 16:0, 18:0, 18:1, total SFA, monounsaturated FA, trans FA, or polyunsaturated FA. In Exp2, transfer efficiency of total C18 was lower when cows were fed the oat diets than when fed the barley diet and decreased linearly when hulled oats were replaced with dehulled oats. Predictions of daily CH 4 emissions (g/d) using the on-farm available variables energy-corrected milk yield and body weight were not markedly improved by including milk concentrations of individual milk FA in prediction equations. In conclusion, replacement of barley with oats as a concentrate supplement for dairy cows fed a grass silage-based diet could offer a practical strategy to change the FA composition of milk to be more in accordance with international dietary guidelines regarding consumption of SFA. [ABSTRACT FROM AUTHOR]

• A pipeline for the stepwise processing of raw data from methane emission sniffers, including instrument monitoring, time synchronization, linking with animal IDs, background concentration estimation, and operation with data on daily and weekly methane records from dairy cows was developed and validated. • Objective criteria for the selection of valid data were established. • The obtained concentration phenotypes were found to be moderate to highly repeatable. "Sniffers" record methane (CH 4) emissions from cows visiting milking robots, providing gas concentration data. These instruments have infrared carbon dioxide (CO 2) and CH 4 sensors, an air pump, and a data logger. In this study, a process for the synchronization of sniffer emissions data with cow identification (ID) data and records from automatic milking systems (AMSs) was developed. The process enables the extraction of gas phenotypes for genetic analysis. It involves the calculation of intermediate control variables to account for time drift in data loggers, sensor calibration drift, and background concentration fluctuations, and the condensation of data from each milking visit into a single datapoint. The process was developed and assessed with research station data from three groups of approximately 70 cows, each accessing one AMS unit over a 2-month period. Raw emissions data, including clock times, from CH 4 and CO 2 channels were recorded every second. They were synchronized with the AMS data using specific events occurring in the CH 4 or CO 2 channel at the beginning or end of each milking event. The synchronized data were divided into non-milking (baseline, ambient gas concentrations) and cow ID–linked milking (cow emissions) sets. The non-milking periods varied in duration from a few seconds to hours, and some were interrupted by unrecorded events. Baseline values were extracted after the filtering of non-milking period data against unrecorded events (e.g., washing, feed-only sessions) and the use of a small fractile as the baseline estimate. At the beginning of each milking event, 30–45 s were required for the CH 4 and CO 2 concentrations to reach stable high levels, and most events lasted at least 5 min. Accordingly, a restricted recording window of 30–300 s, which excluded the initial unstable period while retaining data from the majority of milking events, was established. Gas concentrations significantly exceeding the baseline were selected as responses to ensure that only data obtained when the cows' heads were sufficiently close to the sniffer air inlets were included. The mean value of the selected records was used as the response phenotype for each milking event. The concentration phenotypes showed moderate to high repeatability, but the CH 4 :CO 2 ratio had only moderate repeatability. The pipeline developed in this study enables the effective extraction of baseline-adjusted emissions phenotypes from sniffer data obtained in milking robots. [ABSTRACT FROM AUTHOR]

With the deterioration of global climate and environment, the carbon emission of the oil and gas industry has been an important issue of global concern. At present, there is a lack of systematic research on carbon emission calculation of natural gas pipeline from construction to disposal. We propose a life cycle assessment method for natural gas pipeline in order to quantify the carbon emissions from construction to disposal. The carbon emissions of natural gas pipeline are divided into four parts in this model: manufacturing, construction, operation, and recycling. For each of the four stages, carbon emissions from material production and construction, facility construction and equipment operation are all detailedly calculated. In addition, methane, the main component of natural gas, has a non-negligible impact on the atmosphere. Therefore, gas leakage from the pipeline system is also considered in this paper. And data from actual pipelines are utilized in the case study. The results show that the carbon emissions of these pipelines are in the range of 26.58–67.14 t CO 2 / (km×108 m3 / a) and 11.41–30.27 t CH 4 / (km×108 m3 / a). Among them, the production process of pipelines contributes the most to carbon emissions, accounting for about 80 % of the total CO 2 emissions. Through sensitivity analysis, we found that pipeline parameter, power emission factor, and compressor operation status turn out to be the main factors affecting carbon emission. With the establishment of this model, potential carbon emission of planned pipelines can be estimated, which has guiding significance for future pipeline construction. • Conduct a comprehensive life cycle inventory analysis on natural gas pipeline system. • Analyze potential CO 2 emission and methane emission in natural gas pipeline system. • Summarize the key parameters affecting the system's total emissions and their sensitivity. • Propose a fitting formula to estimate pipeline emission based on real data. [ABSTRACT FROM AUTHOR]

• The combination of Sentinel-5P and Sentinel-2 observation identifies and monitor CH 4 leakage in the oil/gas field. • Sentinel-5P data to find CH 4 anomalies and Sentinel-2 to zoom in on this location to find CH 4 plumes. • Band-11 and band-12 of Sentinel-2 can be utilized for identifying CH 4 plumes. • The MBMP method can produce a clearer plume than the SBMP and MBSP methods. Methane (CH 4) ranks as the second most abundant greenhouse gas globally, following carbon dioxide (CO 2), constituting approximately one-sixth of total greenhouse gas emissions. While CH 4 levels in the atmosphere are lower compared to CO 2 , the warming potential of CH 4 greatly surpasses that of CO 2. With a relatively short atmospheric lifespan of approximately 12 years, mitigating CH 4 emissions presents a viable means to alleviate the impacts of climate change on human populations within a concise timeframe. The atmospheric sources of CH 4 primarily stem from two categories: natural and anthropogenic. A small number of super-emitters frequently contribute significantly to the overall regional emissions. Monitoring and repairing leaks from super emitters of CH 4 is a low-cost and effective way to slow down the greenhouse effect. Remote sensing satellites have gradually become an effective means of monitoring CH 4 leakage due to their low cost and large coverage. There is a range of satellites that can be used to monitor CH 4 concentrations and emissions, such as Sentinel-5P, GOSAT, GHGSat, Sentinel-2, GaoFen-5, Landsat, and so on. Because the pixel resolution is rough (about 7 km), Sentinel-5P (S5P) can only identify high-value CH 4 anomalies in some areas, making it difficult to identify and monitor point source CH 4 emission plumes. Sentinel-2(S2) can accurately detect CH 4 leakage in band-11 and band-12 with high pixel resolution (about 20 m) but with every 5-day revisit time. In this paper, we monitored and quantified oil and gas field CH 4 leakage using a combination of S5P and S2 data by taking advantage of the high temporal resolution (daily) of S5P and high spatial resolution (20 m) of S2. We used S5P data to find CH 4 anomalies. Then we used S2 to zoom in on this location to find CH 4 plumes. We used three different methods: Single-band–multi-pass (SBMP), Multi-band–single-pass (MBSP), and Multi-band-multi-pass (MBMP) to identify CH 4 plumes. Using these methods, we successfully monitored three emission source cases (Algeria, Mexico, and Turkmenistan) and discussed them. Through the above three cases, we can conclude that the MBMP method has higher stability in identifying S2 CH 4 plumes. [ABSTRACT FROM AUTHOR]

