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Methanogens play an important role in the demethylation of arsenic. Soil amendments that inhibit methanogens can increase dimethylarsinic acid (DMA), which is responsible for straighthead disease in rice. A decrease in methanogenesis caused by silicate fertilizer may increase DMA concentration in paddy soils and rice grains; the relationship between these two factors and their impacts on DMA concentration remains unclear. We applied silicate fertilizer (2 Mg ha -1 ) to japonica and indica rice grown on arsenic-spiked soils and found a simultaneous reduction in methane emissions and pore-water DMA concentration, compared to no-silicate fertilization. Gene and transcript copies of mcrA and arsM, as well as dominant methanogens and arsenic-methylating microbes decreased significantly with silicate fertilization. However, the sulfate-reducing bacteria and the gene and transcript copies of dsrB did not change significantly in response to the application of silicate fertilizer to paddy soils. The abundance of arsenic methylating microbes was significantly and positively correlated with the abundance of methanogens, but not with the abundance of sulfate-reducing bacteria. Methylomonas and Methylobacter, which harbor the arsM gene, were suppressed under silicate fertilization, suggesting that they have the potential to methylate As and play a crucial role in reducing pore-water DMA in As-enriched flooded paddy soils. Increasing Fe concentration, soil pH, and Eh value decreased pore-water DMA concentration, while decreasing arsenite concentration, arsM and mcrA gene abundance decreased it. While silicate fertilization decreased arsenite and DMA concentrations in pore-water, it had no significant effect on rice DMA content, but significantly decreased arsenite content. Results reveal that methanogens and arsenic-methylating microbes have a synergistic relationship under silicate fertilization that facilitates a significant reduction in methane emissions and DMA concentration in As-enriched paddy soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Methane (CH 4 ) is the second most abundant greenhouse gas. China is the largest CH 4 emitter in the world, with coal mine methane (CMM) being one of the main anthropogenic contributions. Thus, there is an urgent need for comprehensive estimates and strategies for reducing CMM emissions in China. However, the development of effective strategies is currently challenged by a lack of information on temporal variations in the contributions of different CMM sources and the absence of provincial spatial analysis. Here, considering five sources and utilization, we build a comprehensive inventory of China's CMM emissions from 1980 to 2022 and quantify the contributions of individual sources to the overall CMM emissions at the national and provincial levels. Our results highlight a significant shift in the source contributions of CMM emissions, with the largest contributor, underground mining, decreasing from 89% in 1980 to 69% in 2022. Underground abandoned coal mines, which were ignored or underestimated in past inventories, have become the second source of CMM emissions since 1999. From 2011 to 2022, we identified Shanxi, Guizhou, and Shaanxi as the three largest CMM-emitting provinces, while the Emissions Database for Global Atmospheric Research (EDGAR) v8 overestimated emissions from Inner Mongolia, ranking it third. Notably, we observed a substantial decrease (exceeding 1 Mt) in CMM emissions in Sichuan, Henan, Liaoning, and Hunan between 2011 and 2022, which was not captured by EDGAR v8. To develop targeted CMM emission reduction strategies at the provincial level, we classified 31 provinces into four groups based on their CMM emission structures. In 2022, the number of provinces with CMM emissions mainly from abandoned coal mines has exceeded that of provinces with mainly underground mines, which requires attention. This study reveals the characteristics of the source of CMM emissions in China and provides emission reduction directions for four groups of provinces., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

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., (The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)

Rice paddy has been the main source of anthropogenic methane (CH 4 ) emissions, with significant variations among rice varieties. 2-Acetyl-1-pyrroline (2-AP) is the key component of the pleasant aroma in fragrant rice. Here, we show that fragrant rice is metabolically active in nitrogen assimilation and exhibits high levels of 2-AP and that CH 4 fluxes at the booting stage and cumulative emissions are 25.5% and 14.8% lower, respectively, in fragrant rice paddies compared with nonfragrant rice paddies. Three precursors involved in 2-AP synthesis-proline, glutamic acid, and ornithine-are identified as crucial nitrogen compounds that significantly promote CH 4 oxidation in the rhizosphere. Augmenting 2-AP synthesis, either through foliar spraying or by utilizing CRISPR-Cas9 technology to generate knockout lines of BETAINE ALDEHYDE DEHYDROGENASE 2 gene, effectively enhances CH 4 oxidation and reduces CH 4 fluxes. Our findings reveal that the 2-AP metabolic pathway coordinates the carbon/nitrogen cycle to improve nitrogen assimilation along with high 2-AP levels and mitigate CH 4 emissions in paddy ecosystems., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Mitigation of methane (CH 4 ) emissions from slurry pits within pig barns can be achieved through treatment of residual slurry left after frequent flushing of the slurry pits. In this study, dosages of additives such as sodium dodecyl sulfate (SDS) and hydrogen peroxide (H 2 O 2 ) were optimized to achieve reduction in CH 4 emissions from residual pig slurry during storage. In addition, the effects on emissions when both the treatments were combined and the effects of SDS treatment on slurry acidified with sulfuric acid (H 2 SO 4 ) were studied in order to reduce CH 4 and ammonia (NH 3 ) emissions from residual pig slurry storage. A maximum of 98% and 70% reduction in CH 4 emissions were achieved with SDS and H 2 O 2 treatments, respectively. The combination of SDS and H 2 O 2 did not increase efficiency in reducing CH 4 emissions compared to SDS treatment alone. Whereas the application of SDS to slurry acidified with H 2 SO 4 (pH 6.2) increased the CH 4 mitigation efficiency by 15-30% compared to treating slurry with only SDS. The combined treatment (SDS + H 2 SO 4 ) reduced NH 3 emissions by 20% compared to treating slurry with H 2 SO 4 (pH 6.2) alone. Hereby, combined treatment (SDS + H 2 SO 4 ) can reduce both CH 4 and NH 3 emissions, with a reduced amount of chemicals required for the treatment. Hence, application of SDS at concentrations <2 g kg -1 to acidified slurry is recommended to treat residual pig manure in pig barns., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

