Mitigation Of Methane Emissions Research Articles

Mitigating methane emission from oil sands tailings using enzymatic and lime treatments

Engineering strategies to reduce greenhouse gases (GHGs) emissions by inhibiting methanogenesis in oil sands tailings have rarely been examined. In this study, we explored the potential impact of chemical treatment (lime) and biological treatment using enzymes (lysozyme and protease) on inhibiting methane emissions from tailings. Overall, treatment with protease 3%, lysozyme 3%, and lime 5000 ppm reduced CH4 production (by 52%, 28%, and 25%, respectively) and were weakly associated with the archaeal abundance. Enzymes treatment resulted in a higher reduction in CH4 production compared with lime treatment. A 3% lysozyme treatment suppressed CH4 production (the change in methane was 0.48 mmol) and reduced the degradation of hexane throughout the experiment. Similarly, 3% protease suppressed CH4 production throughout the experiment (the change in methane was 0.78 mmol), which could be attributed to the pH reduction to pH 4.9 at week 23 resulting from the formation of volatile fatty acids. Another possible mechanism could be the formation of toxic compounds, such as high nitrogen content, after protease treatment that inhibited the microbial community. The toxicity effect to Vibrio fischeri was greater with lysozyme 3% and protease 3% treatment than with lime treatment (124 TU and 76 TU, respectively). Lime treatment resulted in the highest reduction in 16S rRNA gene copies from 5.7 × 106 cells g−1 (control) to 2.7 × 105, 1.71 × 105, and 1.4 × 105 cells g−1 for 1600, 3500, and 5000 ppm treatments, respectively. This study supports further work to examine and determine the optimum conditions (e.g., enzyme and lime dosages) for CH4 inhibition.

Technological avenues and market mechanisms to accelerate methane and nitrous oxide emissions reductions.

Strategies targeting methane (CH4) and nitrous oxide (N2O) emissions are critical to meeting global climate targets. Existing literature estimates the emissions of these gases from specific sectors, but this knowledge must be synthesized to prioritize and incentivize CH4 and N2O mitigation. Accordingly, we review emissions sources and mitigation strategies in all key sectors (fuel extraction and combustion, landfilling, agriculture, wastewater treatment, and chemical industry) and the role of carbon markets in reducing emissions. The most accessible reduction opportunities are in the hydrocarbon extraction and waste sectors, where half (>3 Gt-CO2e/year) of the emissions in these sectors could be mitigated at no net cost. In total, 60% of CH4 emissions can be mitigated at less than $50/t-CO2. Expanding the scope of carbon markets to include these emissions could provide cost-effective decarbonization through 2050. We provide recommendations for carbon markets to improve emissions reductions and set prices to appropriately incentivize mitigation.

Differentiating and Mitigating Methane Emissions from Fugitive Leaks from Natural Gas Distribution, Historic Landfills, and Manholes in Montréal, Canada.

Rapidly reducing urban methane (CH4) emissions is a critical component of strategies aimed at limiting climate change. Individual source measurements provide the details necessary to develop actionable mitigation strategies and are highly complementary to mobile surveys and other top-down methods. Here, we perform 615 individual source measurements in Montréal, Canada, to quantify CH4 emissions from historic landfills, manholes, and fugitive emissions from natural gas (NG) distribution systems. We find that in 2020, historic landfills produced 901 (452 to 1541, 95% c.i.) tons of CH4, manholes emitted 786 (32 to 2602, 95% c.i.) tons of CH4, and NG distribution systems emitted 451 (176-843, 95% c.i.) tons of CH4, placing them all within the top four CH4 sources in Montréal. Methane emissions from both historic landfills and manholes are not accounted for in any greenhouse gas inventory. We find that geochemistry alone cannot positively identify source subcategories (e.g., type of manhole or NG infrastructure) in almost all cases, although C2/C1 ratios can distinguish NG distribution sources from biogenic sources (historic landfills and manholes). Using our individual source measurement data, we show that historic landfills have the greatest potential for CH4 reductions but the highest mitigation costs, unless we target the highest emitting landfills. In contrast, CH4 emissions from manholes can be reduced at low costs, but reduction methods are commercially unavailable. For NG distribution, methods such as increasing repair rates for high-emitting industrial meters can greatly reduce mitigation costs and emissions. Overall, our results highlight the role of individual source measurements in developing actionable CH4 mitigation strategies to meet municipal, regional, and national climate action plans.