To mitigate the high greenhouse effect caused by methane emissions of natural gas engines, this study employed the citric acid complexation method to synthesize Ce/Ti-doped LaMnO 3 perovskite catalysts. Firstly, the properties of perovskite catalysts were investigated through several characterization techniques and activity evaluations. Secondly, density functional theory (DFT) calculations were performed to study the effects of Ce/Ti doping on perovskite unit cell properties and methane adsorption characteristics. Results indicate that Ce/Ti doping is conducive to enhancing the magnetic properties and attractive forces between particles, thereby improving the crystallinity and specific surface area of catalyst. Additionally, it enhances the oxygen migration rate, promotes the formation of low-temperature reduction active components and reduces the reduction temperature for the catalysts. When Ce/Ti are co-doped, the ratios of the surface-active elements Mn4+/Mn3+ and O−/O2− on the catalyst reach their maximum values of 1.56 and 1.53, respectively. The co-doping also leads to the formation of alkaline sites such as Mn-O and Ti-O metal pairs, which facilitate the dehydrogenation oxidation of methane. Ce/Ti-co-doped LaMnO 3 perovskite exhibits the optimal low-temperature oxidation activity towards methane, with an ignition temperature reduced to 269 °C and complete methane conversion at 479 °C. Ce/Ti doping enhances the adsorption behavior of methane on catalyst surface, with the adsorption energy of −5.4361eV. Meanwhile, Ce/Ti doping results in a significant transfer of electrons from H 1 atoms of methane to Mn atoms and increases the charge directivity of the surface-active atoms of catalysts, and in turn, it leads to higher catalytic performance and structural stability. • Ce/Ti doping increases the crystallinity and specific surface area of the catalysts. • Ce/Ti doping will improve the low-temperature reducibility of perovskite catalysts. • The formation of Ti-O alkaline sites facilitates the catalytic oxidation of methane. • Ce/Ti-co-doped LaMnO 3 perovskite exhibits optimal oxidation activity to methane. • Ce/Ti co-doping enhances adsorption of methane and structural stability of catalyst. [ABSTRACT FROM AUTHOR]

A potent greenhouse gas, methane, contributes to global warming, primarily from livestock activities such as fermentation and manure management. Recognized as a low-carbon agricultural approach, coupled crop–livestock systems are gaining increasing attention for mitigating methane emissions and environmental impacts. This study focused on Inner Mongolia to estimate its methane reduction potential. We calculated methane emissions using a combination of bottom-up and top-down methods, analyzed livestock distribution, estimated manure production, and assessed the potential of manure to replace chemical fertilizers based on crop nutrient demand. Livestock emissions totaled approximately 769.0 kt. Adopting crop–livestock coupling could reduce emissions by 30.1 kt. Returning manure as fertilizer can cover 57.7% of cropland, saving 57% nitrogen and 20% phosphorus fertilizers, thus reducing costs by $296.3 million. The study has provided a scientific reference for developing methane emission reduction strategies, which can shed light on tackling climate change in the context of agricultural systems. [Display omitted] • Bottom-up and top-down methods were combined for precise CH 4 emission assessment. • Strategies to reduce CH 4 emissions require spatially explicit analysis. • Manure to fertilizer cuts CH 4 by 30.1 kt, covering 57.7% cropland in Inner Mongolia. • Crop-livestock coupling yields synergies (cuts carbon, boosts environment & economy). [ABSTRACT FROM AUTHOR]

Returning straw directly to the field soil is an important strategy that is widely advocated for the disposal of cereal straw. Straw carbonization to form biochar is an innovative approach for treating straw, and its incorporation into the soil is beneficial for improving soil quality. To assess the long-term impacts of these two technologies on greenhouse gas (GHG) emissions and crop yields, a decade-long field study, comparing three treatments, namely direct incorporation of straw from the crop into the field (SCF), incorporation of biochar from straw into the field (BCF), both combined with chemical fertilizer, and the incorporation of chemical fertilizer alone into the field (CF), was conducted on a rice-wheat rotation system in eastern China. Results showed that SCF and BCF achieved the same rice yield as CF treatment alone, while BCF caused a slight decrease in wheat yield. However, there was no significant difference in wheat yield between SCF and BCF, with no significant 'season × treatment' interactions observed. Over the ten-year observation period, rice yields were found to be greatly influenced by air temperature and precipitation, whereas wheat yields were more dependent on precipitation. In terms of GHG emissions, SCF increased annual methane (CH 4) emissions by 144 % but reduced annual nitrous oxide (N 2 O) emissions by 40 %, resulting in an 80 % increase in annual global warming potential (GWP) compared with CF. On the other hand, BCF reduced CH 4 and N 2 O emissions by 58 % and 25 %, respectively, relative to SCF, in the rice season. Despite slightly higher N 2 O emissions in the wheat season, BCF reduced the annual GWP by 51 %, relative to SCF. Additionally, the relative CH 4 emissions of SCF/CF and BCF/CF decreased over time, with BCF showing lower CH 4 emissions than CF after five years. Overall, the findings suggest that straw carbonization into biochar before soil incorporation could be a promising approach to mitigating GHG emissions and maintaining crop yields compared with incorporating straw directly into the soil in the rice-based rice-wheat rotation systems. • SCF and BCF achieved the same rice yield as CF treatment alone. • There was no significant difference in wheat yield between SCF and BCF. • SCF increased annual GWP by 80 % compared with CF. • BCF decreased annual GWP by 12 % relative to CF and by 51 % compared with SCF. • SCF/CF and BCF/CF ratio in CH 4 emissions decreased over the ten years. [ABSTRACT FROM AUTHOR]

Straw incorporation improves soil fertility but also poses environmental challenges due to increasing methane (CH 4) emissions in paddy fields. Whether nitrogen (N) and water management can balance rice yield and CH 4 emissions under different crop straw incorporation is still not well-documented. A three-year field experiment was conducted to probe the comprehensive effects of N application ratios and irrigation regimes on rice yield, rhizosphere soil properties, and CH 4 emissions, along with the underlying mechanisms of CH 4 emission variations among different straw types. A two-factor randomized block design was used with two Japonica rice cultivars as materials in 2020 and 2021. The straw incorporation treatment included no straw incorporation (NS), wheat straw incorporation (WS), and rape straw incorporation (RS). The N fertilizer application treatments included local farmers' fertilizer practice (LFP) and increasing basal fertilizer rate (IBF). Two irrigation practices, continuously-flooded irrigation (CF) and alternate wetting and drying irrigation (AWD), were designed under the WS and RS treatments in 2022. 1) WS-IBF and RS-IBF enhanced yield by 6.70∼9.03 % and 8.13∼9.50 % compared to WS-LFP and RS-LFP, respectively. AWD further increased yield by 6.28∼7.76 % compared to CF. 2) WS-IBF and RS-IBF enhanced dissolved organic carbon (DOC) content, synchronously boosted the methanogens (mcrA) and methanotrophs (pmoA) abundances, but decreased the pmoA/mcrA ratio, which significantly promoted CH 4 emission flux in early growth stage. This resulted in a 5.04∼8.01 % and 4.60∼7.88 % increase in CH 4 emissions compared to WS-LFP and RS-LFP, respectively, but a decrease in yield-scaled CH 4 emissions. AWD reduced DOC content, facilitated the conversion of ammonium N to nitrate N, increased dissolved oxygen content, and hence decreased CH 4 emissions by 23.41∼24.38 % compared to CF. 3) RS significantly increased microbial biomass C, N, and related metabolites, leading to a 1.29∼2.73 % increase in yield compared to WS. Meanwhile, RS promoted Nitrospira abundance as well as pterin and flavonoid metabolites associated with mcrA inhibition, while decreasing Anaeromyxobacter abundance, ammonium N, and DOC content, resulting in an increase in the pmoA / mcrA ratio and a noticeable drop in CH 4 emissions compared to WS. RS combined with IBF and AWD is a more sustainable integrated practice in light of the synergistic improvement in rice production and environmental benefits. The results reveal that optimizing N and water management can synergize high-yield and low-carbon by regulating rhizosphere microenvironment in rice production under crop straw incorporation. [Display omitted] • Straw incorporation combined with IBF enhances microbial N supply and rice yield. • Straw co-application with IBF and AWD optimizes rice yield and CH 4 emissions. • RS exhibits a higher rice yield and lower CH 4 emissions compared to WS. • WS increases Anaeromyxobacter abundance and DOC, promoting the methanogens. • Higher Nitrospira abundance, pterins, and flavonoids in RS inhibit methanogens. [ABSTRACT FROM AUTHOR]