Ant nests can affect the process and seasonal dynamics of forest soil methane emissions through mediating methane oxidation/reduction microorganisms and physicochemical environments. To explore the process and mechanism by which ant nests affect soil methane emissions from Hevea brasiliensis plantation in Xishuangbanna, we measured the seasonal dynamics of methane emissions from ant nest and non-nest soils by using static chamber-gas chromatography method, and analyzed the effect of ant nesting on the changes in functional microbial diversity, microhabitats, and soil nutrients in the plantations. The results showed that: 1) Ant nests significantly affected the mean annual soil methane emissions in tropical plantation. Methane emissions in ant nest were decreased by 59.9% than the non-nest soil. In the dry season, ant nest soil was a methane sink (-1.770 μg·m -2 ·h -1 ), which decreased by 87.2% compared with the non-nest soil, while it was a methane source (0.703 μg·m -2 ·h -1 ) that increased by 152.7% in the wet season. 2) Ant nesting affected methane emissions via changing soil temperature, humidity, carbon and nitrogen concentrations. In contrast to the control, the mean annual temperature, humidity, and carbon and nitrogen content increased by 4.9%-138.5% in ant nest soils, which explained 90.1%, 97.3%, 27.3%-90.0% of the variation in methane emissions, respectively. 3) Ant nesting affected the emission dynamics through changing the diversity and community structure of methane functional microbe. Compared with the control, the average annual methanogen diversity (Ace, Chao1, Shannon, and Simpson indices) in the ant nest ranged from -9.9% to 61.2%, which were higher than those (-8.7%-31.2%) of the methane-oxidising bacterial communities. The relative abundance fluctuations of methanogens and methanotrophic bacteria were 46.76% and -6.33%, respectively. The explaining rate of methanogen diversity to methane emissions (78.4%) was higher than that of oxidizing bacterial diversity (54.5%), the relative abundance explained by the dominant genus of methanogens was 68.9%. 4) The structural equation model showed that methanogen diversity, methanotroph diversity, and soil moisture were the main factors controlling methane emissions, contributing 95.6%, 95.0%, and 91.2% to the variations of emissions, respectively. The contribution (73.1%-87.7%) of soil temperature and carbon and nitrogen components to the emission dynamics was ranked the second. Our results suggest that ant nesting mediates the seasonal dynamics of soil methane emissions, primarily through changing the diversity of methane-function microorganisms and soil water conditions. The research results deepen the understanding of the mechanism of biological regulation of methane emission in tropical forest soil.

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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Mitigation of methane emission, a potent greenhouse gas, is a worldwide priority to limit global warming. A substantial part of anthropogenic methane is emitted by the livestock sector, as methane is a normal product of ruminant digestion. We present the latest developments and challenges ahead of the main efficient mitigation strategies of enteric methane production in ruminants. Numerous mitigation strategies have been developed in the last decades, from dietary manipulation and breeding to targeting of methanogens, the microbes that produce methane. The most recent advances focus on specific inhibition of key enzymes involved in methanogenesis. But these inhibitors, although efficient, are not affordable and not adapted to the extensive farming systems prevalent in low- and middle-income countries. Effective global mitigation of methane emissions from livestock should be based not only on scientific progress but also on the feasibility and accessibility of mitigation strategies.

Biogas digestive effluent (BDE) has been applied to rice fields in the Vietnamese Mekong Delta (VMD). However, limited information is available on the community composition and isolation of methanotrophs in these fields. Therefore, the present study aimed (i) to clarify the responses of the methanotrophic community in paddy fields fertilized with BDE or synthetic fertilizer (SF) and (ii) to isolate methanotrophs from these fields. Methanotrophic communities were detected in rhizospheric soil at the rice ripening stage throughout 2 cropping seasons, winter-spring (dry) and summer-autumn (wet). Methanotrophs were isolated from dry-season soil samples. Although the continued application of BDE markedly reduced net methane oxidation potential and the copy number of pmoA genes, a dissimilarity ordination ana-lysis revealed no significant difference in the methanotrophic community between BDE and SF fields (P=0.167). Eleven methanotrophic genera were identified in the methanotrophic community, and Methylosinus and Methylomicrobium were the most abundant, accounting for 32.3-36.7 and 45.7-47.3%, respectively. Type-I methanotrophs (69.4-73.7%) were more abundant than type-II methanotrophs (26.3-30.6%). Six methanotrophic strains belonging to 3 genera were successfully isolated, which included type I (Methylococcus sp. strain BE1 and Methylococcus sp. strain SF3) and type II (Methylocystis sp. strain BE2, Methylosinus sp. strain SF1, Methylosinus sp. strain SF2, and Methylosinus sp. strain SF4). This is the first study to examine the methanotrophic community structure in and isolate several methanotrophic strains from BDE-fertilized fields in VMD.

This study proposed a method for measuring the methane (CH 4 )/carbon dioxide (CO 2 ) ratio from individual beef cattle under on-farm conditions and estimated the variance components of the CH 4 /CO 2 ratio. Gas measurements were conducted using 166 Japanese Black cattle group-housed in pens equipped with individual feed bins. The gas containing the animal's breath was measured individually after concentrate feeding by covering the feed bin with a sheet with sampling inlets. Measurements were performed six times (three consecutive days, twice daily) per individual. Most of the sampled gas contained more than 1000 ppm of the mean background-corrected CO 2 , suggesting that the method proposed in this study successfully collected sufficient breath concentration to accurately measure the CH 4 /CO 2 ratio. The between-animal variance accounted for 31.7% of the total variance in the CH 4 /CO 2 ratio. The results showed that the gas collection method proposed in this study could be a useful tool for measuring the CH 4 /CO 2 ratio under on-farm conditions. The variance component obtained from this study will help to establish protocols for generating data for genetic evaluation and performing dietary experiments with sufficient statistical power., (© 2024 Japanese Society of Animal Science.)

Septic tanks in low- and middle-income countries are often not emptied for a long time, potentially resulting in poor pollutant removal efficiency and increased greenhouse gas emissions, including methane (CH 4 ). We examined the impact of long emptying intervals (4.0-23 years) on the biochemical oxygen demand (BOD) removal efficiency of 15 blackwater septic tanks and the CH 4 emission rates of 23 blackwater septic tanks in Hanoi. The average BOD removal efficiency was 37% (-2-65%), and the average CH 4 emission rate was 10.9 (2.2-26.8) g/(cap·d). The emptying intervals were strongly negatively correlated with BOD removal efficiency ( R = -0.676, p = 0.006) and positively correlated with CH 4 emission rates ( R = 0.614, p = 0.001). CH 4 emission rates were positively correlated with sludge depth ( R = 0.596, p = 0.002), but against expectation, negatively correlated with BOD removal efficiency ( R = -0.219, p = 0.451). These results suggest that shortening the emptying interval improves the BOD removal efficiency and reduces the CH 4 emission rate. Moreover, the CH 4 emission estimation of the Intergovernmental Panel on Climate Change, which is a positive conversion of BOD removal, might be inaccurate for septic tanks with long emptying intervals. Our findings suggest that emptying intervals, sludge depth, and per-capita emission factors reflecting long emptying intervals are potential parameters for accurately estimating CH 4 emissions from septic tanks.