Effect of supplemental malic acid on methane mitigation in paddy straw based complete diet for sustainable animal production in indigenous dairy cattle

A study was conducted to evaluate the effect of supplemental malic acid on mitigation of methane emission for dairy cattle by in vitro and in vivo methods. The in vitro finding was validated by in vivo feeding trial in indigenous dairy cattle. Ten dairy cattle with uniform milk production were selected and divided into two groups with five animals each and they were fed with and without supplementation of malic acid at 0.39% in 60% paddy straw and 40% concentrate mixture based complete diet. The malic acid at 0.39% was the minimum level which resulted in highly significant reduction of methane by 15.95% and methane (ml) per 100 mg of truly digested substrate by 15.69%, respectively than control in in vitro study. The methane emission per animal per day and per kg dry matter intake (DMI) was significantly decreased by 3.26% and 3.11%, respectively in malic acid supplemented group than control. The methane emission per kg milk production was significantly reduced by 5.43% in malic acid supplemented group than control. The total volatile fatty acid (TVFA) and propionic acid were significantly increased by 2.69% and 11.71%, respectively in malic acid supplemented group than control. It was concluded that the supplementation of malic acid at 0.39% of paddy straw based complete diet significantly reduced the methane emission per animal per day and per kg milk production than control in indigenous dairy cattle.

Combining fluoride with either phenolic compounds or plant extracts offers potential mitigation strategy for ammonia and methane emissions from livestock manure

Emissions of ammonia and methane from agriculture caused by microbes in manure are an increasing challenge to sustainable agriculture. We screened several commercially available polyphenols, phenolic compounds, and polyphenol-rich extracts for their ability to inhibit the production of ammonia and mitigate methane emissions in pig manure in the absence and presence of sodium fluoride (NaF) using a short-term high-throughput set-up. Tested compounds were chlorogenic acid, lignosulfonic acid, lignin, chitosan, green tea extract, and chestnut tannins. Green tea extract, at a concentration of 8.5 mg/ml with 1 mM NaF, reduced total ammonia nitrogen (TAN) in pig manure by 72%, while methane emissions were lowered by 95% at an extract concentration of 2.5 mg/ml. The ability of four extracts of plant waste (spent coffee grounds, noble fir needles, shea meal, and rapeseed press cakes) to mitigate ammonia production and methanogenesis in pig manure was also investigated. Adding 7.0 ± 0.7 mg/ml of extract from shea meal, noble fir, or rapeseed press cake, or 3.2 mg/ml of coffee ground extract reduced TAN production in manure by approximately 50%. Shea meal and noble fir had the largest effect on methane emissions, with reductions of approximately 60%. Gallocatechin- and epigallocatechin-rich extracts appeared to be especially potent for the inhibition of methane emissions, while ammonia production could be inhibited by a variety of tannins. Based on the current work, we conclude that extracts from certain plants have the potential for use in sustainable manure management to reduce ammonia and methane emissions. • Sustainable mitigation of ammonia and methane emissions by the STAF technology. • Green tea and shea meal extracts exhibit synergy with fluoride against ammonia. • Polyphenols can be an effective way to reduce greenhouse gasses from manure.

Opportunities and Hurdles to the Adoption and Enhanced Efficacy of Feed Additives towards Pronounced Mitigation of Enteric Methane Emissions from Ruminant Livestock

This paper analyzes the mitigation of enteric methane (CH4) emissions from ruminants with the use of feed additives inhibiting rumen methanogenesis to limit the global temperature increase to 1.5 °C. A mathematical simulation conducted herein predicted that pronounced inhibition of rumen methanogenesis with pure chemicals or bromoform-containing algae with an efficacy higher than that obtained in most studies can be important to limiting global temperature increase by 2050 to 1.5 °C but will likely need to be accompanied by improved production efficiency and other mitigation measures. Currently, the most important limitations to the adoption of antimethanogenic feed additives are increased feeding cost without a consistent return in production efficiency and achieving sustained delivery of inhibitors to grazing animals, especially in extensive systems. Economic incentives could be applied in some countries to favor adoption of inhibitors. Changes in rumen microbial and whole animal metabolism caused by inhibiting methanogenesis could potentially be used to make the methanogenesis inhibition intervention cost-effective, although research in this direction is unlikely to yield results in the short term. Future research directions to maximize the adoption and efficacy of inhibitors of methanogenesis are examined.