This research explores possible options to reduce greenhouse gas (GHG) emissions in the Australian dairy industry by (1) including an environmental component in the national breeding program and (2) estimating the economic and environmental impacts of implementation of the subsequent indexes. A total of 12 possible selection indexes were considered. These indexes were developed to predict changes in gross per-animal methane production (using 3 scenarios depending on availability and efficacy of a direct methane trait breeding value prediction) with 4 different carbon prices, integrating them into an augmentation of the current conventional national selection index. Although some economic response is lost with inclusion of the GHG subindexes in the Balanced Performance Index, options do exist where this loss is marginal and, even in scenarios where all selection pressure is based on the environmental weighting, economic progress is still made in all cases. When including environmental traits within an index, if a relatively low percentage of economic gain or index progression is sacrificed, then approximately 40 to 50% of the maximum possible reductions in emissions may be achieved. This concurrent selection of estimated breeding values that have a correlated favorable response in emissions in addition to direct selection on a residual methane trait allows a high level of methane reduction to be achieved with a realized cost to farmers that is far lower than the economic value placed on carbon. By implementing a GHG subindex in the national breeding program, we can achieve up to a 7.9% decrease in residual methane and 9 times the reduction in gross emissions in 10 yr, compared with the current breeding program, with little to no cost to farmers. By 2050, selection based on one of the more moderate index scenarios at a carbon price of AUD$250/t (AUD$1 = US$0.71), or opportunity cost to farmers of AUD$87.22, will reduce gross emissions by 8.23% and emissions intensity by 21.25%, therefore offering a mitigation strategy that will be effective at reducing emissions with little compromise to profit. [ABSTRACT FROM AUTHOR]

• Methane emissions were measured at 23 Danish landfills with gas collection. • Gas collection efficiency was calculated using methane emission and collection rate. • The average gas collection efficiency was 50% ranging from 13 to 86% • Gas collection efficiency can be used to regulate emissions from landfills. Globally, landfills are an important source of anthropogenic methane emissions. Regulations require landfill gas be managed to reduce emissions, and some landfills have therefore installed gas collection systems to recover energy and mitigate methane emissions. However, the efficiency of such systems is seldom evaluated. This paper presents the gas collection efficiencies of 23 Danish landfills and suggests how these values could be used to regulate landfill methane emissions in Denmark. Methane emissions from all sites were measured using the tracer gas dispersion method, and gas collection efficiencies were calculated using the ratio of the methane collection rate to the sum of the collection and emission (and oxidation) rates. Gas collection efficiencies ranged between 13 and 86% with an average of 50% – a value lower than for Swedish (58%), UK (64%) and US (63%) landfills. Possible reasons for the inefficiency of gas collection systems in Denmark include shallow gas collection pipes, leakage from installations (e.g. leachate wells, gas engines), low gas recovery due to minimal gas production or a lack of gas collection in active waste cells. It is suggested to use gas collection efficiency to regulate landfills and help them reach a particular methane mitigation goal. Gas collection efficiency that falls below the target mitigation rate would in turn trigger actions to reduce landfill methane emissions. At sites where the quality of the collected gas is too low to operate a gas engine, the installed gas collection system could be retrofitted to a biocover system designed for methane oxidation. [ABSTRACT FROM AUTHOR]

This study was conducted to examine the effect of method of diet delivery to dairy cows on enteric CH 4 emission, milk production, rumen fermentation, nutrient digestion, N excretion, and manure CH 4 production potential. Sixteen lactating cows were used in a crossover design (35-d period) and fed ad libitum twice daily a diet [52:48, forage:concentrate ratio; dry matter (DM) basis] provided as forages and concentrates separately (CF) or as a total mixed ration (TMR). For the CF treatment, concentrates were offered first followed by mixed forages 45 min afterward. Method of diet delivery had no effect on DM intake, but neutral detergent fiber (NDF) intake was greater when the diet was delivered as TMR as compared with CF. Apparent total-tract digestibility of DM, crude protein, and gross energy was slightly (1 percentage unit) lower when the diet was offered as TMR than when offered as CF. In contrast, NDF digestibility was greater when the cows were fed TMR versus CF. Although average daily ruminal pH was not affected by method of diet delivery, daily duration of ruminal pH <5.6 was less when the diet was delivered as TMR as compared with CF (0.9 h/d versus 3.7 h/d). Delivering the diet as TMR increased ruminal total volatile fatty acid and NH 3 concentrations, but had no effect on acetate, propionate, or branched-chain volatile fatty acid molar proportions. Yields of milk, milk fat, or milk protein, and milk production efficiency (kg of milk/kg of DM intake or g of N milk/g of N intake) were not affected by the method of diet delivery. Daily production (g/d), yield (% gross energy intake), and emission intensity (g/kg of energy-corrected milk) of enteric CH 4 averaged 420 g/d, 4.9%, and 9.6 g/kg and were not affected by diet delivery method. Fecal N output was greater when the diet was delivered as TMR versus CF, whereas urinary N excretion (g/d, % N intake) was not affected. Manure volatile solids excretion and maximal CH 4 production potential were not affected by method of diet delivery. Under the conditions of this study, delivering the diet as concentrates and forages separately versus a total mixed ration had no effect on milk production, enteric CH 4 energy losses, urinary N, or maximal manure CH 4 emission potential. However, feeding the diet as total mixed ration compared with feeding concentrates and forages separately attenuated the extent of postprandial decrease in ruminal pH, which has contributed to improving NDF digestibility. [ABSTRACT FROM AUTHOR]

• A web – based platform for methane emission modelling from landfills is proposed. • Model integration technology with databases and GIS are described. • The inverse algorithm is built to determine the emission source capacity. • To quantify CH 4 emissions for SKER about 158,977.77 tons in the period 2019–2030. • The results of CH 4 pollution dispersion simulation is performed. This study developed a platform using a modelling and web technology approach to estimate methane emissions from landfills to assess methane emissions across the region. The web technology-based software EnLandFill, which was developed, allows users to log in, interact with landfill databases, and document and extract information regarding landfill emissions. Models that integrate web technology with databases and geographic information systems (GIS) are described. One of the achievements of this study was the development of an inverse algorithm to determine the waste source capacity according to a dispersion model, accounting for complex terrain and meteorological time-series data extracted from the Weather Research and Forecasting (WRF) model. EnLandFill software was applied to quantify CH 4 emissions for key developing regions, predicting approximately 158,977 tonnes, equivalent to 167,786,878 m3 of CH 4 for the period of 2019 – 2030. The software also allows the evaluation of the scope and level of impacts of landfill emissions under given meteorological conditions. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the effect of isonitrogenous substitution of solvent-extracted soybean meal (SBM) with solvent-extracted canola meal (CM) on enteric CH 4 production, ruminal fermentation characteristics (including protozoa), digestion (in situ and apparent total-tract digestibility), N excretion, and milk production of dairy cows. For this purpose, 16 lactating Holstein cows, of which 12 were ruminally cannulated, were used in a replicated 4 × 4 Latin square (35-d periods; 14-d adaptation). The cows averaged (mean ± SD) 116 ± 23 d in milk, 692 ± 60 kg of body weight, and 47.5 ± 4.9 kg/d of milk production. The experimental treatments were control diet (no CM; 0%CM) and diets supplemented [dry matter (DM) basis] with 7.9% CM (8%CM), 15.8% CM (16%CM), or 23.7% CM (24%CM) on a DM basis. The forage:concentrate ratio was 52:48 (DM basis) and was similar among the experimental diets. Canola meal was included in the diet at the expense of SBM and soybean hulls, whereas the percentages of the other diet ingredients were the same. Intake of DM increased linearly, whereas apparent total-tract digestibility of DM, crude protein, neutral detergent fiber, and gross energy (GE) declined linearly as CM inclusion in the diet increased. Total volatile fatty acids concentration and butyrate molar proportion decreased linearly, whereas molar proportion of propionate increased linearly, and that of acetate was unaffected by CM inclusion in the diet. Ruminal ammonia concentration was not affected by inclusion of CM in the diet. Energy-corrected milk (ECM) yield increased linearly (up to 2.2 kg/d) with increasing CM percentage in the diet, whereas milk production efficiency averaged 1.63 kg of ECM/kg of DM intake and was unaffected by CM inclusion in the diet. Daily CH 4 production decreased linearly with increasing CM percentage in the diet (489, 475, 463, and 461 g/d for 0%CM, 8%CM, 16%CM and 24%CM diets, respectively). As a consequence, CH 4 emission intensity (g of CH 4 /kg of ECM) also declined linearly by up to 10% as the amount of CM increased in the diet. Methane production also decreased linearly when expressed relative to GE intake (5.7, 5.2, 5.1, and 4.9% for 0%CM, 8%CM, 16%CM and 24%CM diet, respectively). Quantity of manure N excretion was not affected by replacing SBM with CM; however, N excretion shifted from urine to feces as dietary percentage of CM increased, suggesting reduced potential for N volatilization. Results from this study show that replacing SBM with CM as a protein source in dairy cow diets reduced enteric CH 4 emissions (g/d, % of GE intake, and adjusted for milk production) and increased milk production. The study indicates that CM can successfully, partially or fully, replace SBM in lactating dairy cow diets, with positive effects on animal productivity and the environment (i.e., less enteric CH 4 emission and urinary N excreted). We conclude that compared with SBM, inclusion of CM meal in dairy cow diets can play a key role in reducing the environmental footprint of milk production. [ABSTRACT FROM AUTHOR]