As an important source of atmospheric methane, methane emissions from coastal wetlands are affected by many factors. However, the methane emission process and interrelated coupling mechanisms in coastal wetland soils of a variety of environments remain unclear owing to complex interactions between intensified anthropogenic activities and climate change in recent years. In this study, we investigated methane cycling processes and the response mechanisms of environmental and microbial factors in soils at different depths under four typical coastal wetland vegetation types of the Yellow River Delta, China, using laboratory culture and molecular biology techniques. Our results show that methane generation pathways differed among the different soil layers, and that the methane emission process has a special response to soil N compounds (NO 3 - ). We found that nitrogen can indirectly affect methane emission by impacting key physicochemical properties (pH, oxidation reduction potential, etc.) and some functional communities (mcrA, ANME-2d, sulfate-reducing bacteria (SRB), narG, nosZII). Methane production processes in shallow soils compete closely with sulfate reduction processes, while methane emissions facilitated in deeper soils due to denitrification processes. We believe that our results provide a reference for future research and wetland management practices that seek to mitigate the global greenhouse effect and climate change.4 + ). We found that nitrogen can indirectly affect methane emission by impacting key physicochemical properties (pH, oxidation reduction potential, etc.) and some functional communities (mcrA, ANME-2d, sulfate-reducing bacteria (SRB), narG, nosZII). Methane production processes in shallow soils compete closely with sulfate reduction processes, while methane emissions facilitated in deeper soils due to denitrification processes. We believe that our results provide a reference for future research and wetland management practices that seek to mitigate the global greenhouse effect and climate change., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Rice paddy is a significant source of atmospheric methane (CH 4 ), a major global warming source. CH 4 emission from paddy fields is greatly influenced by phosphorus (P) management, especially the long-term non-P application on CH 4 emission is largely unexplored. In the present study, long-term non-P application (NK) and P application (NPK) treatments of two paddy fields in Suzhou (from 1980) and Yixing (from 2009), Tai Lake region was done. The effect of P application on CH 4 emissions and related microorganisms (i.e., methanogens and methanotrophs) from 2019 to 2020 was analyzed. Results revealed that long-term NK treatment didn't alter the seasonal trend of CH 4 flux, but significantly promoted CH 4 emissions at the tillering stage. The non-P application for >12 years caused the cumulative CH 4 emissions of NK treatment in the whole rice season significantly increased by 41.9-221 % in two fields compared to NPK treatment in 2019 and 2020. NK treatment increased the abundance and diversity of methanogens, while reducing the abundance and diversity of methanotrophs. Community composition of soil pmoA gene differed in two experiment sites. Correlation analysis revealed that the CH 4 emission was significant and positively related to soil mcrA gene and C/P while negatively related to soil pmoA gene and P. Structure equation model analysis show the low soil available P content was the dominant driving factor for the high CH 4 emission under long-term non-P application through its direct impact on soil mcrA and pmoA genes. The increased soil organic acid content was another driver which was positively related to soil mcrA gene and negatively to soil pmoA gene. Our findings demonstrate the important role of soil P in regulating CH 4 emissions from paddy fields in the Tai Lake region, China, and suitable P application is necessary for ensuring the yield while reducing CH 4 emission., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

China has shut down and abandoned a substantial number of coal mines since 1999, which have been releasing methane (CH 4 ) for many years. However, the characteristics of China's abandoned mine methane (AMM) emissions are still unclear; this is a concerning knowledge gap because coal mines are the largest contributor to China's anthropogenic CH 4 emissions. This study used two methods to estimate China's historical AMM emissions over the past 40 years (1980-2020) and to project its AMM emissions to 2060 which is the target year for China's carbon neutrality goal. The results show that China's AMM emissions increased substantially from 0.11 ± 0.03 million tons per year (Mt/yr) (3.1 ± 0.84 Mt/yr CO 2 -eq) in 1980 to 4.7 ± 0.94 Mt/yr (131 ± 26 Mt/yr CO 2 -eq) in 2020. An accelerated growth rate was found during 1998-2005, with AMM emissions rapidly increasing by approximately three times, which was consistent with the high number of mine shutdowns. In 2019, we found that AMM emissions had become the fourth largest anthropogenic source in China, higher than the national anthropogenic CH 4 emissions of individual United Nations Framework Convention on Climate Change Annex I countries excluding the United States of America and the Russian Federation. If unabated, China's AMM emissions are projected to peak at 8.7 ± 2.6 Mt/yr in 2040 and reach approximately one-third of China's anthropogenic carbon dioxide emissions in 2060. This study reveals that understanding AMM emissions can help more accurately quantify China's total CH 4 emissions and guide their future mitigation., (Copyright © 2022 Elsevier Inc. All rights reserved.)

This study determined the effect of purified condensed tannin inclusion levels in a diet on production, haematological indices, blood biochemical components, meat quality and methane emission by yearling indigenous male Bapedi sheep on a grass hay and sheep pellet-based diet in a 28-day trial. The diets contained similar (P > 0.05) nutrients but with different (P < 0.05) purified condensed tannin supplementation levels. A complete randomized design was used. Twenty-four yearling male Bapedi sheep were assigned to four dietary treatments having different purified condensed tannin levels of 0 (GH 80 P 20 PCT 0 ), 30 (GH 80 P 20 PCT 30 ), 40 (GH 80 P 20 PCT 40 ) and 50 (GH 80 P 20 PCT 50 ) g/kg DM. A quadratic type of equation was also used to determine condensed tannin supplementation levels for optimal performance and methane emission reduction by sheep. Supplementing diets with purified condensed tannins did not affect (P > 0.05) diet intake, digestibility and live weight gain of male Bapedi sheep. Supplementing diets with purified condensed tannins did not affect (P > 0.05) blood components of male Bapedi sheep. Inclusion of condensed tannins in the diets did not affect (P > 0.05) Bapedi sheep meat pH and sensory attributes. However, supplementing diets with purified condensed tannins decreased (P < 0.05) methane emission by 51 to 60%. A 49.08 g supplementation level with purified condensed tannins per kg DM diet was calculated, with the use of quadratic equations, to result in the lowest methane emission by male Bapedi sheep. The meat of male Bapedi rams on diets containing 30, 40 or 50 g of purified condensed tannins per kg DM contained higher (P < 0.05) antioxidant activities than those from rams fed a diet without purified condensed tannins. These results indicate that purified condensed tannin supplementation levels of 0, 30, 40 or 50 g/kg DM diet had no adverse effects on growth performance, blood profiles and meat sensory attributes of male Bapedi sheep. However, supplementation levels of 30, 40 or 50 g of purified condensed tannins per kg DM diet reduced methane emission by 51 to 60%, and increased sheep meat antioxidant activity values. Supplementing diets with purified condensed tannins has the potential to reduce methane production and emission by sheep. However, long-term studies are recommended to ascertain the present findings., (© 2022. The Author(s).)

