Role Of Methane Research Articles

Methane Advances: Trends and Summary from Selected Studies

The role of methane (CH4) in the 21st century presents a critical dilemma. Its abundance and clean-burning nature make it a promising energy source, while its potent greenhouse effect threatens climate stability. Despite its potent greenhouse gas (GHG) nature, CH4 remains a crucial energy resource. However, advancements in CH4 capture, utilization, and emissions mitigation are rapidly evolving, necessitating a critical assessment of the advances, their potential, and challenges. This study aims to comprehensively evaluate the current state of the art in these advancements, particularly focusing on the emissions trends, with corresponding global warming potentials of projected CH4 emissions, and a discussion on the advances that have been made towards reducing the impacts of CH4 emissions. The areas of these advances include measurement, computational, numerical modeling, and simulation studies for CH4, emerging technologies for CH4 production, management and control, the nexus of CH4 –X, and case study applications in countries. This study reports on these advances, which involves a technical review of studies, mainly from the last decade, discussing the technical feasibility, economic viability, and environmental impact of these advancements. Our trend analysis reveals that even though the share of CH4 in the GHG mix has been around 19% compared with carbon dioxide (CO2), still, CH4 reduction would need to be highly subsidized because of the high global warming potential it has, compared with CO2. We conclude that while significant progress has been made, further research and development are essential to optimize the performance, scalability, and affordability of these advancements. Additionally, robust policy frameworks and international collaborations are crucial to ensure widespread adoption and maximize the potential that comes with the advancements in the mitigation of the impact of CH4 emission. This study contributes to the ongoing dialogue on balancing the potentials of CH4 with its environmental footprint, paving the way for a future where this versatile resource can be utilized sustainably.

Role of methane in ammonia combustion in air: From microscale to macroscale

Ammonia (NH3) has gained increasing recognition as a carbon-free fuel. To enhance NH3 combustion, reactive gases, like methane (CH4), are usually added to the combustion system. In this work, the role of CH4 in NH3 combustion is systematically studied. A series of reactive force field molecular dynamic (ReaxFF MD) simulations are implemented to investigate effects of CH4 addition on the consumption of NH3 and the yields of nitrogen oxides (NOx) from the atomic perspective: CH4 accelerates the consumption of NH3 by shortening the decomposition time of the first NH3 molecule and increasing the translational kinetic energy of the system; CH4 modifies the yield of NOx by complicating the elementary reactions and introducing additional intermediates. The fuel ratio of CH4 and NH3 between 0.5 and 1 is suggested for a cleaner and enhanced NH3 combustion. By summarising the findings from the latest publications and the present work, the role of CH4 in NH3 combustion is comprehensively analysed from the macroscale and microscale perspectives: CH4 accelerates the progress of NH3 combustion flame, activates chemical reactions, and aggravates NOx emissions at a low CH4 content. Taking the NH3/CH4 combustion as an example, this study provides an exclusive perspective to understand combustion phenomena from the microscale events to macroscale observations.

Molecular mechanism in the solubility reduction of elemental sulfur in H2S/CH4 mixtures: A molecular modeling study

The solubility evolution of elemental sulfur in sour gas is key to study the occurrence and inhibition of sulfur deposition in the exploitation of high-sulfur gas reservoirs. Elemental sulfur mainly dissolves in H2S, and its solubility decreases dramatically in the presence of methane. As both methane and H2S are the main components in high-sulfur gas, it is essential to understand the molecular mechanism of the solubility reduction in H2S/CH4 mixtures. Molecular dynamics simulations are carried out for the S8, H2S and CH4 mixtures to reproduce the solubility reduction upon methane addition, and then used to reveal the reduction mechanism at the level of intermolecular interaction. The simulations reveal that both the strong competitiveness and high collision probability of H2S–CH4 pairs reduce the average densities of H2S–S(S8) and H2S–H2S pairs, which reduce the sulfur solubility in a direct/indirect but cooperative way. The role of methane in the solubility reduction is then discussed and the molecular mechanism of sulfur dissolution and precipitation in the sour gasses is addressed.