Effects of different treatments of manure on mitigating methane emissions during storage and preserving the methane potential for anaerobic digestion

Current agricultural practices in regards to storage of manure come with a significant GHG contribution, due, to a big extent, to CH4 emissions. For example, in Denmark, the agricultural sector is responsible for about 11.1 metric tons of CO2 equivalents; only about 0.2 metric tons come directly from CO2, while 6.0 tons come from CH4. The present study aims at evaluating and comparing two methods based on their effect on suppressing CH4 emissions during storage as well as on preserving and enhancing CH4 yield in a subsequent anaerobic digestion step: the commonly applied acidification with H2SO4 as acidifying agent and thermal treatment at the mild temperatures of 70 and 90 °C (pasteurization). Although both treatments effectively suppressed CH4 emissions during storage, they exhibited a significant difference in preserving and/or enhancing the CH4 potential of manure. Specifically, thermal treatment resulted in 16–35% enhancement of CH4 potential, while acidification resulted in decreasing the CH4 yield by 6–23% compared to non-treated manure. Further investigation showed that storage itself positively affected the CH4 potential of treated manure in a subsequent anaerobic digestion step; this was attributed to microbial activity other than biomethanation during storage. In overall and based on the results obtained regarding suppression of CH4 emissions during storage as well as CH4 potential enhancement, pasteurization at the temperatures tested is a promising alternative to the broadly applied acidification of manure.

Assessing Methane Emissions From the Natural Gas Industry: Reviewing the Case of China in a Comparative Framework

The aim of this paper is to explore methane emissions from China’s fossil fuel industry compared with the USA and Canada, with a focus on the methane emission mechanisms, calculation methods, mitigation potential, and abatement technologies. This paper explores the methane emissions from China’s natural gas industry from a comparative perspective. The main conclusions are as follows: (1) methane emissions from the natural gas production phase are the largest in the whole natural gas supply chain. (2) When it comes to measurement and estimation methods, methane emissions in the gas industry in the USA and Canada typically achieve a Tier 3 level, while China tends to be at the Tier 1 and Tier 2 levels. (3) There is large mitigation potential for methane emissions from the natural gas industry. More effective waste reduction technologies like green well completion should be implemented in the production phase, especially in China. At the same time, more attention should be drawn to the need for leakage detection technologies of pipelines in all countries compared here. As a large methane-emitting country, China lags behind the USA and Canada in methane emission reduction. Therefore, Chinese scientists, policy makers, and entrepreneurs should pay attention to methane emissions. Stakeholders should enhance mitigation measures and leakage detection technologies in order to achieve climate targets.

Strategies to Mitigate Enteric Methane Emissions in Ruminants: A Review

Methane is the main greenhouse gas (GHG) emitted by ruminants. Mitigation strategies are required to alleviate this negative environmental impact while maintaining productivity and ruminants’ health. To date, numerous methane mitigation strategies have been investigated, reported and suggested by scientists to the livestock industry. In this review, the authors will focus on the commonly practiced and available techniques expanding the knowledge of the reader on the advances of methane mitigation strategies with a focus on the recent literature. Furthermore, the authors will attempt to discuss the drawbacks of the strategies in terms of animal health and performance reduction as well as the concept of feed and energy loss, adding an economic perspective to methane emission mitigation which is in the farmers’ direct interest. As a whole, many factors are effective in reducing undesired methane production, but this is definitely a complex challenge. Conclusively, further research is required to offer effective and efficient methane production mitigation solutions in ruminants worldwide, thus positively contributing to climate change.