The hand-held laser methane detector (LMD) technique has been suggested as an alternative method for measuring methane (CH4) emissions from enteric fermentation of ruminants in the field. This study aimed to establish a standard procedure for using LMD to assess CH4 production in cattle and evaluate the efficacy of the protocol to detect differences in CH4 emissions from cattle fed with diets of different forage-to-concentrate (FC) ratios. Experiment 1 was conducted with four Hanwoo steers (584 ± 57.4 kg body weight [BW]) individually housed in metabolic cages. The LMD was installed on a tripod aimed at the animal's nostril, and the CH4 concentration in the exhaled gas was measured for 6 min every hour for 2 consecutive days. For the data processing, the CH4 concentration peaks were identified by the automatic multi-scale peak detection algorithm. The peaks were then separated into those from respiration and eructation by fitting combinations of two of the four distribution functions (normal, log-normal, gamma, and Weibull) using the mixdist R package. In addition, the most appropriate time and number of consecutive measurements to represent the daily average CH4 concentration were determined. In experiment 2, 30 Hanwoo growing steers (343 ± 24.6 kg BW), blocked by BW, were randomly divided into three groups. Three different diets were provided to each group: high FC ratio (35:65) with low-energy concentrate (HFC-LEC), high FC ratio with high-energy concentrate (HFC-HEC), and low FC ratio (25:75) with high-energy concentrate (LFC-HEC). After 10 d of feeding the diets, the CH4 concentrations for all steers were measured and analyzed in duplicate according to the protocol established in experiment 1. In experiment 1, the mean correlation coefficient between the CH4 concentration from respiration and eructation was highest when a combination of two normal distributions was assumed (r = 0.79). The most appropriate measurement times were as follows: 2 h and 1 h before, and 1 h and 2 h after morning feeding. Compared with LFC-HEC, HFC-LEC showed 49% and 57% higher CH4 concentrations in exhaled gas from respiration and eructation (P < 0.01). In conclusion, the LMD method can be applied to evaluate differences in CH4 emissions in cattle using the protocol established in this study., (© The Author(s) 2022. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Denitrifying anaerobic methane oxidation (DAMO) plays an important role in the element cycle of wetlands. In recent years, the content of antibiotics in wetlands has gradually increased due to human activities. However, the impact of antibiotics on the ecological function of DAMO remains unclear. Here we studied the influence of three high-content quinolone antibiotics (QNs) on DAMO in the sediments of the Baiyangdian Wetland. The results show that QNs can significantly promote the potential DAMO rates. Moreover, the enhancement of potential DAMO rates is positively correlated with the dosage of QNs. This promotion effect of QNs on nitrate-DAMO can be attributed to the hormesis phenomenon or their inhibition of substrate competitors. As antibacterial agents, QNs inhibit nitrite-DAMO conducted by bacteria, but greatly promote nitrate-DAMO conducted by archaea. These results suggest that the short-term effect of QNs on DAMO in wetlands is promotion rather than inhibition., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Mangrove sediments are known sources for methane emission that has a very high global warming potential. The spatio-temporal emission of methane in the mangrove sediments was quantified in the present study using the static closed chamber technique. Besides, the effects of environmental parameters on methane emission were estimated at Betim (mouth), Chorão (midstream), and Volvoi (upstream) stations along the tropical Mandovi estuary. On an average, the methane emission at the upstream estuarine station at Volvoi was maximum (1268.68 ± 176 nM cm -2  h -1 ) compared to the other two stations. Annually, the methane emission was significantly influenced by physicochemical parameters like salinity at Betim and Volvoi and, the redox potential at the midstream station at Chorão. The variation of methane emission between the 3 stations (P < 0.001) is attributed to the variation in methanotrophy (P < 0.05) and methanogenesis (P < 0.05) influenced by differences in the concentration of nutrients (P < 0.05) and organic carbon (P < 0.05). Seasonally, the highest methane emission at Chorão was during the post-monsoon, at Betim was during the monsoon season (1305.34 ± 108.58 nM cm -2  h -1 ), and at the upstream station at Volvoi, the emission of methane was highest during the pre-monsoon season (1514.68 ± 130.94 nM cm -2  h -1 ). The influence of environmental parameters was more prominent on methane emission at the 3 stations during the monsoon season. Spearman's correlation analysis indicated that seasonal changes in methane emission are not only attributed to the influence of seasonal rainfall that leads to the fresh water input, but also to the variation in biogeochemical parameters., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The global methane (CH 4 ) budget is based on a sensitive balance between methanogenesis and CH 4 oxidation (aerobic and anaerobic). The response of these processes to climate warming, however, is not quantified. This largely reflects our lack of knowledge about the temperature sensitivity (Q 10 ) of the anaerobic oxidation of CH 4 (AOM)-a ubiquitous process in soils. Based on a 13 CH 4 labeling experiment, we determined the rate, Q 10 and activation energy of AOM and of methanogenesis in a paddy soil at three temperatures (5, 20, 35°C). The rates of AOM and of methanogenesis increased exponentially with temperature, whereby the AOM rate was significantly lower than methanogenesis. Both the activation energy and Q 10 of AOM dropped significantly from 5-20 to 20-35°C, indicating that AOM is a highly temperature-dependent microbial process. Nonetheless, the Q 10 of AOM and of methanogenesis were similar at 5-35°C, implying a comparable temperature dependence of AOM and methanogenesis in paddy soil. The continuous increase of AOM Q 10 over the 28-day experiment reflects the successive utilization of electron acceptors according to their thermodynamic efficiency. The basic constant for Q 10 of AOM was calculated to be 0.1 units for each 3.2 kJ mol -1 increase of activation energy. We estimate the AOM in paddy soils to consume 2.2~5.5 Tg CH 4 per year on a global scale. Considering these results in conjunction with literature data, the terrestrial AOM in total consumes ~30% of overall CH 4 production. Our data corroborate a similar Q 10 of AOM and methanogenesis. As the rate of AOM in paddy soils is lower than methanogenesis, however, it will not fully compensate for an increased methane production under climate warming., (© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

The methane (CH 4 ) emissions from urban sources are increasing, and they depend on the processes and technologies applied in each one. Thus, studying them individually to quantify their emissions and understand their behavior to design CH 4 mitigation strategies is meaningful. Although many studies have been carried out in different cities worldwide, the complex methodologies and technologies applied are not readily available in developing countries. The main objective of this work is to apply a simple and inexpensive methodology to collect air samples in urban areas using syringes with a three-way stopcock. Considering the baseline concentration in different urban zones, the WWTP contribution to atmospheric CH 4 concentration was assessed. Moreover, it was possible to estimate the CH 4 emission rate from the source by applying the inverse Gaussian model. The atmospheric CH 4 concentrations inside and around the WWTP varied from 2.04 to 32.78 ppm. Most of the highest concentrations were found inside the WWTP; however, high concentrations were found up to 500 m from its center. The values in the urban zones were between 2.06 and 3.52 ppm, consistently higher in the area with the highest population density. Finally, considering the WWTP as a single source and according to the operational and atmospheric conditions during the studied period, the mean CH 4 emission rate from this source was 2.08E + 04 μg s -1 . The proposed sampling methodology could be applied to estimate CH 4 emission rates from fixed sources in areas with overlapping sources., (© 2021. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

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., (Crown Copyright © 2021. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. All rights reserved.)