Role of methane as a cushion gas for hydrogen storage in depleted gas reservoirs

Depleted natural gas reservoirs play an important role as a viable option for large-scale hydrogen storage and production. However, its deployment depends on the accurate knowledge of the cushion gas (such as CH4, CO2, and N2) compositions, which are key components affecting the rock-fluid interfacial phenomenon. In addition, there are currently few reported studies on rock/brine/gas-mixture wettability and gas-mixture/brine surface tension representing this type of reservoir. Hence, we report the feasibility of using CH4 as a cushion gas (in the presence of CO2 and N2) for H2 storage at various pressures (500 up to 3000 psi), temperatures (30 up to 70) oC, and salinities (2 up to 20) wt.% using drop shape analyzer equipment. Contact angle (CA) and surface tension (ST) experiments were extensively conducted for the different gas mixtures (H2–CH4–CO2–N2) to establish relevant data for H2 storage in depleted gas reservoirs.Our result indicates that unless when the rock's initial wetting state is altered, the studied gas-mixture compositions (Test case 1: 80% H2 – 10% CH4 – 5% CO2 – 5% N2; case 2: 70% H2 – 20% CH4 – 5% CO2 – 5% N2; case 3: 60% H2 – 30% CH4 – 5% CO2 – 5% N2; case 4: 50% H2 – 40% CH4 – 5% CO2 – 5% N2; case 5: 40% H2 – 50% CH4 – 5% CO2 – 5% N2; case 6: 30% H2 – 60% CH4 – 5% CO2 – 5% N2; and case 7: 20% H2 – 70% CH4 – 5% CO2 – 5% N2) will exhibit comparable wettability behavior as the CAs ranged between [20 to 41°] irrespective of the reservoir pressure, temperature, and salinity. ST decreases with increasing temperature and linearly with increasing pressure. ST for each gas mixture increased with salinity. ST decreases systematically with increasing CH4 fraction (at any given salinity, temperature, and pressure) with the highest observed in Test case 1 and the lowest in Test case 7 compositions. Test cases 3 and 4 with H2 (50–60%) and CH4 (30–40%) fractions was selected as the optimal gas mixture based on CA and ST for H2 storage and withdrawal. The study's findings offer precise and useful input data for the reservoir-scale simulation used in geo-storage optimization in depleted natural gas reservoirs.

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.

Efficient nitrogen removal from mainstream wastewater through coupling Partial Nitritation, Anammox and Methane-dependent nitrite/nitrate reduction (PNAM)

The application of partial nitritation and anammox to remove nitrogen from mainstream wastewater is of great interest because of the potential to reduce energy cost and carbon dosage. However, this process confronts a dilemma of relatively high effluent nitrogen concentration (>10 mg N/L), owning to the unwanted prevalence of nitrite-oxidizing bacteria (NOB) and the intrinsic nitrate production by anammox bacteria. Here, a novel technology, named the one-stage PNAM, that integrates Partial Nitritation, Anammox and Methane-dependent nitrite/nitrate reduction reactions, was developed in a single membrane biofilm reactor (MBfR). With feeding of synthetic mainstream wastewater containing ∼50 mg NH4+-N/L at a hydraulic retention time of 12 h, more than 95% nitrogen was removed in the established one-stage PNAM process at a practically useful rate of 0.1 kg N/m3/d. Microbial community characterization and in-situ batch tests revealed a sophisticated microbial structure consisting of ammonia-oxidizing bacteria (AOB), anammox bacteria, nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) bacteria and archaea, and a small fraction of NOB and aerobic methanotrophs. The role of methane in removing nitrate was confirmed by switching on/off the methane supply, which relaxed the requirement for NOB suppression. In addition, the established system was relatively robust against temperature variations, evidenced by a total nitrogen removal efficiency above 80% at temperature as low as 14 ℃. The results provide a promising alternative for efficient nitrogen removal from domestic wastewater using methane as the sole carbon source.

