Extinction .in

Methane accounts for more than one-quarter of the anthropogenic radiative imbalance since the pre-industrial age. Its largest sources include both natural and human-mediated pathways: wetlands, fossil fuels (oil/gas and coal), agriculture (livestock and rice cultivation), landfills, and fires. The dominant loss of methane is through oxidation in the atmosphere via the hydroxyl radical (OH). Apart from its radiative effects, methane impacts background tropospheric ozone levels, the oxidative capacity of the atmosphere, and stratospheric water vapor. As such, changes in the abundance of atmospheric methane can have profound impacts on the future state of our climate.

Since Methane has such an increased effect on climate change, especially in the short-term to medium-term (20 to 50 years), it must be addressed in every possible manner. Atmospheric methane plays a major role in controlling climate, yet contemporary methane trends (1982–2017) have defied explanation with numerous, often conflicting, hypotheses proposed in the literature. Specifically, atmospheric observations of methane from 1982 to 2017 have exhibited periods of both increasing concentrations (from 1982 to 2000 and from 2007 to 2017) and stabilization (from 2000 to 2007). Explanations for the increases and stabilization have invoked changes in tropical wetlands, livestock, fossil fuels, biomass burning, and the methane sink. Contradictions in these hypotheses arise because our current observational network cannot unambiguously link recent methane variations to specific sources. Thus, consensus cannot be reached on sources of methane. It is clear that better monitoring of methane sources and rates is needed. Some new technologies and systems in development can help address this lack of consensus and knowledge. It is my firm belief that putting funds towards discounting the 7 or so years of “stabilization” in the rise in methane concentrations in the atmosphere, since it must be an anomaly, in my and many other scientist's opinion, would help achieve consensus on this issue, and would really help get everyone, all stakeholders, on board our plans to stop producing methane as much as possible, and to mitigate and remove existing methane, which is critically needed.

Explanations of recent atmospheric methane trends can be broadly grouped based on the types of proxy measurements used. Measurements of δ13C-CH4 (the 13C/12Cratio in atmospheric methane) provide information about the fraction of methane coming from biotic (i.e., microbial) and abiotic sources, as biotic methane is produced enzymatically and tends to be depleted in 13C, making it isotopically lighter. Atmospheric ethane (C2H6 ) can be co-emitted with methane from oil/gas activity and, as such, has been used as a tracer for fossil methane emissions. Similarly, carbon monoxide can be co-emitted with methane from biomass burning. Methyl chloroform (CH3CCl3) is a banned industrial solvent that has been used to infer the abundance of the dominant methane sink (the hydroxyl radical, OH). These four measurements (δ13C-CH4, C2H6 , CO, and CH3CCl3) have been used in conjunction with atmospheric methane measurements. However, studies generally reached differing conclusions regarding the recent methane trends.

Studies using ethane have argued that decreases in fossil fuel sources led to the stabilization of atmospheric methane in the 2000s and that increases in fossil fuel sources contributed to the growth since 2007. Studies using isotope measurements tend to find that decreases in microbial sources led to the stabilization and increases in microbial sources are responsible for the renewed growth. Studies that include methyl chloroform measurements tend to find that changes in the methane sink played a role in both the stabilization and renewed growth. When measurements of carbon monoxide are included which inferred a decrease in biomass burning emissions, an isotopically heavy methane source, that helps reconcile a potential increase in both fossil fuel and microbial emissions. Natural sources and sinks (e.g., wetlands, fires, and OH) exhibit substantial variability on sub-decadal scales but we do not have a process/inventory-based explanation for a long-term trend. The long-term growth trend in atmospheric methane is best explained by the continued rise in anthropogenic emissions—even though the most uncertain sectors are predominantly natural (wetlands and OH)—and as long as anthropogenic emissions continue to rise we can expect a concurrent rise in atmospheric methane with variability superimposed due to fluctuations in natural sources and sinks.

New methods of monitoring methane sources and emissions. Satellite observations have proved to be be useful in constraining methane sources at local-to-regional scales but have thus far played a relatively limited role in the discussion of global methane trends because the record is short compared with in situ measurements. the first total column measurements of methane were made by Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) in 2003 and Greenhouse Gases Observing Satellite (GOSAT) is the longest-running satellite that measures total column methane with 9 y of data (measurements started in April 2009). Networks like the Total Carbon Column Observing Network (TCCON) and AirCore are crucial to identify biases in satellite measurements, evaluate their uncertainties, and facilitate inter-comparisons between different satellite instruments. Satellite observations will likely play a growing role in the discussion of future methane trends as the record length increases and new missions like the recently launched Tropospheric Monitoring Instrument (TROPOMI) and recently funded Geostationary Carbon Cycle Observatory (GeoCARB) instrument (geostationary orbit) emerge.