Dietary strategies aiming at minimizing enteric methane (CH 4 ) emission in ruminants are of practical interest from nutritional, economical, and environmental point of view. The present study evaluated the effects of supplementing Leucaena leucocephala leaves either alone or in conjunction with malic acid on nutrient utilization, growth performance, and enteric CH 4 emission in crossbred cattle fed wheat straw and concentrate-based diet under tropical conditions. Eighteen crossbred (Karan-Fries) calves were randomly allocated into 3 groups: G-I (control)-fed wheat (Triticum aestivum) straw and concentrate mixture in the ratio 50:50; G-II-fed wheat straw, concentrate mixture, and Leucaena leucocephala leaves in the ratio 45:45:10; and (3) G-III-fed similar diet like G-II with an additional supplementation of 1% malic acid on dry matter intake basis. Experimental feeding spanning 90 days included a 7-day metabolism trial and CH 4 quantification study by sulfur hexafluoride tracer technique. Results revealed no significant effect of dietary treatments on dry matter intake (DMI) and digestibility of nutrients, except neutral detergent fiber (NDF) digestibility which was 5.5% higher (P < 0.05) in G-III as compared to control. Further, nitrogen (N) metabolism, rumen microbial protein synthesis, and growth performance remained similar among the treatments. No significant effect was also observed for enteric CH 4 emission (expressed as g/day and g/kg DMI) in calves supplemented with Leucaena leucocephala leaves and malic acid. Therefore, the present findings depict modest improvement in fiber digestibility with no encouraging effect in mitigating enteric CH 4 in growing cattle calves by supplementing Leucaena leucocephala leaves alone or with malic acid within the selected levels., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

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., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Background: Lactating dairy cows are the greatest livestock contributor of methane, a major global greenhouse gas (GHG). However, good feeding management with adequate mineral intake can offers an effective approach to maintaining high levels of milk production and the health of dairy cows over the entire course of lactation, while also helping to reduce methane emission. The study described here investigated the plasma concentrations of both macroelements (Ca, Na, K, Mg, P) and microelements (Zn, Cu, Fe, Mn), as well as enteric methane emission and milk composition in high-yielding dairy cows in different lactation periods. The experiment was performed on Holstein-Friesian dairy cows with the average milk yield of 41 (± 9) L/day in a Polish commercial farm with modern dairy systems. A total of thirty high-yielding dairy cows were randomly assigned into three groups differing by lactation stage: early stage (Early, days 25-100), middle stage (Middle, days 101-250), and late stage (Late, day 250 and later). Dietary treatment for all cows was a total mixture ration (TMR) with maize and alfalfa silage the main forage components., Results: The greatest milk yield and methane production were recorded in early-stage lactating cows, but the greatest methane intensity per kg of corrected milk was recorded in the late stage of lactation. Plasma concentrations of macroelements and microelements did not differ by lactation stages, but increased plasma concentrations of Zn and Fe and decreased plasma levels of Mg were noted during lactation. A positive correlation was found between plasma levels of Mg and other macroelements (Ca, Na, K), and between the concentrations of Fe and Zn, P in plasma, but no correlation between methane emission and mineral status was detected in the different lactation stages., Conclusions: Our results showed different mineral requirements and enteric methane emissions in each lactation stage. The feeding strategy and mineral utilization were adequate to maintain the health, mineral status, and milk production of the Holstein cows during the entire lactation period, and suggest an effective way of reducing methane emission., (© 2021. The Author(s).)

Petroleum-contaminated soil is considered among the most important potential anthropogenic atmospheric methane sources. Additionally, various rhizoremediation factors can affect methane emissions by altering soil ecosystem carbon cycles. Nonetheless, greenhouse gas emissions from soil have not been given due importance as a potentially relevant parameter in rhizoremediation techniques. Therefore, in this study we sought to investigate the effects of different plant and soil amendments on both remediation efficiencies and methane emission characteristics in dieselcontaminated soil. An indoor pot experiment consisting of three plant treatments (control, maize, tall fescue) and two soil amendments (chemical nutrient, compost) was performed for 95 days. Total petroleum hydrocarbon (TPH) removal efficiency, dehydrogenase activity, and alkB ( i.e. , an alkane compound-degrading enzyme) gene abundance were the highest in the tall fescue and maize soil system amended with compost. Compost addition enhanced both the overall remediation efficiencies, as well as pmoA ( i.e. , a methane-oxidizing enzyme) gene abundance in soils. Moreover, the potential methane emission of diesel-contaminated soil was relatively low when maize was introduced to the soil system. After microbial community analysis, various TPH-degrading microorganisms ( Nocardioides, Marinobacter, Immitisolibacter, Acinetobacter, Kocuria, Mycobacterium, Pseudomonas, Alcanivorax ) and methane-oxidizing microorganisms ( Methylocapsa, Methylosarcina ) were observed in the rhizosphere soil. The effects of major rhizoremediation factors on soil remediation efficiency and greenhouse gas emissions discussed herein are expected to contribute to the development of sustainable biological remediation technologies in response to global climate change.