Volumetric Mapping of Methane Concentrations at the Bush Hill Hydrocarbon Seep, Gulf of Mexico

The role of methane as a green-house gas is widely recognized and has sparked considerable efforts to quantify the contribution from natural methane sources including submarine seeps. A variety of techniques and approaches have been directed at quantifying methane fluxes from seeps from just below the sediment water interface all the way to the ocean atmosphere interface. However, there have been no systematic efforts to characterize the amount and distribution of dissolved methane around seeps. This is critical to understanding the fate of methane released from seeps and its role in the submarine environment. Here we summarize the findings of two field studies of the Bush Hill mud volcano (540 m water depth) located in the Gulf of Mexico. The studies were carried out using buoyancy driven gliders equipped with methane sensors for near real time in situ detection. One glider was equipped with an Acoustic Doppler Current Profiler (ADCP) for simultaneous measurement of currents and methane concentrations. Elevated methane concentrations in the water column were measured as far away as 2 km from the seep source and to a height of about 100 m above the seep. Maximum observed concentrations were ∼400 nM near the seep source and decreased away steadily in all directions from the source. Weak and variable currents result in nearly radially symmetric dispersal of methane from the source. The persistent presence of significant methane concentrations in the water column points to a persistent methane seepage at the seafloor, that has implications for helping stabilize exposed methane hydrates. Elevated methane concentrations in the water column, at considerable distances away from seeps potentially support a much larger methane-promoted biological system than is widely appreciated.

Heterologous expression and assembly of methyl‐coenzyme M reductase from anaerobic methanotrophs

Methyl-coenzyme M reductase (MCR) is the key rate-determining enzyme of methanogenesis and anaerobic oxidation of methane, the essential energy metabolisms of methanogenic archaea and anaerobic methanotrophs (ANME), respectively. Given the role of methane as both a potent greenhouse gas as well as a valuable energy source, understanding the biochemistry of its production and consumption in nature is becoming increasingly important. Extensive studies on methanogenic MCR have revealed key biochemical and mechanistic insights, however, the catalytic properties of ANME MCR have yet to be reported. This is due to the difficulties associated with culturing ANME organisms in a lab setting, which is hindered by extremely slow growth rates and a characteristic dependence of bacterial partners. MCR is a dimer of heterotrimers with a 2α, 2β, 2γ configuration and requires the unique nickel tetrapyrrole prosthetic group, coenzyme F430, thus rendering MCR a difficult enzyme to be produced using a heterologous expression system. Here we report our progress in the development of such a system for expressing recombinant ANME MCRs in the model methanogen, Methanococcus maripaludis. This work lays the foundation for future biochemical and mechanistic studies of anaerobic C-H bond activation catalyzed by ANME MCR.

Microbial Communities in Methane Cycle: Modern Molecular Methods Gain Insights into Their Global Ecology

The role of methane as a greenhouse gas in the concept of global climate changes is well known. Methanogens and methanotrophs are two microbial groups which contribute to the biogeochemical methane cycle in soil, so that the total emission of CH4 is the balance between its production and oxidation by microbial communities. Traditional identification techniques, such as selective enrichment and pure-culture isolation, have been used for a long time to study diversity of methanogens and methanotrophs. However, these techniques are characterized by significant limitations, since only a relatively small fraction of the microbial community could be cultured. Modern molecular methods for quantitative analysis of the microbial community such as real-time PCR (Polymerase chain reaction), DNA fingerprints and methods based on high-throughput sequencing together with different “omics” techniques overcome the limitations imposed by culture-dependent approaches and provide new insights into the diversity and ecology of microbial communities in the methane cycle. Here, we review available knowledge concerning the abundances, composition, and activity of methanogenic and methanotrophic communities in a wide range of natural and anthropogenic environments. We suggest that incorporation of microbial data could fill the existing microbiological gaps in methane flux modeling, and significantly increase the predictive power of models for different environments.

Methane chemistry in a nutshell – the new submodels CH4 (v1.0) and TRSYNC (v1.0) in MESSy (v2.54.0)

Abstract. Climate projections including chemical feedbacks rely on state-of-the-art chemistry–climate models (CCMs). Of particular importance is the role of methane (CH4) for the budget of stratospheric water vapour (SWV), which has an important climate impact. However, simulations with CCMs are, due to the large number of involved chemical species, computationally demanding, which limits the simulation of sensitivity studies. To allow for sensitivity studies and ensemble simulations with a reduced demand for computational resources, we introduce a simplified approach to simulate the core of methane chemistry in form of the new Modular Earth Submodel System (MESSy) submodel CH4. It involves an atmospheric chemistry mechanism reduced to the sink reactions of CH4 with predefined fields of the hydroxyl radical (OH), excited oxygen (O(1D)), and chlorine (Cl), as well as photolysis and the reaction products limited to water vapour (H2O). This chemical production of H2O is optionally fed back onto the specific humidity (q) of the connected general circulation model (GCM), to account for the impact onto SWV and its effect on radiation and stratospheric dynamics. The submodel CH4 is further capable of simulating the four most prevalent CH4 isotopologues for carbon and hydrogen (CH4 and CH3D, as well as 12CH4 and 13CH4). Furthermore, the production of deuterated water vapour (HDO) is, similar to the production of H2O in the CH4 oxidation, optionally passed back to the isotopological hydrological cycle simulated by the submodel H2OISO, using the newly developed auxiliary submodel TRSYNC. Moreover, the simulation of a user-defined number of diagnostic CH4 age and emission classes is possible, the output of which can be used for offline inverse optimization techniques. The presented approach combines the most important chemical hydrological feedback including the isotopic signatures with the advantages concerning the computational simplicity of a GCM, in comparison to a full-featured CCM.