Development of a High-Accuracy Statistical Model to Identify the Key Parameter for Methane Adsorption in Metal-Organic Frameworks

The geometrical and topological features of metal-organic frameworks (MOFs) play an important role in determining their ability to capture and store methane (CH4). Methane is a greenhouse gas that has been shown to be more dangerous in terms of contributing to global warming than carbon dioxide (CO2), especially in the first 20 years of its release into the atmosphere. Its accelerated emission increases the rate of global temperature increase and needs to be addressed immediately. Adsorption processes have been shown to be effective and efficient in mitigating methane emissions from the atmosphere by providing an enormous surface area for methane storage. Among all the adsorbents, MOFs were shown to be the best adsorbents for methane adsorption due to their higher favorable steric interactions, the presence of binding sites such as open metal sites, and hydrophobic pockets. These features may not necessarily be present in carbonaceous materials and zeolites. Although many studies have suggested that the main reason for the increased storage efficiencies in terms of methane in the MOFs is the high surface area, there was some evidence in certain research works that methane storage performance, as measured by uptakes and deliveries in gravimetric and volumetric units, was higher for certain MOFs with a lower surface area. This prompted us to find out the most significant property of the MOF, whether it be material-based or pore-based, that has the maximum influence on methane uptake and delivery, using a comprehensive statistical approach that has not previously been employed in the methane storage literature. The approach in our study employed various chemometric techniques, including simple and multiple linear regression (SLR and MLR), combined with different types of multicollinearity diagnostics, partial correlations, standardized coefficients, and changes in regression coefficient estimates and their standard errors, applied to both the SLR and MLR models. The main advantages of this statistical approach are that it is quicker, provides a deeper insight into experimental data, and highlights a single, most important, parameter for MOF design and tuning that can predict and maximize the output storage and capture performance. The significance of our approach is that it was modeled purely based on experimental data, which will capture the real system, as opposed to the molecular simulations employed previously in the literature. Our model included data from ~80 MOFs and eight properties related to the material, pore, and thermodynamics (isosteric adsorption energy). Successful attempts to model the methane sorption process have previously been conducted using thermodynamic approaches and by developing adsorption performance indicators, but these are either too complex or time-consuming and their data covers fewer than 10 MOFs and a maximum of three MOF properties. By comparing the statistical metrics between the models, the most important and statistically significant property of the MOF was determined, which will be crucial when designing MOFs for use in storing and delivering methane.

Distribution pattern of N-damo bacteria along an anthropogenic nitrogen input gradient from the coastal mangrove wetland to the South China sea sediments

Microbial nitrite-dependent anaerobic methane oxidation (n-damo) process is important for mitigating methane emission and anthropogenic nitrogen inputs in the marine environment. However, the distribution pattern of n-damo bacteria along an anthropogenic N-input gradient from the coastal wetland to the pristine South China Sea is poorly understood. This study investigated the diversity and abundance of n-damo bacteria in samples collected along a N-input gradient from Mai Po (MP) mangrove wetland sediments of the Pearl River Estuary (PRE) to the deep ocean sediments of the South China Sea (SCS). Retrieved 16S rDNA sequences showed a shift of n-damo community composition of complex structures with both freshwater and marine n-damo lineages in MP intertidal sediments to marine dominated characteristic in SCS sediments. The observed variation of Shannon and Chao1 indexes of n-damo bacteria shared a similar trend of a decrease at first followed by an increase along the targeting gradient with previously investigated methanogens, anaerobic methanotrophic archaea, ammonia-oxidizing archaea and ammonia-oxidizing bacteria, but had a reverse pattern with anammox bacteria. The community structure of pmoA gene sequences contained freshwater lineages only in SCS continental shelf sediments closer to the PRE, and turned to group with other marine samples in deeper and pristine sediments. Results suggested that n-damo bacteria might be a major contributor to anaerobic denitrification in the SCS sediments because their abundances were much higher than previously studied anammox bacteria in the same sample set. The distribution pattern of n-damo bacterial diversity, richness and abundance along the anthropogenic N-input gradient implies that they could be used as a bio-indicator for monitoring the anthropogenic/terrestrial inputs in marine environments.