Background: Information about the nutritive value, dry matter (DM) digestibility, and methane (CH 4 ) emission potential of grass species is required for their optimal utilization in ruminant rations. The present study was designed: (i) to quantify the nutrient profile, mineral composition and in vitro dry matter digestibility (IVDMD) of winter grass species commonly available in northern Pakistan; and (ii) to measure the in vitro gas production (IVGP) and CH 4 emission of the grass species during 72 h in vitro ruminal fermentation. Seven grass species, namely, Cenchrus ciliaris, Setaria anceps, Panicum antidotale, P. maximum, Pennisetum purpureum, Pennisetum orientale, and Atriplex lentiformis were assessed., Results: A high level of variability (P < 0.001) was observed among grass species for the content of all measured nutrients, IVDMD, IVGP, and CH 4 -production. Notably, the content (g kg -1 DM) of crude protein varied from 59.8 to 143.3, neutral detergent fiber from 560.3 to 717.9, IVDMD from 375.1 to 576.2, and 72 h cumulative IVGP from 97.6 to 227.4 mL g -1 organic matter (OM) and CH 4 from 48 to 67 mL g -1 OM. Among the grasses, P. antidotale had greater content (g kg -1 DM) of crude protein (CP) (143.3), IVDMD (576.2), and 72 h cumulative IVGP (227.4 mL g -1 OM), and produced the smallest amount of total CH 4 (48 mL g -1 OM) during 72 h fermentation. In contrast, A. lentiformis had the lowest content (g kg -1 DM) of CP (59.8), IVDMD (375.1), 72 h cumulative IVGP (97.6 mL g -1 OM), and produced a greater amount of total CH 4 (67 mL g -1 OM) during 72 h fermentation., Conclusion: The findings of the current study highlight that it is possible to select and further develop grass species with high nutritional value and lower CH 4 -production, which can improve livestock productivity, farm profitability, and long-term environment sustainability. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

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., (Copyright © 2021 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

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., (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

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., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

To develop an economic and sustainable biochar application strategy for mitigating methane emission from paddy fields, a four-year field experiment was conducted to compare two biochar amendment methods. The annual low (AL) rate pyrolyzed biochar returning method used the same amount of biochar as was harvested from rice straw in the field, 2.8 t ha -1  yr -1 . The high single (HS) biochar returning method consisted of a single application of 22.5 t ha -1 biochar only in the first year, 2015. Our results showed that the AL biochar returning strategy prevailed over the HS strategy in mitigating methane emission from paddy fields. On average, AL and HS could reduce methane emissions by 41% and 38.25% in four years, respectively. Methane accumulation per unit rice production was 45.8% and 43.1% in AL and HS, respectively. AL showed a stable effect on mitigating methane emission over four successive years, which resulted from the continuously increasing methanotrophs due to annual fresh biochar application. Aged biochar weakened the promotion of methanotrophs, leading to lower methane reduction rates in HS than in AL in the 4 years. Our results indicate that AL is a highly sustainable strategy for methane mitigation in paddy fields due to its high efficiency, practical operation, and economical acceptance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Methane emission by ruminants has contributed considerably to the global warming and understanding the genomic architecture of methane production may help livestock producers to reduce the methane emission from the livestock production system. The goal of our study was to identify genomic regions affecting the predicted methane emission (PME) from volatile fatty acids (VFAs) indicators and VFA traits using imputed whole-genome sequence data in Iranian Holstein cattle., Results: Based on the significant-association threshold (p < 5 × 10 - 8 ), 33 single nucleotide polymorphisms (SNPs) were detected for PME per kg milk (n = 2), PME per kg fat (n = 14), and valeric acid (n = 17). Besides, 69 genes were identified for valeric acid (n = 18), PME per kg milk (n = 4) and PME per kg fat (n = 47) that were located within 1 Mb of significant SNPs. Based on the gene ontology (GO) term analysis, six promising candidate genes were significantly clustered in organelle organization (GO:0004984, p = 3.9 × 10 - 2 ) for valeric acid, and 17 candidate genes significantly clustered in olfactory receptors activity (GO:0004984, p = 4 × 10 - 10 ) for PME traits. Annotation results revealed 31 quantitative trait loci (QTLs) for milk yield and its components, body weight, and residual feed intake within 1 Mb of significant SNPs., Conclusions: Our results identified 33 SNPs associated with PME and valeric acid traits, as well as 17 olfactory receptors activity genes for PME traits related to feed intake and preference. Identified SNPs were close to 31 QTLs for milk yield and its components, body weight, and residual feed intake traits. In addition, these traits had high correlations with PME trait. Overall, our findings suggest that marker-assisted and genomic selection could be used to improve the difficult and expensive-to-measure phenotypes such as PME. Moreover, prediction of methane emission by VFA indicators could be useful for increasing the size of reference population required in genome-wide association studies and genomic selection.

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., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Achieving high animal productivity without degrading the environment is the primary target in pasture-based dairy farming. This study investigated the effects of changing the forage base in spring from grass-clover pastures to forb or legume-based pastures on milk yield, N utilization, and methane emissions of Jersey cows in Western Oregon. Twenty-seven mid-lactation dairy cows were randomly assigned to one of three pasture treatments: grass-clover-based pasture composed of festulolium, tall fescue, orchardgrass, and white clover (Grass); forb-based pasture composed of chicory, plantain, and white clover (Forb); and legume-based pasture composed of red clover, bird's-foot trefoil, berseem clover, and balansa clover (Legume). Pastures were arranged in a randomized complete block design with three replicates (i.e., blocks) with each replicate grazed by a group of three cows. Production and nutritive quality of the forages, animal performance, milk components, nitrogen partitioning, and methane emissions were measured. Feed quality and dry matter intake (DMI) of cows were greater (P ≤ 0.05) for Legume and Forb vs. Grass, with consequent greater milk and milk solids yields (P < 0.01). Cows grazing Forb also had more (P < 0.01) lactose and linoleic acid in milk compared with cows grazing the other pastures, and less (P = 0.04) somatic cell counts compared with Grass. Cows grazing Forb had substantially less (P < 0.01) N in urine, milk, and blood compared with cows grazing the other pastures, with not only a greater (P < 0.01) efficiency of N utilization for milk synthesis calculated using milk urea nitrogen but also a larger (P < 0.01) fecal N content, indicating a shift of N from urine to feces. Both Forb and Legume had a diuretic effect on cows, as indicated by the lower (P < 0.01) creatinine concentration in urine compared with Grass. Methane emissions tended to be less (P = 0.07) in cows grazed on Forb vs. the other pastures. The results indicate that Forb pasture can support animal performance, milk quality, and health comparable to Legume pasture; however, Forb pasture provides the additional benefit of reduced environmental impact of pasture-based dairy production., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Aquaculture practices are steadily increasing to meet the fish demand, especially in tropical countries like India. However, efforts to characterize the contribution of these aquaculture ponds towards greenhouse gas emission like CH 4 are still very few. CH 4 concentration in water [pCH 4 (water)] and air-water CH 4 fluxes were estimated (during the summer months) in two sewage-fed ponds having different depths situated in the East Kolkata Wetlands, India (a Ramsar site). pCH 4 (water) in both of these ponds showed significant positive correlation with water temperature (R 2  = 0.68 and 0.71, p < 0.05). Daily mean chlorophyll-a, turbidity, biochemical oxygen demand (BOD) and gross primary productivity (GPP) also showed positive correlation with pCH 4 (water). This indicated that higher primary production and presence of turbid materials acted as substrates for methanogenesis, which favoured air-water CH 4 effluxes towards atmosphere. Mean air-water CH 4 fluxes in the ponds having depth of 1.1 m and 0.6 m were observed to be 24.79 ± 12.02 mg m -2  h -1 and 6.05 ± 3.14 mg m -2  h -1 respectively. Higher depth facilitated net heterotrophic conditions, which led to lower dissolved oxygen levels, which, in turn, led to lower rate of CH 4 oxidation. Moreover, under reduced photosynthetically active radiation (in the pond having greater depth), the pH values were comparatively lower (~7.7), which further facilitated a favourable condition for the methanogens to grow. On the whole, it was inferred that apart from pre-established physicochemical factors, depth was also found to play a decisive role in regulating the air-water CH 4 fluxes from these aquaculture ponds. In future, continuous sampling should be carried out (by chamber method) to take into account the ebullition CH 4 fluxes, and more number of ponds should be sampled throughout a complete annual cycle to have a more holistic understanding about this cluster of sewage-fed aquaculture ponds.