Methane is a short-lived and potent greenhouse gas with a rapid warming effect. Gas stoves and water heaters, which are the most widely used domestic gas appliances (over 250 million in China), emit methane because of incomplete combustion and leakage. This study quantified the methane emissions of these two gas appliances at different ages through field measurements and laboratory tests to assess their impact on the climate. Their methane concentrations typically spiked quickly and decayed rapidly during ignition and extinguishment, but were low and stable during the steady-on state. Tankless water heaters emitted 1.69‰ (95% confidence interval: 1.44‰, 2.01‰) of the natural gas consumed, primarily during the on-pulse phase. More than four-fifths of the methane emissions from gas stoves occurred in the steady-on state, and the emission rates were positively correlated with the age of the gas stoves (r2 = 0.79, p < 0.001). Therefore, approximately 28.1 (27.5, 28.6) Gg of methane emissions annually can be attributed to Chinese residential gas appliances, corresponding to a 0.8 Mt. carbon dioxide equivalent over a 100-y scale. [Display omitted] • Chinese residential gas appliances contribute 28.1 Gt of annual methane emissions. • Methane emissions from gas appliances peak at ignition and extinguishment. • Over 80% of the methane emissions from gas stoves originate in the steady-on phase. • Methane emissions from overage gas appliances remain at a high level in operation. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of incorporating rice straw and orange leaves into the diets for goats. Ten Murciano-Granadina goats at mid lactation weighing 45 ± 0.3 kg were used in a crossover design. Two isoproteic and isoenergetic diets (180 g/kg DM and 17 MJ/kg DM, respectively) with alfalfa hay as forage source (33% of DM) were fed. A control diet (CON) incorporated barley as energy source and soy hulls as fiber component. The experimental diet (ORG) replaced barley and soy hulls with orange leaves (19% on DM basis), rice straw (12%, on DM basis) and soya oil (2%). Peas and horsebeans were the protein source in both diets. Each goat received the 2 treatments in 2 periods. Goats were fed the experimental diets and after 14 d on their respective treatments moved to individual metabolism cages for another 7 d. Subsequently, feed intake, total fecal and urine output and milk yield were recorded daily over the first 5 d. During the next 2 d ruminal fluid and blood samples were collected, and then individual gas-exchange measurements were recorded by a mobile open-circuit indirect calorimetry system using a head box. No differences in dry matter intake were detected, and apparent total-tract digestibility was greater in CON than ORG. Efficiency of metabolizable energy intake for milk and maintenance also was lower in response to ORG (0.65 vs. 0.63), with energy balance being negative (−12 kJ/kg of BW0.75) due to mobilization of fat (−16 g/animal vs. 68 g/animal for ORG and CON, respectively). Although actual milk yield was lower in goats fed ORG (2.32 vs. 2.06 kg/d, respectively), energy-corrected milk did not differ (2.81 kg/d on average). In terms of milk quality, milk fat content, and concentrations of monounsaturated (18.54 vs. 11.55 g/100 g milk fat) and polyunsaturated fatty acids (5.75 vs. 3.99 g/100 g milk fat) were greater in goats fed ORG. Based on various indices, the milk produced by ORG would be less atherogenic and thrombogenic than CON milk. Compared with CON, enteric CH 4 emission was lower due to feeding ORG (reduction of 38 g CH 4 /kg milk fat). Data suggest that greater fat mobilization in goats fed ORG might have been due to the apparent lack of synchrony between degradable protein and carbohydrate and the lipogenic nutrients associated with the lower cereal content of the ORG diet. Thus, goats fed ORG seemed to rely more on fat depots to help meet energy requirements and reach optimal performance. As such, the lower content of glucogenic nutrients in ORG did not favor body fat deposition and partitioning of ME into body tissue. Overall, responses in terms of CH 4 emissions and milk quality suggest that inclusion of rice straw and orange leaves in diets for small ruminants could be a valuable alternative to reuse, recycle and revalue agricultural by-products. [ABSTRACT FROM AUTHOR]

This study was conducted to examine the effect of active dry yeast (ADY) supplementation on lactation performance, ruminal fermentation patterns, and CH 4 emissions and to determine an optimal ADY dose. Sixty Holstein dairy cows in early lactation (52 ± 1.2 DIM) were used in a randomized complete design. Cows were blocked by parity (2.1 ± 0.2), milk production (35 ± 4.6 kg/d), and body weight (642 ± 53 kg) and assigned to 1 of 4 treatments. Cows were fed ADY at doses of 0, 10, 20, or 30 g/d per head for 91 d, with 84 d for adaptation and 7 d for sampling. Although dry matter intake was not affected by ADY supplementation, the yield of actual milk, 4% fat-corrected milk, milk fat yield, and feed efficiency increased quadratically with increasing ADY supplementation. Yields of milk protein and lactose increased linearly with increasing ADY doses, whereas milk urea nitrogen concentration and somatic cell count decreased quadratically. Ruminal pH and ammonia concentration were not affected by ADY supplementation, whereas ruminal concentration of total volatile fatty acid increased quadratically. Digestibility of dry matter, organic matter, neutral detergent fiber, acid detergent fiber, nonfiber carbohydrate, and crude protein increased quadratically with increasing ADY supplementation. Supplementation of ADY did not affect blood concentration of total protein, triglyceride, aspartate aminotransferase, and alanine aminotransferase, whereas blood urea nitrogen, cholesterol, and nonesterified fatty acid concentrations decreased quadratically with increasing ADY supplementation. Methane production was not affected by ADY supplementation when expressed as grams per day or per kilogram of actual milk yield, dry matter intake, digested organic matter, and digested nonfiber carbohydrate, whereas a trend of linear and quadratic decrease of CH 4 production was observed when expressed as grams per kilogram of fat-corrected milk and digested neutral detergent fiber. In conclusion, feeding ADY to early-lactating cows improved lactation performance by increasing nutrient digestibility. The optimal ADY dose should be 20 g/d per head. [ABSTRACT FROM AUTHOR]

Methane is a greenhouse gas of high interest to the dairy industry, with 57% of Australia's dairy emissions attributed to enteric methane. Enteric methane emissions also constitute a loss of approximately 6.5% of ingested energy. Genetic selection offers a unique mitigation strategy to decrease the methane emissions of dairy cattle, while simultaneously improving their energy efficiency. Breeding objectives should focus on improving the overall sustainability of dairy cattle by reducing methane emissions without negatively affecting important economic traits. Common definitions for methane production, methane yield, and methane intensity are widely accepted, but there is not yet consensus for the most appropriate method to calculate residual methane production, as the different methods have not been compared. In this study, we examined 9 definitions of residual methane production. Records of individual cow methane, dry matter intake (DMI), and energy corrected milk (ECM) were obtained from 379 animals and measured over a 5-d period from 12 batches across 5 yr using the SF 6 tracer method and an electronic feed recording system, respectively. The 9 methods of calculating residual methane involved genetic and phenotypic regression of methane production on a combination of DMI and ECM corrected for days in milk, parity, and experimental batch using phenotypes or direct genomic values. As direct genomic values (DGV) for DMI are not routinely evaluated in Australia at this time, DGV for FeedSaved, which is derived from DGV for residual feed intake and estimated breeding value for bodyweight, were used. Heritability estimates were calculated using univariate models, and correlations were estimated using bivariate models corrected for the fixed effects of year-batch, days in milk, and lactation number, and fitted using a genomic relationship matrix. Residual methane production candidate traits had low to moderate heritability (0.10 ± 0.09 to 0.21 ± 0.10), with residual methane production corrected for ECM being the highest. All definitions of residual methane were highly correlated phenotypically (>0.87) and genetically (>0.79) with one another and moderately to highly with other methane candidate traits (>0.59), with high standard errors. The results suggest that direct selection for a residual methane production trait would result in indirect, favorable improvement in all other methane traits. The high standard errors highlight the importance of expanding data sets by measuring more animals for their methane emissions and DMI, or through exploration of proxy traits and combining data via international collaboration. [ABSTRACT FROM AUTHOR]