Effect of gradual increase of atmospheric CO2 concentration on nitrate-dependent anaerobic methane oxidation in paddy soils

Nitrate-dependent anaerobic oxidation of methane (AOM) is a new pathway to reduce methane emissions from paddy ecosystems. The elevated atmospheric CO2 concentration can affect methane emissions from paddy ecosystems, but its impact on the process of nitrate-dependent AOM is poorly known. Based on the automatic CO2 control platform with open top chambers and the 13CH4 stable isotope experiments, the responses of the activity of nitrate-dependent AOM, abundance and community composition of Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like archaea to the gradual increase of CO2 concentration were investigated in paddy fields. We set up two CO2 concentration treatments, including an ambient CO2 and a gradual increase of CO2(increase of 40 μL·L-1 per year above ambient CO2 concentration until 160 μL·L-1). The results showed the nitrate-dependent AOM rate of 0.7-11.3 nmol CO2·g-1·d-1 in the studied paddy fields, and quantitative PCR showed the abundance of M. nitroreducens-like archaeal mcrA genes of 2.2×106-8.5×106 copies·g-1. Compared to the ambient CO2 treatment, the slow elevated CO2 treatment enhanced the nitrate-dependent AOM rate and stimulated the abundance of M. nitroreducens-like archaea, particularly in 5-10 cm soil layer. The gradual increased CO2 concentration treatment did not change the community composition of M. nitroreducens-like archaea, but significantly decreased their diversity. The soil organic carbon content was an important factor influencing the nitrate-dependent AOM process. Overall, our results showed that the gradual increase of CO2 concentration could promote the nitrate-dependent AOM, suggesting its positive role in mitigating methane emissions from paddy ecosystems under future climate change.

Methane emissions and global warming: Mitigation technologies, policy ambitions, and global efforts

Methane emissions are the second highest contributor to climate change. Despite having a much lower atmospheric concentration than carbon dioxide, anthropogenic methane emissions account for almost one-third of anthropogenic warming since the pre-industrial period. Recently, the reduction of methane emissions has been recognized as an effective lever for reducing the impact of climate change in the next decade with less drastic economic and industrial costs than equivalent carbon dioxide mitigation. However, the wide range of methane emission sources, many of which are intermittent and at low concentration, poses a challenge for current detection and mitigation tools. Promising technical progress has been made on both fronts over the past decade, especially within the oil and gas sector, yet widespread implementation of mitigation policies and technologies lags considerably. The 2021 Global Methane Pledge for a 30% reduction in emissions by 2030 signals an increase in political will and can be achieved with these existing tools. It is estimated that the majority of these reductions can be accomplished through revenue-neutral or positive actions. Yet, a faster rate of reductions and sustained reductions beyond what is already available will be needed to maintain a 1.5◦C pathway. In the long term, more comprehensive policies, coupled with significant innovations in methane emission monitoring and mitigation, could enable an effective climate change mitigation strategy.

Enteric methane emission factors, total emissions and intensities from Germany's livestock in the late 19th century: A comparison with the today's emission rates and intensities

In its climate protection law, Germany pursues the aim of achieving greenhouse gas neutrality by 2045. To approach this aim, the emissions from all sectors shall be reduced by 65 % by 2030 relative to 1990 and this includes mitigation of enteric methane (CH4) emissions from livestock. The enteric CH4 emission rate must be reduced to 853 kt CH4 by 2030, but if this target rate reaches the level of the pre-agroindustrial era remains to be evaluated. The present study aimed to determine enteric CH4 emission factors, emission rates and intensities for Germany in the 19th century. Historical data about animal numbers in the German Empire were normalized to Germany's current territory. Body weight and performance data of livestock were available for 1883 and 1892. By using Tier 1 and Tier 2 approaches we found that oxen and bulls had the greatest emission factors, followed by dairy cows and young cattle. The annual enteric CH4 emissions from livestock amounted to 898 kt in 1883 and 1061 kt in 1892. Thus, the 2030-emission target is set 45 kt below the emission level of 1883, and livestock in Germany has been emitting comparable amounts or less enteric CH4 since 2003 relative to 1892. Animal performance increased, and while CH4 emission intensities for meat and milk production decreased from 1883 to 1892, these values were higher than values from 1991 to 2020. Although the human population of Germany's current territory more than doubled in the last 130 years, increased gain in animal performance allowed for the reduction in the numbers of ruminants at least during the last 35 years, resulting in declining CH4 emissions. Such a strategy may also be applied by other countries with steadily increasing human populations to balance CH4 emissions and food production from livestock.