Role of Methane as a Second Guest Component in Thermodynamic Stability and Isomer Selectivity of Butane Clathrate Hydrates

The role of guest–guest and guest–host interactions has been studied in the case of butane-based hydrates. It has been shown that these interactions are different for n-butane and iso-butane isomer...

The role of methane in the formation of fullerene-like nanostructure in amorphous carbon film deposited by reactive magnetron sputtering

The formation of fullerene-like nanostructure in amorphous carbon film is an efficient way to improve the toughness without reducing the hardness of hydrogenated amorphous carbon film. In this paper, a convenient approach to regulating the growth of fullerene-like nanostructure by reactive magnetron sputtering process utilizing graphite target in mixed methane and argon plasma was reported and the role of methane in the formation of fullerene-like nanostructure in amorphous carbon film was discussed. By adjusting the degree of graphite target poisoning, fullerene-like nanostructure was successfully produced in the carbon film. In order to reveal the growth mechanism of this special structure, the structural evolution of the film and graphite target surface were studied. The results suggest that the structure of the target surface and the film are both amorphous carbon when target poisoning severely, and the fullerene-like nanostructure appears in carbon film when target poisoning slightly. However, when methane was not admitted into the chamber, the target was not poisoned, non‑hydrogenated carbon film was prepared. The structure of non‑hydrogenated carbon film is graphite-like. Therefore, that shows the important effect of target poisoning on the structure of film and methane plays an important role in the formation of fullerene-like nanostructure in amorphous carbon film. The formation of the fullerene-like nanostructure is attributed to the deposition of ionized methane on the target surface, which is introduced sp3-hybridized carbon atoms into the graphite structure, resulting in the curvature of the graphite 2D-plane. Nonetheless, when a large amount of methane plasma deposits on the target surface will cause target poisoning severely, the structure of the target surface and the film are both amorphous carbon.

Methylotrophic methanogens everywhere - physiology and ecology of novel players in global methane cycling.

Research on methanogenic Archaea has experienced a revival, with many novel lineages of methanogens recently being found through cultivation and suggested via metagenomics approaches, respectively. Most of these lineages comprise Archaea (potentially) capable of methanogenesis from methylated compounds, a pathway that had previously received comparably little attention. In this review, we provide an overview of these new lineages with a focus on the Methanomassiliicoccales. These lack the Wood-Ljungdahl pathway and employ a hydrogen-dependent methylotrophic methanogenesis pathway fundamentally different from traditional methylotrophic methanogens. Several archaeal candidate lineages identified through metagenomics, such as the Ca. Verstraetearchaeota and Ca. Methanofastidiosa, encode genes for a methylotrophic methanogenesis pathway similar to the Methanomassiliicoccales. Thus, the latter are emerging as a model system for physiological, biochemical and ecological studies of hydrogen-dependent methylotrophic methanogens. Methanomassiliicoccales occur in a large variety of anoxic habitats including wetlands and animal intestinal tracts, i.e. in the major natural and anthropogenic sources of methane emissions, respectively. Especially in ruminant animals, they likely are among the major methane producers. Taken together, (hydrogen-dependent) methylotrophic methanogens are much more diverse and widespread than previously thought. Considering the role of methane as potent greenhouse gas, resolving the methanogenic nature of a broad range of putative novel methylotrophic methanogens and assessing their role in methane emitting environments are pressing issues for future research on methanogens.

The role of methane in plant physiology: a review.