• 2.8 t ha−1 biochar annually increased paddy soil nutrients over three years. • 2.8 t ha−1 biochar annually significantly reduced methane emissions over three years. • 2.8 t ha−1 biochar annually steadily increased methanotroph abundance. A sustainable biochar strategies on increasing crop yield and mitigating CH 4 emissions over successive years is unknown. Thus, on-site equivalent rice straw biochar-returning (ERSC, biochar at 2.8 t ha−1 annual) were compared with on-site equivalent rice straw- returning (RS, rice straw at 8 t ha−1 annual) and high application rate biochar-returning (RSCH, biochar at 22.5 t ha−1 only in the first year). The RS and RSCH treatments increased rice production by 10.1% and 11.8% on average, respectively. The ERSC treatment continually increased rice production by 8.0%, 1.6% and 7.3% in three successive years. The ERSC treatment had a cumulative effect on the soil nutrients phosphorus (P), potassium (K), and magnesium (Mg), as well as increasing total carbon (TC) and total nitrogen (TN) and continuously reducing the effect of soil available aluminum (Al). The RS treatment significantly promoted CH 4 emissions while the ERSC treatment reduced methane emissions by 43%, 31% and 30% and the RSCH treatment reduced methane emissions by 52%, 22% and14% in three successive years. Compared with RSCH, ERSC showed the best long-term stable effect on methane emission mitigation in three successive years. This might result from the fact that fresh biochar promoted anaerobic oxidation of methane. This research gives us scientific evidence that an on-site equivalent rice straw biochar-returning strategy may be a promising method for sustaining rice production and mitigating methane emissions. [ABSTRACT FROM AUTHOR]

Earlier studies have shown that plants produce methane (CH 4) under aerobic conditions, and that this emission is not microbial in nature. However, the precursors of aerobic CH 4 remain under debate, and the combined effects of environmental factors on plant-derived CH 4 requires further attention. The objective of this study was to determine the interactive effects of temperature and light intensity on CH 4 and other relevant plant parameters in canola (Brassica napus L.). Plants were grown under two temperature regimes (22/18 °C and 28/24 °C, 16 h light/8 h dark) and two light intensities (300 and 600 μmol photons m−2 s−1) for 21 days after one week of growth under 22/18 °C (16 h light/8 h dark). In this study, higher temperature had little effects on CH 4 emissions from plants, indicating the mitigating effects of higher light intensity. Higher light intensity, however, significantly decreased CH 4 , which was inversely related to plant dry mass. Higher light intensity decreased stem height, leaf area ratio, chlorophyll, nitrogen balance index, leaf moisture, methionine (Met) and ethylene (C 2 H 4), but increased specific leaf mass, photochemical quenching, flavonoids, epicuticular wax, lysine and tyrosine. The results revealed that increased CH 4 emissions from plants could be related to changes in plant physiological activities, which portrayed themselves in increased C 2 H 4 evolution, and methylated amino acids, such as Met. We conclude that higher light intensity reduces Met and, in turn, CH 4 and C 2 H 4 emissions, but lower light intensity enhances CH 4 formation through cleavage of methyl group of amino acids by reactive oxygen species, as previously suggested. • Environmental stressors adversely affect plant growth and physiological processes. • Higher light intensity decreases plant methionine and methane emissions. • Plant-derived methane is inversely related to plant dry mass. • It is important to understand methane precursors and their regulating factors. [ABSTRACT FROM AUTHOR]

The objective of this experiment was to study the effects of incorporating lemon leaves and rice straw into the compound feed of diets for dairy goats. Ten Murciano-Granadina dairy goats (n = 5 per group) in mid-lactation were used in a crossover design experiment (2 treatments across 2 periods). Goats were fed a mixed ration with barley grain (control, CON) or CON plus lemon leaves [189 g/kg of dry matter (DM)] and rice straw (120 g/kg of DM) in place of barley grain (LRS). Soybean oil (19 g/kg of DM) was added to the LRS diet to make it isoenergetic (17 MJ of gross energy/kg of DM) relative to CON. After 14 d on their respective treatments, goats were allocated to individual metabolism cages for another 7 d. Subsequently, feed intake, total fecal and urine output, and milk yield were recorded daily over the first 5 d. During the last 2 d, ruminal fluid and blood samples were collected, along with individual gas exchange measurements recorded by a mobile open-circuit indirect calorimetry system using a head box. No differences in DM intake were detected, and ME intake in LRS was lower than in CON (1,095 vs. 1,180 kJ/kg of metabolic body weight). No differences were observed in milk production, but milk fat content was greater in LRS (6.4%) than in CON (5.6%). Greater concentrations of monounsaturated (14.94 vs. 11.96 g/100 g of milk fat) and polyunsaturated fatty acids (4.53 vs. 4.03 g/100 g of milk fat) were detected in the milk of goats fed LRS compared with CON. Atherogenicity (2.68 vs.1.91) and thrombogenic (4.58 vs. 2.81) indices were lower with LRS compared with CON. Enteric CH 4 emission was lower in LRS (24.3 g/d) compared with CON (31.1 g/d), probably due to the greater lipid content and unsaturated fatty acid profile of lemon leaves and the soybean oil added in the LRS diet. Overall, data suggest that incorporating lemon leaves and rice straw into lactating goat diets is effective in reducing CH 4 emissions while allowing improvements in milk fat production and milk thrombogenic index without affecting production performance. Thus, their inclusion in compound feeds fed to small ruminants appears warranted and would have multiple positive effects, as on efficiency of nutrient use, human health, and the environment. [ABSTRACT FROM AUTHOR]

• In-situ CH 4 emission in a loess-gravel capillary barrier cover (CBC) was studied. • Soil moisture and temperature in the top 0.2 m dominated CH 4 oxidation rate. • CH 4 oxidation rate and maximum CH 4 emission were larger in summer than in winter. • CH 4 emission reduced a lot as water content increased above 40% at depth of 0.85 m. • Capillary barrier effects in the CBC exacerbate the upslope CH 4 emission. The methane emission in a loess-gravel capillary barrier cover (CBC) in winter and summer was investigated by constructing a full-scale testing facility (20 m × 30 m) with a slope angle of 14.5° at a landfill in Xi'an, China. Weather conditions, methane emission, gas concentration, temperature, and volumetric water content (VWC) in the CBC were measured. The temperature and moisture in the CBC showed a typical seasonal pattern of warm and dry in summer and cold and wet in winter. Accordingly, the maximum methane oxidation rate and methane emission were higher in summer. The mean methane influx and methane emission decreased significantly as the VWC increased beyond 40% (i.e., a degree of saturation 0.85) at a depth of 0.85 m, which was near the loess/gravel interface. At this depth, more water was presented in the loess layer in the downslope direction due to capillary barrier effects, which increased the upslope methane emission. More dominant methane emission in the middle- and upper-section of the CBC occurred in summer than in winter as there was less soil moisture to facilitate methane transfer. The LFG balance showed that a significant fraction of the loaded LFG was not accounted in the flux chamber measurements due to the preferential flow along the edges of the CBC. The maximum methane oxidation rate was 93.3 g CH 4 m−2 d−1, indicating the loess-gravel CBC could mitigate methane emissions after landfill closure. [ABSTRACT FROM AUTHOR]