Current scientific thinking believes that while it is important to understand the potential for permafrost methane emissions, current uncertainties in the tropics greatly exceed the absolute magnitude of Arctic sources. I believe that both Arctic and Antarctic sources need to be included in any calculations, and that underwater AND undersea permafrost also needs to be calculated. Most calculations which include underwater permafrost only include freshwater, from which methane hydrates emerge. Furthermore I believe that it is because scientists are not taking into account the self-reinforcing natural systems feedback mechanisms which will cause a temperature increase of over 2-3 degrees atmospherically, at first, which will result in a further permafrost and ice melt, which will release more of the warming gases, including methane, currently locked in ice and permafrost, which will cause further temperature increases, and so on... This area of uncertainty needs to be addressed. This concern arises from suggestions that rapid methane release 55 million years ago at the boundary of the Paleocene and Eocene epochs triggered temperature increases of 5–8°C globally. A recent study in the nearshore environment of the ESAS showed that ice-bonded permafrost had retreated 14 cm yr−1 over the past three decades. Such subsea permafrost degradation or loss of coastal methane clathrates could lead to bursts of methane reaching the atmosphere, depending on water depth and other factors.

Even with present uncertainties on global methane trends, there have been a a number of recent advances in measurement technology that have tremendous potential for opportunistic mitigation (i.e., reducing emissions at no net cost). A few notable examples include identifying large fugitive leaks in oil and gas infrastructure and changing the diet of livestock. Specifically, remote sensing has demonstrated the ability to identify anomalous, large emitters and focused programs to use aircraft- or space-based observations to identify and mitigate emissions could prove cost efficient and effective. Recent advances in frequency-comb spectrometers and affordable, small ground-based sensors may also provide a mitigation opportunity for super-emitters in oil/gas basins. Changes in the diet of livestock could reduce the production of methane in dairy cattle without reducing milk production and, as such, could be an opportunity to reduce methane emissions from livestock. Implementation of these or other mitigation strategies could help to curb future increases in atmospheric methane and provide detectable changes in the global methane burden within decades.

So, first of all, every effort must be made to reduce production of methane in the first place.

Food additives to ruminant husbandry feed to reduce enterically produced methane is a great idea which must be advocated, subsidized where necessary and put into practice globally. Additionally, encouraging people to eat much less animal products, and introducing insect protein into the human diet where it doesn't already exist, and into animal feed, is also helpful and should be advocated. As a SOCIAL measure to change people's minds about warming gases, the natural aversion of so many people to becoming a vegetarian and to eating insects can be used to create a sense of urgency and critical importance to solving the climate crisis, so that they can remain meat-eaters without having to eat insects, once a solution is found.

Methane production in industrial processes should be reduced and where possible eliminated.

Second, methane removal from the atmosphere should be advocated, although there lacks a scientific consensus on whether or not this is feasible and if it is to be done, how it should be done. In my opinion it is clear that this must be done, because I believe it is too late to stop the permafrost melt which will double (or worse) methane concentrations in the atmosphere so that a tipping-point is passed at which point all ice on Earth will melt.

Methane removal poses the challenge of extreme dilution. The dilute concentration of methane in the atmosphere challenges economical removal. On a mass basis, methane is currently 600 times more dilute in Earth’s atmosphere than carbon dioxide. It is estimated that atmospheric methane removal would be one thousand time as expensive as CO2 removal, because it would require 1000 times the energy using current technology for removal of CO2 from the atmosphere. For methane, this eliminates fans and blowers as a practical means of moving air through sorbent beds; the amount of air that would need to be moved would simply be too great. However, it does not prohibit passive methods of removing methane. If methane is to be stripped out of the atmosphere, taking advantage of natural air flow provides a viable solution. Thus, more research should be done and action taken and projects started on methane removal with passive air flow methods and sorbants, and action must begin to be taken using the best methods, with the best sorbants, while passive air-flow still exists, since climate warming will probably put a stop to the atmospheric currents which currently exist, and upon which feasible passive air-flow methane removal depend.