Methane (CH4), one of the most important greenhouse gases, has conventionally been considered as a physiologic inert gas. However, this perspective has been challenged by the observation that CH4 has diverse biological functions in animals, such as anti-inflammatory, antioxidant, and anti-apoptosis. Meanwhile, it has now been identified as a possible candidate of gaseous signaling molecule in plants, although its biosynthetic and metabolic pathways as well as the mechanism(s) of CH4 signaling have not fully understood yet. This paper aims to review the available evidence for the biological roles of CH4 in regulating plant physiology. Although currently available reports do not fully support the notion of CH4 as a gasotransmitter, they do show that CH4 might be produced by an aerobic, non-microbial pathway from plants, and plays important roles in enhancing plant tolerance against abiotic stresses, such as salinity, drought, heavy metal exposure, and promoting root development, as well as delaying senescence and browning. Further results showed that CH4 could interact with reactive oxygen species (ROS), other gaseous signaling molecules [e.g., nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S)], and glutathione (GSH). These reports thus support the idea that plant-produced CH4 might be a component of a survival strategy of plants. Finally, the possibility of CH4 application in agriculture is preliminarily discussed.

The role of methane in future climate strategies: mitigation potentials and climate impacts

This study examines model-specific assumptions and projections of methane (CH4) emissions in deep mitigation scenarios generated by integrated assessment models (IAMs). For this, scenarios of nine models are compared in terms of sectoral and regional CH4 emission reduction strategies, as well as resulting climate impacts. The models’ projected reduction potentials are compared to sector and technology-specific reduction potentials found in literature. Significant cost-effective and non-climate policy related reductions are projected in the reference case (10–36% compared to a “frozen emission factor” scenario in 2100). Still, compared to 2010, CH4 emissions are expected to rise steadily by 9–72% (up to 412 to 654 Mt CH4/year). Ambitious CO2 reduction measures could by themselves lead to a reduction of CH4 emissions due to a reduction of fossil fuels (22–48% compared to the reference case in 2100). However, direct CH4 mitigation is crucial and more effective in bringing down CH4 (50–74% compared to the reference case). Given the limited reduction potential, agriculture CH4 emissions are projected to constitute an increasingly larger share of total anthropogenic CH4 emissions in mitigation scenarios. Enteric fermentation in ruminants is in that respect by far the largest mitigation bottleneck later in the century with a projected 40–78% of total remaining CH4 emissions in 2100 in a strong (2 °C) climate policy case.

Hydrogen peroxide is involved in methane-induced tomato lateral root formation.

Pharmacological and molecular evidence reveals a novel role of methane (CH4) gas in root organogenesis, the induction of lateral root (LR) formation, and this response might require hydrogen peroxide (H2O2) synthesis. Although plants can produce CH4 and release this to atmosphere, the beneficial role(s) of CH4 are not fully elucidated. In this study, the fumigation with CH4 not only increased NADPH oxidase activity and H2O2 production, but also induced tomato lateral root primordial formation and thereafter LR development. However, exogenously applied argon and nitrogen failed to influence LR formation. Above responses triggered by CH4 were sensitive to the removal of endogenous H2O2 with dimethylthiourea (DMTU; a membrane-permeable scavenger of H2O2), suggesting the hypothesis that CH4's effect on LR formation could be mediated by endogenous H2O2. Diphenylene iodonium (DPI) inhibition of the H2O2 generating enzyme NADPH oxidase attenuated H2O2 synthesis and impaired LR formation in response to CH4, confirming the requirement of NADPH oxidase-dependent H2O2. Meanwhile, the alterations of endogenous H2O2 concentrations failed to influence CH4 production in tomato seedlings. Molecular evidence revealed that CH4-induced SlCDKA1, SlCYCA2;1, and SlCYCA3;1 transcripts, and -decreased SlKRP2 mRNA were impaired by DMTU or DPI. Contrasting changes in LR formation-related miR390a and miR160 transcripts and their target genes, including SlARF4 and SlARF16, were observed. Together, our pharmacological and molecular evidence suggested the requirement of H2O2 synthesis in CH4-triggered tomato LR formation, partially via the regulation of cell cycle regulatory genes, miRNA-, and tasiRNA-modulated gene expression.