Rumen eukaryotes are the main phenotypic risk factors for larger methane emissions in dairy cattle.

Mitigation of methane emissions from dairy cattle is a relevant strategy to reduce environmental impact from livestock as well as to increase farm profitability through improvement of energy usage. The objective of this study was to compare how microbiome composition determines methane concentration (MET) and methane intensity (MI, ppm CH4/kg Milk) with other traditional proxies (e.g. milk yield and conformation traits). A total of 1359 Holstein cows from 17 herds in 4 northern regions of Spain were included in this study. Microbiome data came from a subset of 437 cows from 14 herds. Cows were classified in quartiles for MET and MI, according to individual records of methane measurements during the cow's visit to the automatic milking system unit. A probit approach under a Markov chain Monte Carlo (McMC) Bayesian framework was used to determine risk factors for high MET and high MI. Reducing MET and MI genetic merit by unit of standard deviation (SD) reduced the probability of being classified in the upper quartile by 35.2% (33.9% to 36.4%) and 28.8% (27.6% to 29.6%), respectively. Increasing the relative abundance of most bacteria reduced the probability of a cow to be classified as high emitter (e.g., Firmicutes 9.9% (8.3 to 11.3) for MET and 7.1% (6.2 to 8.2) for MI, per unit of SD). An opposite effect was observed for the relative abundance of Eukaryotes. Larger abundance of most eukaryote caused larger risk for a cow to be classified as a high emitter animal (e.g., Oomycetes 14.2% (11.7% to 16.4%) for MET and 11.8% (9.4% to 14.0%) for MI, per unit of SD). One more unit of milk yield SD increased the probability of being classified in the upper quartile for MET by 3.7% (2.3% to 4.2%) and reduced the probability for MI by 12.6% (12.2% to 13.3%). Structure and capacity traits were not main drivers of being classified in the higher quartile of methane emission and intensity, with risk odds lower than 2% per unit of SD. Cow genetic merit for methane concentration and her microbiome composition (86 phylum and 1240 genus) were the main drivers for a cow to be classified as high MET or MI. This study suggests that mitigation of MET and MI could be addressed through animal breeding programs including genetic merits and strategies that modulate the microbiome.

Modulatory effects of dietary tannins on polyunsaturated fatty acid biohydrogenation in the rumen: A meta-analysis

BackgroundTannins are a group of phenolic compounds that can modify the rumen biohydrogenation (BH) of polyunsaturated fatty acids (PUFA), but to date results obtained have been inconsistent. This study therefore aims to conduct a meta-analysis of the scientific literature related to the effects of tannins on rumen BH and fermentation. MethodsA total of 28 articles were collected from various scientific databases, such as Scopus, Science Direct and Google Scholar, and the data were analysed using a random effects model and meta-regression for rumen BH. The publication bias on the main variables of rumen fermentation was assessed using a funnel plot and Egger's test. ResultsAn increase in tannin levels significantly reduced methane production (p < 0.001) and the population of Butyrivibrio fibrisolvens (p < 0.05). Dietary tannins also decreased the SFA proportion (p < 0.001) and increased (p < 0.001) the rumen monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) proportions. In additions, there were negative relationships between dietary tannin levels and BH rates of C18:2 n-6 and C18:3 n-3 (p < 0.05). ConclusionDietary tannins modulate the rumen fermentation profile, mitigate methane emissions, and inhibit rumen BH of PUFA.

Mitigation of methane emissions from three Danish landfills using different biocover systems