A field experiment in Yangtze River delta of China was conducted to investigate the effects of four treatments (conventional chemical fertilizers (CF), chemical fertilizers incorporated with wheat straw (CF-WS), slow-release urea fertilizer incorporated with wheat straw (SCF-WS), and no fertilizers (Non-F)) on methane emission, rice grain yield, and straw biomass in three (2013, 2014, and 2015) consecutive growing seasons. Similar air temperature and precipitation were recorded in 2014 and 2015 normal seasons; however, the 2013 season with a 2.1-2.3 °C higher mean air temperature and a 61-64% lower precipitation than the normal seasons was considered as a warm-and-dry season.No significant differences in seasonal total methane emissions across all treatments were observed in 2014 and 2015 seasons. Seasonal total methane emissions were 58-294% higher in 2013 season compared to 2014 and 2015 seasons, which suggests that higher ambient temperatures increase methane emissions from paddy fields. The enhanced methane emission was seen mainly during the mid-to-late growth stages after mid-season drainage. CF-WS and SCF-WS significantly increased methane emissions before mid-season drainage relative to CF, and thereby enhanced methane emissions in both normal and warm-and-dry seasons in a seasonal scale.While rice grain yield in each treatment in 2013 season was close to or lower than that in 2014 and 2015 seasons, straw biomass in CF, CF-WS, and SCF-WS in 2013 season were significantly higher than those in 2014 and 2015 seasons, by both 29%, 33-41%, and 15-16%, respectively. Enhancements in methane emissions at higher air temperatures were significantly correlated to its greater straw biomass. Furthermore, combination of slow-release urea fertilizer and straw by ploughing can significantly increase above-ground biomass yields and nitrogen use efficiency in both normal and warm-and-dry seasons.

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Mitigation of greenhouse gas emissions is relevant for reducing the environmental impact of ruminant production. In this study, the rumen microbiome from Holstein cows was characterized through a combination of 16S rRNA gene and shotgun metagenomic sequencing. Methane production (CH 4 ) and dry matter intake (DMI) were individually measured over 4-6 weeks to calculate the CH 4 yield (CH 4 y = CH 4 /DMI) per cow. We implemented a combination of clustering, multivariate and mixed model analyses to identify a set of operational taxonomic unit (OTU) jointly associated with CH 4 y and the structure of ruminal microbial communities. Three ruminotype clusters (R1, R2 and R3) were identified, and R2 was associated with higher CH 4 y. The taxonomic composition on R2 had lower abundance of Succinivibrionaceae and Methanosphaera, and higher abundance of Ruminococcaceae, Christensenellaceae and Lachnospiraceae. Metagenomic data confirmed the lower abundance of Succinivibrionaceae and Methanosphaera in R2 and identified genera (Fibrobacter and unclassified Bacteroidales) not highlighted by metataxonomic analysis. In addition, the functional metagenomic analysis revealed that samples classified in cluster R2 were overrepresented by genes coding for KEGG modules associated with methanogenesis, including a significant relative abundance of the methyl-coenzyme M reductase enzyme. Based on the cluster assignment, we applied a sparse partial least-squares discriminant analysis at the taxonomic and functional levels. In addition, we implemented a sPLS regression model using the phenotypic variation of CH 4 y. By combining these two approaches, we identified 86 discriminant bacterial OTUs, notably including families linked to CH 4 emission such as Succinivibrionaceae, Ruminococcaceae, Christensenellaceae, Lachnospiraceae and Rikenellaceae. These selected OTUs explained 24% of the CH 4 y phenotypic variance, whereas the host genome contribution was ~14%. In summary, we identified rumen microbial biomarkers associated with the methane production of dairy cows; these biomarkers could be used for targeted methane-reduction selection programmes in the dairy cattle industry provided they are heritable., (© 2019 The Authors. Journal of Animal Breeding and Genetics published by Blackwell Verlag GmbH.)

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 (R 2 = 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., (The Authors. Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

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., (Published by FASS Inc. and Elsevier Inc. on behalf of the American Dairy Science Association®. All rights reserved.)

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., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Lonicera japonica (LJ; honeysuckle) is used in traditional folk medicine in Korea and is a rich source of ascorbic acid and phenolic components that are reported to have antioxidant and antibiotic properties. We performed an in vitro experiment to assess the effects of LJ extracts (LJE) on ruminal fermentation. Timothy hay (0.3 g dry matter [DM]) was incubated with buffer, ruminal fluid, and 0%, 3%, 5%, 7%, and 9% LJE. Batch culture fermentation was conducted separately for 12, 24, and 48 hr to determine gas production (GP), ruminal fermentation characteristics, and microbial population characteristics. The effects on GP were generally similar to those on DM degradability, with a linear decrease observed at 9% extract at 24 hr. NH 3 -N showed a linear increase with increasing extract concentrations at 12 hr, whereas a decrease was observed at 24 hr. Extract supplementation decreased methane (CH 4 ) production at 12, 24, and 48 hr. In addition, the abundance of fibrolytic bacteria and ciliate-associated methanogen was reduced at all concentrations of extracts. These results indicate that LJE have the potential to serve as a ruminal fermentation modifier to suppress CH 4 production with minimal effects on nutrient digestion in the rumen., (© 2019 Japanese Society of Animal Science.)