The Role of Methane and Methane Hydrates in the Evolution of Global Climate

For the first time, functioning of the planetary climate system is considered in terms of the self-organization laws with account of positive and negative feedbacks. It is shown that the maximum risks in the development of positive feedbacks that can lead the climate system to a planetary catastrophe, are associated with an unprecedented increase in the concentration of methane in the atmosphere. Over the last 30 years, its concentration in the atmosphere has increased by 2.5 times and continues to grow exponentially. In this review, we show that today the principal source for increase of methane concentration in the atmosphere is the self-accelerating decomposition of methane hydrates in the cryosphere of the Northern Hemisphere. In the history of the Earth, the emissions of methane into the atmosphere due to mass decomposition of methane hydrates led to climate-induced biosphere catastrophes. Paleo-reconstruction analysis of greenhouse gas concentrations in the atmosphere and its temperature over the last 420,000 years has allowed us to conclude that the self-organizing planetary climate system is currently in a state of dynamic chaos (close to the bifurcation point). This means that even a relatively weak impact on it, also of anthropogenic characters, is able to affect the planetary climate system to select its future development trajectory.

Patterns of spatial methane distribution in the upper layers of permafrost in Central Yakutia

The article presents the results of long-term field studies of methane in the upper part of permafrost for the different geomorphological levels of Central Yakutia. Patterns of spatial distribution of methane content across different landscapes were found. The highest concentrations of methane are found in alas deposits, the major role of methane in the conservation there goes to the moment of freezing the thermokarst lake draining. The difference in methane content in the sediments of the Late Pleistocene Ice Complex on the left and the right bank of the river Lena was identified. That is likely caused by the conditions of ice complex formation.

Authigenic Mg-calcite at a cold methane seep site in the Laptev Sea

Authigenic minerals were studied in Holocene shelf sediments of the Laptev Sea (cold methane seep site, water depth 71 m). The study presents the first finds of large hard carbonate concretions with Mg-calcite cement in recent sediments of the Arctic shelf seas. These concretions differ from previously reported glendonites and concretions from bottom sediments of the White Sea, Kara Sea, Sea of Okhotsk, etc. A study of the morphology, microstructure, and composition of these newly reported concretions revealed the multistage formation of carbonates (structural varieties of Mg-calcite and aragonite). It was shown that organic matter played an important role in the formation of authigenic carbonates, i.e., in the formation of sedimentary–diagenetic Mg-calcite. The role of methane as a possible source for authigenic carbonate formation was estimated. It was found that methane-derived Mg-calcite accounts for 17–35% of concretion materials. Mg-calcite had δ13С-Сcarb values between–24 and–23‰ and δ13С-Сorg values between–44.5 and–88.5‰.

The Bacteriohopanepolyol Inventory of Novel Aerobic Methane Oxidising Bacteria Reveals New Biomarker Signatures of Aerobic Methanotrophy in Marine Systems.

Aerobic methane oxidation (AMO) is one of the primary biologic pathways regulating the amount of methane (CH4) released into the environment. AMO acts as a sink of CH4, converting it into carbon dioxide before it reaches the atmosphere. It is of interest for (paleo)climate and carbon cycling studies to identify lipid biomarkers that can be used to trace AMO events, especially at times when the role of methane in the carbon cycle was more pronounced than today. AMO bacteria are known to synthesise bacteriohopanepolyol (BHP) lipids. Preliminary evidence pointed towards 35-aminobacteriohopane-30,31,32,33,34-pentol (aminopentol) being a characteristic biomarker for Type I methanotrophs. Here, the BHP compositions were examined for species of the recently described novel Type I methanotroph bacterial genera Methylomarinum and Methylomarinovum, as well as for a novel species of a Type I Methylomicrobium. Aminopentol was the most abundant BHP only in Methylomarinovum caldicuralii, while Methylomicrobium did not produce aminopentol at all. In addition to the expected regular aminotriol and aminotetrol BHPs, novel structures tentatively identified as methylcarbamate lipids related to C-35 amino-BHPs (MC-BHPs) were found to be synthesised in significant amounts by some AMO cultures. Subsequently, sediments and authigenic carbonates from methane-influenced marine environments were analysed. Most samples also did not contain significant amounts of aminopentol, indicating that aminopentol is not a useful biomarker for marine aerobic methanotophic bacteria. However, the BHP composition of the marine samples do point toward the novel MC-BHPs components being potential new biomarkers for AMO.