The establishment of biocover systems is an emerging methodology in reducing methane (CH4) emissions from landfills. This study investigated the performance of three biocover systems with different designs (biowindow and passively and actively loaded biofilters) in mitigating CH4 emissions from three landfills in Denmark. A series of field tests were carried out to evaluate the functionality of each system, and total CH4 emissions from relevant landfill sections or the entire landfill were measured before and after biocover implementation. Surface CH4 concentration screening and local CH4 fluxes showed generally low emissions from the biowindow/biofilters (mostly < 5 g CH4 m−2 d−1), although some hotspots were identified on two actively loaded biofilters. One passively loaded biofilter exhibited high CH4 emissions, mainly due to gas overloading into the system. Gas concentration profiles measured at different locations suggested uneven gas distribution in the biofilters, and significant CH4 oxidation occurred in both the gas distribution layer (when oxygen was fed into the system) and the CH4 oxidation layer. High CH4 oxidation efficiencies of above 95% were found in all systems except for one biofilter (55%). Whole-site emission measurements showed CH4 reduction efficiencies between 29 and 72% after implementing biocover systems at the three landfills, suggesting that they were efficient in reducing CH4 emissions. The most challenging task for the passively loaded biocover systems was to control gas flow and secure homogenous gas distribution, while for actively loaded biocovers, it might be more important to eliminate emission hotspots for better functionality.

First evidence for anaerobic oxidation of methane process in landfill cover soils: Activity and responsible microorganisms

Landfill cover soils (LCS) play important roles in mitigating methane emissions from landfills. Anaerobic oxidation of methane (AOM) has been demonstrated as a potential methane removal process in aquatic ecosystems. However, whether AOM could occur in LCS is largely unknown. Here, microcosm incubations with 13CH4 were applied to track the potential activities of AOM and quantitative PCR was used to identify the responsible microorganisms. AOM was found to be active in the bottom and middle layers of LCS. In the bottom layer, sulfate-AOM was the most active process, mainly dominated by ANME archaea (without ANME-2d). Meanwhile, in the middle layer, nitrate and nitrite were the major electron acceptors involved in AOM with high abundances of ANME-2d archaea and NC10 bacteria. Our results implied a spatial segregation of methane oxidizing microbes in LCS and might be helpful for future control of methane emissions by the enhancement of AOM.

Total Methane and CO2 Emissions from Liquefied Natural Gas Carrier Ships: The First Primary Measurements.

Mitigating methane emissions is vital in meeting global climate targets, but there is a lack of understanding of emissions and abatement opportunities to enable this. The natural gas supply chain is a key emission source, where methane emissions from liquefied natural gas (LNG) shipping have until now not been directly measured. This study provides the first measurement and modeling of total methane and CO2 emissions from an LNG carrier on a round trip voyage from the USA to Belgium and back, including loading, laden voyage, unloading, and ballast voyage, measuring emissions from exhaust stacks, vents, and fugitives. Venting and fugitive emissions were extremely low, contributing less than 0.1% of total greenhouse gas emissions. CO2 emissions from fuel usage were also lower than previous estimates due to improved efficiencies in modern engines and ship design. However, methane slip through the engines were higher than those in prior studies, averaging 3.8% across all engines: equating to 0.1% of delivered LNG. Generator engines are not typically included in emissions analyses but were the key cause of methane emissions. Engines exhibited higher methane slip rates at low loads, and optimized operation could reduce slip rates by half. More measurement studies are now needed to better understand fleet emissions and enable cost-effective mitigation strategies.

Constraining well integrity and propensity for fugitive gas migration in surficial soils at onshore decommissioned oil and gas well sites in England

Petroleum resource development generates a legacy of energy wells that must be decommissioned effectively as we transition towards NetZero. Unfortunately, some decommissioned wells (DWs) can suffer integrity failure resulting in release of fugitive natural gas into the surrounding soils and atmosphere. After decommissioning there are typically no ongoing assessments to confirm well integrity, meaning integrity status remains uncertain into the future. Furthermore, factors affecting fugitive natural gas migration in surficial soils around DWs are poorly recognized, inferring integrity assessment and monitoring strategies are lacking. To better understand the integrity status of DWs, identify soil properties controlling fugitive gas migration and help develop more effective monitoring and detection methodologies, we undertook field investigations at six DWs in England involving surficial CH4 measurements, sub-surface soil-gas and sediment sampling and dynamic flux-chamber measurements. We found no evidence of integrity failure at any site. However, the composition and structure of soils in which examined DWs are embedded suggest fugitive gas migration to surface may be severely limited; potentially mitigating methane emissions while making integrity assessment at the surface challenging. Overall, the integrity status of DWs in England is poorly constrained and we show surficial soil properties must be characterised and considered to effectively constrain the fate of fugitive gas and in order to design effective field assessment and monitoring methods.