As the second most abundant greenhouse gas after carbon dioxide, methane (CH 4) leakage and emissions pose potential climate threats and environmental problems in the midstream oil and gas storage and transportation (OGST) industry. In this study, the Tropospheric Monitoring Instrument on the Sentinel-5P satellite was adopted to investigate the coverage of atmospheric CH 4 concentrations over the Zhoushan archipelago, which is China's largest OGST base. Specifically, the distribution of atmospheric CH 4 and nitrogen dioxide (NO 2) concentrations over Zhoushan in August 2022 and August 2023 were evaluated, where changes in concentrations around the OGST companies were monitored. Using surface temperature inversion and average temperature statistics, we analyzed the heat island effect in Zhoushan. The results showed that: (1) although there is limited valid data (>200 pixel/day) for Zhoushan, the amount of valid data increased from 3.2% in January 2020 to 32.3% in August 2023; (2) around the region of the OGST companies, the atmospheric CH 4 concentration shown significant variation at both the spatial and temporal scales, which may be due to the storage, loading, and unloading of petroleum products; (3) under geographic isolation conditions, NO 2 can be used as a tracer gas to track the CH 4 emissions from OGST companies; and (4) Surface temperature analysis underscores OGST companies' contribution to Zhoushan's urban heat island effect, with local average temperature increases outstripping broader national trends, highlighting the intricate interplay of human and natural factors in the city-scale climate dynamics. [ABSTRACT FROM AUTHOR]

Uncovering the environmental drivers and revealing the balance between methanogenesis and methanotrophy under different watering regimes are vital for understanding methane (CH 4) emissions in rice paddies. Although the mechanisms and impacts of watering regimes on plant community structures in rice paddies have been intensively investigated, the methanogenic and methanotrophic reactions under drying stress that regulate CH 4 emissions remain unclear. Here, we examined the watering regimes of rice fields to elucidate how continuous flooding and dry cultivation impacted and regulated CH 4 emissions. Water-saving regimes (dry cultivation) significantly decreased CH 4 emissions (70–90 %) compared to the flooding treatment. The methanogenic and methanotrophic abundance, composition and structures were stable under the two watering regimes, while microbial interactions demonstrated that the dry cultivation had fewer positive links to methanogens in contrast to flooding. Furthermore, the more positive links to methanotrophs and limited electron transfer within rice plant communities under dry cultivation were observed, which subsequently restricted methanogenesis, translating to lower CH 4 emissions. Dry cultivation also weakened the correlations between environmental factors and methanogens, albeit strengthened the links to methanotrophs. Flooding treatment exhibited significantly positive electrical conductivity and dissolved organic carbon-methanogen correlations, which might have explained the higher CH 4 emissions than the dry cultivation. These findings suggested that drying treatment reduced microbial connectivity and abundance of methanogenic drivers in the microbial network, which decreased the CH 4 emissions compared with flooding treatment. • Drying and flooding treatments did not alter microbial communities or their abundance. • Drying treatment induced fewer links to methanogens but more so to methanotrophs in contrast to flooding. • Microbial networks and their interactions determined CH 4 emissions under experimental regimes. • Drying treatment weakened methanogenic activities and their connections with the environment. [ABSTRACT FROM AUTHOR]

• CH 4 and CO 2 fluxes from two wetlands in northeast China are presented. • Most variations of CH 4 were distributed at time scales of several days to some months. • Soil temperature and thaw depth imposed alternated influences on CH 4 at the peatland. • Soil temperature and plant productivity influenced CH 4 emissions at the marsh. • Both wetlands were carbon sinks while the marsh had a net positive radiative forcing. Quantifying net CO 2 exchange (NEE) and CH 4 emissions of northern wetlands and their responses to biophysical controls are central to understanding the role of wetlands in global climate change. This study presents two growing seasons of observations of CO 2 and CH 4 fluxes by eddy covariance technique from a permafrost peatland and an inundated marsh in northeast China. Wavelet analysis was used to explore the temporal multi-scale variations of NEE and CH 4 fluxes and their biophysical controls. NEE showed prominent variations at the diel and the seasonal scales. However, most CH 4 variance was distributed at time scales longer than one day. At the permafrost peatland wavelet analysis revealed strong spectral coherency and alternating coherence between soil temperature and CH 4 fluxes during the spring and summer seasons and between thaw depth and CH 4 fluxes in the late growing season, with the suggestion of an as yet unknown coherence at longer timescales than could be resolved with just growing season records. At the marsh, soil temperature and CH 4 flux showed strong spectral coherency throughout the growing seasons and gross ecosystem production (GEP) additionally imposed its influence on CH 4 mainly during the most active part of the growing season. The growing season average CH 4 emission from the peatland (0.7 g C CH 4 m−2) was quite small and was negligible compared to its growing season NEE (−74.2 g C CO 2). In contrast, the growing season CH 4 emission from the marsh (average 31.1 g C CH 4 m−2) was considerably higher and accounted for about 16.2 % of its NEE (−191.7 g C CO 2 m−2). Although the two wetlands were net carbon sinks during the growing seasons and the permafrost peatland had a negative radiative forcing (i.e., cooling effect), the high CH 4 emissions from the marsh resulted in a net positive radiative forcing (i.e., warming effect). To understand the function of northern wetlands in the global carbon cycle, continuous field observations of these greenhouse gases are vital. [ABSTRACT FROM AUTHOR]

Currently, various attempts are being made to implement breeding schemes aimed at producing low methane (CH 4) emitting cows. We investigated the persistence of differences in CH 4 emission between groups of cows categorized as either low or high emitters over a 5-mo period. Two feeding regimens (pasture vs. indoors) were used. Early- to mid-lactation Holstein Friesian cows were categorized as low or high emitters (n = 10 each) retrospectively, using predictions from milk mid-infrared (MIR) spectra, before the start of the experiment. Data from MIR estimates and from measurements with the GreenFeed (GF; C-Lock Technology Inc., Rapid City, SD) system over the 5-mo experiment were combined into 7-, 14-, and 28-d periods. Feed intake, eating and ruminating behavior, and ruminal fluid traits were determined in two 7-d measurement periods in the grazing season. The CH 4 emission data were analyzed using a split-plot ANOVA, and the repeatability of each of the applied methods for determining CH 4 emission was calculated. Traits other than CH 4 emission were analyzed for differences between low and high emitters using a linear mixed model. The initial category-dependent differences in daily CH 4 production persisted over the subsequent 5 mo and across 2 feeding regimens with both methods. The repeatability analysis indicated that the biweekly milk control scheme, and even a monthly scheme as practiced on farms, might be sufficient for confirming category differences. However, the relationship between CH 4 data estimated by MIR and measured with GF for individual cows was weak (R2 = 0.26). The categorization based on CH 4 production also generated differences in CH 4 emission per kilogram of milk; differentiation between cow categories was not persistent based on milk MIR spectra and GF. Compared with the high emitters, low emitters tended to show a lower acetate-to-propionate ratio in ruminal volatile fatty acids, whereas feed intake and ruminating time did not differ. Interestingly, the low emitters spent less time eating than the high emitters. In conclusion, the CH 4 estimation from analyzing the milk MIR spectra is an appropriate proxy to form and regularly control categories of cows with different CH 4 production levels. The categorization was also sufficient to secure similar and persistent differences in emission intensity when estimated by MIR spectra of the milk. Further studies are needed to determine whether MIR data from individual cows are sufficiently accurate for breeding. [ABSTRACT FROM AUTHOR]