Natural processes destroy roughly 10% of the methane in the atmosphere every year. To substantially enhance natural processes, methane removal units would have to process the entire atmosphere in less than a decade. Unlike carbon dioxide, which accumulates in the atmosphere and lingers for millennia—and for which nobody suggests such an ambitious scale—methane just flows rapidly in and out of the atmospheric reservoir. Thus it appears easier to curtail some natural emissions than to remove methane directly from the atmosphere. Once methane emissions are curbed, concentrations will decline rapidly. This stands in stark contrast to carbon dioxide emissions, which, by lingering, pose a stock (rather than a flow) problem. On the other hand, if climate feedbacks were to cause large methane releases from permafrost, as I believe will occur, passive collectors at a massive scale may still be the best option available. There is no real scientific consensus on this point, and consensus needs to be reached quickly because passive collection of methane on a massive scale will require considerable time and resources.

However, methane is not the only greenhouse gas with extremely low concentrations. Now that passive designs are opening the door to remediation of extremely low concentrations, another worthy target for catalytic removal may be long-lived nitrous oxide. Nitrous oxide is another greenhouse gas whose emissions are difficult to avoid; but in comparison to methane, its long lifetime greatly reduces the rate at which the atmosphere needs to be processed.

There are two other types of methane capture projects. The first type captures and burns (flares) methane. Through combustion, methane gas is turned into less potent carbon dioxide and water. Examples of such projects include the capture and flaring of landfill gas and of coal mining gas. The second type of project captures methane and uses it to produce either hot water, electricity, or pipeline-quality natural gas that is direct injected into the common carrier pipeline. Such projects include those that capture and purify methane in wastewater treatment plants, livestock anaerobic digesters, or landfills and use it for electricity production or the production of another form of energy.

Biofuel plants that use agricultural or forestry waste to produce electricity also use methane: organic matter is anaerobically digested, and the resulting methane is used to produce electricity. Such biofuel projects are often considered renewable energy projects rather than methane capture.

It is usually quite easy to establish cost efficiency for the first type of methane projects because there is generally no other source of revenue from the activity aside from the sale of offset credits. Yet, methane offset projects could potentially create disincentives to regulate landfills and agricultural emissions (e.g., from manure lagoons). If methane capture and destruction projects become profitable through the sale of offset credits, there is little incentive for project owners to support legislation that would mandate capture and destruction. This issue of perverse incentives could stifle more effective regulation is not limited to methane project but holds true for many offset types and potential regulation.

Not all offset project types are equally effective at producing the emissions reductions that they initially set out to deliver. Methane projects are notorious for underperforming. CDM landfill methane projects, for example, realize just 35% of their projected emissions reductions. Whether or not carbon offset projects are good policy is a matter on which there is a lack of both scientific and governmental or social public policy consensus, and this is an area which could be addressed, with an appropriate corresponding advocate for policy-makers. As policymakers consider options to reduce GHG emissions, methane capture projects offer an array of possible reduction opportunities, many of which utilize proven technologies.

Methane capture projects (e.g., landfill gas projects, anaerobic digestion systems) restrict the release of methane into the atmosphere. The methane captured can be used for energy or flared. Methane capture challenges differ depending on the source. Most methane capture technologies face obstacles to implementation, including marginal economics in many cases, restricted pipeline access, and various legal issues. Some of the leading methane capture options under discussion include market-based emission control programs, carbon offsets, emission performance standards, and maintaining existing programs and incentives. At present, methane capture technologies are supported by tax incentives in some cases, by research and demonstration programs in others, by regulation in the case of the largest landfills, and by voluntary programs. Congress could decide to address methane capture in a number of different ways, including (1) determining the role of methane capture in energy and environmental legislation; (2) determining whether methane capture should be addressed on an industry-by-industry basis; and (3) determining if current methane capture initiatives will be further advanced with legislative action regardless of other facets of the environmental policy debate. What role methane capture would play in prospective regulations to control GHGs is among the issues that Congress faces.

Methane removal also improves air quality by decreasing the concentration of tropospheric ozone, exposure to which causes an estimated one million premature deaths annually worldwide due to respiratory illnesses. This is an oft-overlook and an important point which could help to “sell” expensive methane removal to the public and to policy-makers.

General classes of technologies for methane removal include photo-catalysts, metal catalysts associated with zeolites and porous polymer networks, biological methane removal, including industrial approaches and approaches for managing soils in agricultural or other ecosystems, and iron-salt aerosol formation. For each of these technologies, research is needed on its cost, technological efficiency, scaling and energy requirements, social barriers to deployment, co-benefits and potential negative by-products. Research is also needed broadly on methane sorption to concentrate methane from low-concentration background air; having better sorbents would make methane removal technologies more efficient generally. The good news is that all of these technologies could have a passive air-flow, thus rendering them potentially within economic cost feasibility, however this only as long as the atmospheric currents last, so time is of the essence.