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., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

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., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Carbon sources are a critical requirement for the proliferation of algae and the occurrence of harmful algal blooms (HABs), but are often turned into methane (CH 4 ) after the collapse of severe HABs. Here, we attempt to remove HABs, reduce algal-derived CH 4 emissions, and repair the broken carbon biogeochemical cycle in aquatic systems using an integrated ecological approach including flocculation, capping, and submerged macrophyte induction, preliminary at a microcosm scale. This strategy sustainably reached 98% algal removal after 65 days of incubation and resulted in an aerobic microenvironment (ORP = +12 mv) at the sediment-water interface. The approach contributed to an approximate 60% decline in CH 4 released from the aquatic environment into the atmosphere jointly through assimilation of mineralized organic carbon by submerged macrophytes, production of carbon dioxide (CO 2 ) under aerobic conditions, and aerobic CH 4 oxidation. Some of the CO 2 produced in the aquatic phase contributed to inorganic carbon and formed the submerged macrophytes biomass. A combination of flocculation, capping, and submerged macrophyte incubation were significant contributors to altering the carbon budget and sealing nearly 99% of the carbon in the simulated ecosystem (the majority in sediment, followed by submerged macrophytes), providing a sustainable way to reuse algal-derived carbon and reduce CH 4 emissions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Nitrates have been fed to ruminants, including dairy cows, as an electron sink to mitigate CH 4 emissions. In the NO 3 - reduction process, NO 2 - can accumulate, which could directly inhibit methanogens and possibly other microbes in the rumen. Saccharomyces cerevisiae yeast was hypothesized to decrease NO 2 - through direct reduction or indirectly by stimulating the bacterium Selenomonas ruminantium, which is among the ruminal bacteria most well characterized to reduce both NO 3 - and NO 2 - . Ruminal fluid was incubated in continuous cultures fed diets without or with NaNO 3 (1.5% of diet dry matter; i.e., 1.09% NO 3 - ) and without or with live yeast culture (LYC) fed at a recommended 0.010 g/d (scaled from cattle to fermentor intakes) in a 2 × 2 factorial arrangement of treatments. Treatments with LYC had increased NDF digestibility and acetate:propionate by increasing acetate molar proportion but tended to decrease total VFA production. The main effect of NO 3 - increased acetate:propionate by increasing acetate molar proportion; NO 3 - also decreased molar proportions of isobutyrate and butyrate. Both NO 3 - decreased methane emissions in continuous cultures; however, contrary to expectations, LYC did not attenuate NO 3 - decreased valerate molar proportion only when no LYC was added. Nitrate decreased daily CH 4 emissions by 29%. However, treatment × time interactions were present for both CH 4 and H 2 emission from the headspace; CH 4 was decreased by the main effect of NO 3 - until 6 h postfeeding, but NO 3 - and LYC decreased H 2 emission up to 4 h postfeeding. As expected, NO 3 - decreased methane emissions in continuous cultures; however, contrary to expectations, LYC did not attenuate NO 2 - accumulation., (Copyright © 2019 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Methane (CH 4 ) is predominantly produced in lowland rice soil, but its emission from soil to atmosphere primarily depends on passage/conduit or capillary pore spaces present in rice plants. The gas transport mechanism through aerenchyma pore spaces of rice cultivars was studied to explore the plant mediated CH 4 emission. Seven rice cultivars, based on the life cycle duration (LCD), were tested in tropical eastern India. Three LCD groups were, (a) Kalinga 1 and CR Dhan 204 (LCD: 110-120 days); (b) Lalat, Pooja and CR 1014 (LCD: 130-150 days); and (c) Durga and Varshadhan (LCD: 160-170 days). Rate of CH 4 emission, root exudates, root oxidase activities and shoot aerenchyma pore spaces were analyzed to study the mechanism of plant mediated emission from rice. Aerenchyma pore space was quantified in the hypothesis that it regulates the CH 4 transportation from soil to atmosphere. The ratio of pore space area to total space was lowest in Kalinga 1 cultivar (0.29) and highest was in Varshadhan (0.43). Significant variations in the methane emission were observed among the cultivars with an average emission rate ranged from 0.86 mg m -2  h -1 to 4.96 mg m -2  h -1 . The CH4 emission rates were lowest in short duration cultivars followed by medium and long duration ones. The greenhouse gas intensity considering average CH 4 emission rate per unit grain yield was also lowest (0.35) in Kalinga 1 and relatively less in short and medium duration cultivars. Root exudation was higher at panicle initiation (PI) than maximum tillering (MT) stage. Lowest exudation was noticed in (197.2 mg C plant -1  day -1 ) Kalinga 1 and highest in Varsadhan (231.7 mg C plant -1  day -1 ). So we can say, the rate of CH 4 emission was controlled by aerenchyma orientation, root exudation and biomass production rate which are the key specific traits of a cultivar. Identified traits were closely associated with duration and adaptability to cultivars grown in specific ecology. Therefore, there is possibility to breed rice cultivars depending on ecology, duration and having less CH 4 emission potential, which could be effectively used in greenhouse gas mitigation strategies., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Rising rate of MSW generation and unscientific disposal in the open dumping sites are responsible for emission of high concentrations of methane in developing countries. IPCC Default method (DM), First-order decay (FOD) and LandGEM were used to estimate methane emissions from the unengineered landfill sites of Delhi-Okhla, Bhalswa and Ghazipur between 1984 and 2015. During the period, the total CH 4 emissions was found to be 1288.99, 311.18, 779.32 Gg from the 3 landfill sites of Delhi as predicted by DM, FOD and LandGEM respectively. The energy generation potential from methane for the year 2015 was found to vary from 4.16 × 10 8 to 9.86 × 10 8  MJ for Ghazipur, 2.08 × 10 8 to 4.06 × 10 8  MJ for Okhla and 3.42 × 10 8 to 8.11 × 10 8  MJ for Bhalswa. Efficient utilization of methane from the landfills as an energy source can be a sustainable waste management option., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This study evaluated methane (CH 4 ) emission, intake, digestibility, and nitrogen efficiency in sheep fed diets containing replacement levels (0%, 33%, 50%, and 67% of soybean meal with euglena). In this experiment, four Corriedale wether sheep with an initial body weight of 53.8 ± 4.6 were arranged in a 4 × 4 Latin square design. This experiment lasted 84 days, divided into four experimental periods. Each period lasted 21 days, which consists of 14 days of adaptation to the diets, 5 days to collect samples, and 2 days to collect gas emission from sheep. Methane emission expressed as L/kg DM intake or g/kg DM intake reduced by up to 37% and the energy loss via CH 4 (% of GE intake) reduced by up to 34%. No differences (p > 0.05) were observed in DM and OM intake and whole tract apparent DM digestibility due to substitution of soybean meal with euglena. The total CP loss reduced significantly (linear, p < 0.001) and CP efficiency increased linearly (p = 0.03) with increasing concentration of euglena. As a result, nitrogen balance and average daily weight gain remained unchanged despite higher nitrogen concentration in soybean supplemented group. In conclusion, substitution of soybean meal with euglena reduced methane emission without affecting the performance of animals., (© 2018 The Authors. Animal Science Journal published by John Wiley & Sons Australia, Ltd on behalf of Japanese Society of Animal Science.)