The objective of this study was to examine the effects of feeding conventional corn silage (CCS) or brown midrib corn silage (BMCS) to dairy cows on CH 4 emissions from stored manure. Eight lactating cows were fed (ad libitum) a total mixed ration (forage:concentrate ratio 65:35; dry matter basis) containing 59% (dry matter basis) of either CCS or BMCS. Feces and urine were collected from each cow and mixed with residual sludge obtained from a manure storage structure. Manure was incubated for 17 wk at 20°C under anaerobic conditions (O 2 -free N 2) in 500-mL glass bottles. Methane emissions and changes in chemical composition of the manure were monitored during the incubation period. The total amount of feces and urine excreted was higher for cows fed BMCS than for cows fed CCS [8.6 vs. 6.5 kg/d of volatile solids (VS)]. Manure from cows fed BMCS emitted more CH 4 than manure from cows fed CCS (173 vs. 146 L/kg of VS) throughout the incubation period. Similarly, VS and neutral detergent fiber losses throughout incubation were higher for manure from cows fed BMCS versus cows fed CCS (37.6 vs. 30.6% and 46.2 vs. 31.2%, respectively). Manure NH 3 concentration (79% of total manure N) was not affected by corn silage cultivar. Results of this study show that using a more digestible corn silage cultivar (BMCS vs. CCS) may increase the contribution of manure to CH 4 emissions, and may offset gain achieved by reducing enteric CH 4 emissions. [ABSTRACT FROM AUTHOR]

Aquatic system is the major source of atmospheric methane. This study explored the influences of ferrihydrite, which is widely existed in natural aquatic system, on methane emission. Results showed that the presence of ferrihydrite led to 26.4% more methane emission. By tracking the transformation of organic compounds, it is revealed that the enhanced methane emission was attributed to greater hydrolysis and degradation of refractory compounds. More specifically, the remaining humic-like substances (HS) in ferrihydrite group (46.4 mg/L-C) were only half of that in control group (80.1 g/L-C) after 30-day incubation. The X-ray photoelectron spectroscopy spectrum confirmed the more active oxidation of organics occurred in ferrihydrite group. It was also found that ferrihydrite aided in sustaining microbial activity at stationary and starvation phases. Further study on microbial communities found that ferrihydrite promoted the enrichment of both functional and electroactive genera. This study provides insights into the greenhouse gas emission in natural environment. Unlabelled Image • Ferrihydrite enhanced methane emission by 26.4%. • Ferrihydrite facilitated the biodegradation of recalcitrant compounds, such as HS. • XPS spectrum evidenced dehydrogenation oxidation process under anaerobic condition. • Ferrihydrite aided in sustaining microbial activity during substrate limited phases. • Functional and electroactive genera were enriched with the presence of ferrihydrite. [ABSTRACT FROM AUTHOR]

This study aimed to compare measurements of methane (CH 4) and carbon dioxide (CO 2) concentrations in the breath of dairy cows kept in commercial conditions using the Fourier-transform infrared spectroscopy (FTIR) and nondispersive infrared spectroscopy (NDIR) methods. The measurement systems were installed in an automated milking system. Measurements were carried out for 5 d using both systems during milkings. The measurements were averaged per milking, giving 467 observations of CH 4 and CO 2 concentrations of 44 Holstein Friesian cows. The Pearson correlation between observations from the 2 systems was 0.86 for CH 4 , 0.84 for CO 2 , and 0.88 for their ratio. The repeatability of FTIR (0.53 for CH 4 , 0.57 for CO 2 , and 0.28 for their ratio) was somewhat higher than that of NDIR (0.57 for CH 4 , 0.47 for CO 2 , and 0.25 for their ratio). The coefficient of individual agreement was 0.98 for CH 4 , 0.89 for CO 2 , and 0.89 for their ratio; the concordance correlation coefficient was 0.48 for both gases and 0.24 for their ratio. We showed that FTIR and NDIR give similar results in commercial farm conditions. They can therefore be used interchangeably to generate a larger data set, which could then be further used for genetic evaluation. [ABSTRACT FROM AUTHOR]

Straw-return methods that neither negatively impact yield nor bring environmental risk are ideal patterns. To attain this goal, it is necessary to conduct field observation to evaluate the environmental influence of different straw-return methods. Therefore, we conducted a 2-year field study in 2015–2017 to investigate the emissions of methane (CH 4) and nitrous oxide (N 2 O) and the changes in topsoil (0–20 cm) organic carbon (SOC) density in a typical Chinese rice-wheat rotation in the Eastern China. These measurements allowed a complete greenhouse gas accounting (net GWP and GHGI) of five treatments including: FP (no straw, plus fertilizer), FS (wheat straw plus fertilizer), FB (straw-derived biochar plus fertilizer), FSDI (wheat straw with straw-decomposing microbial inoculants plus fertilizer) and CK (control: no straw, no fertilizer). Average annual SOC sequestration rates were estimated to be 0.20, 0.97, 1.97 and 1.87 t C ha−1 yr−1 (0–20 cm) for the FP, FS, FB and FSDI treatments respectively. Relative to the FP treatment, the FS and FSDI treatments increased CH 4 emissions by 12.4 and 17.9% respectively, but decreased N 2 O emissions by 19.1 and 26.6%. Conversely, the FB treatment decreased CH 4 emission by 7.2% and increased N 2 O emission by 10.9% compared to FP. FB increased grain yield, but FS and FSDI did not. Compared to the net GWP (11.6 t CO 2 -eq ha−1 yr−1) and GHGI (1.20 kg CO 2 -eq kg−1 grain) of FP, the FS, FB and FSDI treatments reduced net GWP by 12.6, 59.9 and 34.6% and GHGI by 10.5, 65.8 and 37.7% respectively. In rice-wheat systems of eastern China, the environmentally beneficial effects of returning wheat straw can be greatly enhanced by application of straw-decomposing microbial inoculants or by applying straw-derived biochar. Image 1 1. Global warming potentials of different straw-return methods compared in two-year rice-wheat study. 2. Straw retention increased soil CH 4 and N 2 O emitted, but not soil organic C (SOC). 3. Straw plus microbial inoculants increased SOC and CH 4 emitted, but decreased N 2 O. 4. Straw-derived biochar increased SOC, crop yields and N 2 O emitted, but reduced CH 4. 5. Global warming potential reduced by straw plus microbial inoculants or straw-biochar. [ABSTRACT FROM AUTHOR]

Total CH 4 emissions map of the Chinese livestock sector for 2014 at a resolution of 1-km × 1-km. • New high-resolution CH 4 emissions for China's livestock sector were estimated. • Spatial-temporal emissions revealed a correlation between policies and emissions. • Northward shift of emission hotspots induced by economic and policy incentives. • Hunan Province ranks highest in priority for the implementation of technical measures. • A combination of composting and anaerobic digestion scenario is recommended. China contributes approximately 10% of the total global methane (CH 4) emissions from its livestock sector. However, existing inventories of CH 4 emissions from the livestock sector involve significant uncertainty, and the reduction potentials and spatially varying efficiencies of different technical options (adding lipid to diets, acidification, composting, anaerobic digestion, and the combination of composting and anaerobic digestion) have not been systematically assessed at the provincial level. Here, we used a bottom-up approach to compile an up-to-date high-resolution CH 4 emission inventory for the livestock sector in China using provincial condition-specific emission factors by considering the gross energy intake and the ambient temperature at the provincial level. A 1-km × 1-km gridded map was produced for 2014, and the temporal trends of the CH 4 emissions from 1978 to 2013 were re-visited. The effects of the technical mitigation options that could have been used on CH 4 emissions were further evaluated in five different scenarios. Livestock sector CH 4 emissions decreased by 1.2 Tg CH 4 per year from the period of 1999–2006 to the period of 2007–2014, and this rate was approximately 17–28% lower than previous estimates. During the period of 1978–2014, spatial-temporal emission trends indicated a possible relationship between the Chinese government policies and emissions to some extent and a northward shift of emission hotspots induced by economic and policy incentives. Hotspots with high mitigation potential and efficiency (the achieved reduction under a specific mitigation scenario divided by the baseline emissions from the species affected by the respective technical option) were also identified. The combination of composting and anaerobic digestion is a recommended policy, which can simultaneously address slurry and solid manure and significantly mitigated of CH 4 emissions. Overall, this study provides insights into the region-dependent implementation of technical options used to reduce CH 4 emissions from the livestock sector in China. [ABSTRACT FROM AUTHOR]

Respiration chambers share one analyzer working in parallel, and methane (CH 4) concentrations have to be measured at certain intervals. The maximum and minimum values in the kinetics of CH 4 emissions can be missed during the interval between measurements, which may influence the quantification of CH 4 emissions. Chambers must be opened for morning feeding and cleaning, which causes a loss of CH 4 data. Calculation methods are needed to estimate the lost CH 4 emission data, which may influence the estimated amount of daily CH 4 emissions. In this study, we measured the CH 4 emissions of 10 growing Chinese Holstein dairy heifers in respiration chambers. Methane concentrations were measured every 0.5 min to obtain the 23-h kinetics of CH 4 emissions, which were further selected at different intervals between measurements (i.e., 5, 30, 60, 120, 180, and 240 min) to evaluate the effects of interval on quantification of CH 4 emissions. The missing 1-h kinetics of CH 4 emissions before feeding were not measured, and 2 calculation methods were used to estimate the missing 1-h kinetics of CH 4 emissions: mean value of measuring period (the mean method) and the nearest value of measurement just before chamber opening (the nearest method). The results showed that the rates of CH 4 emission from 10 heifers varied from 4.56 to 11.42 g/h. The increment of intervals decreased maximum rate of CH 4 emission and increased minimum rate of CH 4 emission. Interval caused less than 5% of the difference in measuring CH 4 emissions. Although the mean method had greater estimated daily CH 4 emission than the nearest method, the difference was within 3%. The interval between measurements (≤3 h) and calculation method had little influence on enteric CH 4 emission measurements. [ABSTRACT FROM AUTHOR]

Concern over the carbon footprint of the dairy industry has led to various dietary approaches to mitigate enteric CH 4 production. One approach is feeding the electron acceptor NO 3 −, thus outcompeting methanogens for aqueous H 2. We hypothesized that a live yeast culture (LYC; Saccharomyces cerevisiae from Yea-Sacc 1026, Alltech Inc., Nicholasville, KY) would stimulate the complete reduction of NO 3 − to NH 3 by selenomonads, thus decreasing the quantity of CH 4 emissions per unit of energy-corrected milk production while decreasing blood methemoglobin concentration resulting from the absorbed intermediate, NO 2 −. Twelve lactating Jersey cows (8 multiparous and noncannulated; 4 primiparous and ruminally cannulated) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Cattle were fed diets containing 1.5% NO 3 − (from calcium ammonium nitrate) or an isonitrogenous control diet (containing additional urea) and given a top-dress of ground corn without or with LYC, with the fourth week used for data collection. Noncannulated cows were spot measured for CH 4 emission by mouth using GreenFeed (C-Lock Inc., Rapid City, SD). The main effect of NO 3 − decreased CH 4 by 17% but decreased dry matter intake by 10% (from 19.8 to 17.8 kg/d) such that CH 4 :dry matter intake numerically decreased by 8% and CH 4 :milk net energy for lactation production was unaffected by treatment. Milk and milk fat production were not affected, but NO 3 − decreased milk protein from 758 to 689 g/d. Ruminal pH decreased more sharply after feeding for cows fed diets without NO 3 −. Acetate:propionate was greater for cows fed NO 3 −, particularly when combined with LYC (interaction effect). Blood methemoglobin was higher for cattle fed NO 3 − than for those fed the control diet but was low for both treatments (1.5 vs. 0.5%, respectively; only one measurement exceeded 5%), indicating minimal risk for NO 2 − accumulation at our feeding level of NO 3 −. Although neither apparent organic matter nor neutral detergent fiber digestibilities were affected, apparent N digestibility had an interaction for NO 3 − × LYC such that apparent N digestibility was numerically lowest for diets containing both NO 3 − and LYC compared with the other 3 diets. Under the conditions of this study, NO 3 − mitigated ruminal methanogenesis but also depressed dry matter intake and milk protein yield. Based on the fact that few interactions were detected, LYC had a minimal role in attenuating negative cow responses to NO 3 − supplementation. [ABSTRACT FROM AUTHOR]

The rumen ecosystem represents a classic example of host–microbiome symbiosis. In this obligatory relationship, the host feeds on plant fibers that can only be degraded through a set of complex metabolic cascades, exclusively encoded in rumen-associated microbes. These various metabolic pathways are distributed across a multitude of microbial populations. Application of basic ecological principles to this ecosystem can contribute to profound understanding of the rules that shape it. Here, we discuss recent studies by examining the mapping between host attributes, rumen ecosystem composition, and functionality to propose simple, yet powerful concepts to guide the interpretation of microbiome data and enable a better understanding of how the system responds to perturbations. Rumen microbiomes exhibit repetitive patterns that are connected to their host attributes and can be regarded as community states. The functional groups concept serves to analyze ecosystem function and community states, as different microbial lineages can share functions; thus, combining taxonomy into functional groups enables better interpretation and understanding of the rumen ecosystem. Key junctions of functional groups at the final steps of electron flow of the rumen ecosystem can explain observed alternative community states. Niche modification by functional groups shifts between rumen microbiome community states. Host genetics and diet are connected to rumen microbiome composition and can influence rumen microbiome community states. Feedback loops of specific functional groups during rumen microbiome succession can determine rumen community states. [ABSTRACT FROM AUTHOR]

Many studies have investigated the effects of one or two environmental factors on methane (CH 4) emissions from plants at a single growth stage, but the impact that multiple co-occurring stress factors may have on emissions at different growth stages has rarely been studied. The objective of this study was to examine the effects of temperature, ultraviolet-B (UVB) radiation, and watering regime on CH 4 emissions and some relevant physiological characteristics of pea (Pisum sativum L. cv. 237 J Sundance) plants at three growth stages. We grew plants under two temperature regimes (22/18 °C and 28/24 °C; 16 h light/8 h dark), two UVB levels [0 and 5 kJ m−2 d−1] and two watering regimes (well-watered, watering plants to field capacity, and water-stressed, watering plants at wilting point). Measurements were then taken after 10, 20, and 30 days of growth under experimental conditions, following seven days of initial growth under 22/18 °C. Higher temperatures, UVB5, and water stress adversely affected photosynthesis and chlorophyll fluorescence, but increased CH 4 emissions, which decreased with increased plant age. Also, interaction of higher temperatures and UVB5 reversed the pattern of CH 4 emissions at growth stages, compared to that of other treatments. We conclude that CH 4 emission decreases with plant age, and it is affected by stress factors through changes in physiological activities of plants. • Examining the effects of multiple stress factors on methane emissions from plants is important. • High temperature, UVB radiation and water stress adversely affect plant physiological processes. • Aerobic methane emission is increased by environmental stressors, but decreased with plant age. • This study has important implications for the estimation of global methane fluxes from vegetation. [ABSTRACT FROM AUTHOR]

• Long term (3 years) CH 4 emissions from field-scale semi-aerobic test cell was studied. • CH 4 emission during wet and dry seasons were systematic measured and compared. • The presence of gas vents reduced average CH 4 emissions to half of that without them. • CH 4 hotspots developed in semi-aerobic cell after rainfall. • Gas vents maintain semi-aerobic conditions when rainwater infiltration is low. Two landfill test cells, with and without gas vents, were used to investigate the effectiveness of passive aeration, through basal leachate pipes, in mitigating methane emissions from municipal solid waste disposal in the tropical climate of Thailand. Surface methane emission rate, as well as methane content in the landfill gas, were determined for a period of three years. The results indicate that the average methane emission rate from the test cell with passive gas vents (42.13 g/t dry wt./d) was about half of that from the test cell without gas vents (90.33 g/t dry wt./d). Methane emission rates from both test cells fluctuated and were influenced by precipitation. The emission rate during the wet period in the test cell with gas vents (61.67 g/t dry wt./d) was 3 times as much as that observed during the dry period (20.95 g/t dry wt./d). The emission rate during the wet period in the test cell without gas vents (120.33 g/t dry wt./d), was twice the value of that observed during the dry period (60.32 g/t dry wt./d). The measurements also revealed the formation of methane hotspots in the test cell with passive vents after rainfall events, leading to higher localized surface emissions. Introduction of gas vents helped reduce methane emissions from solid waste landfills in a tropical region. However, rainfall should be limited to avoid turning semi-aerobic conditions into anaerobic conditions. [ABSTRACT FROM AUTHOR]