User:Andrewjlockley/methane geoengineering

Background LeLieveld et al (1998) state that: Methane concentrations have increased from about 0.75–1.73 μmol/mol during the past 150 years to date of paper; ~70% of the total source is anthropogenic; methane accounts for 22% of the radiative  forcing by all long-lived greenhouse gases (2.6 W m−2) ; GWP is 21 (kgCH4/kgCO2) over 100yr However, the GWP of methane has probably been underestimated.(Shindell et al, 2009) The paleoclimatic record implies the possibility of dramatic warming in the Arctic in response to AGW http://www.micropress.org/stratigraphy/papers/Stratigraphy_6_4_265-275.pdf Dickens et al (1997) note that “Gas hydrates in oceanic sediments may in fact comprise the Earth's largest fossil-fuel reservoir. But the amount of methane stored in gas-hydrate and free-gas zones is poorly constrained.” Reagan & Moridis (2008) note that “shallow deposits can be very unstable and release significant quantities of methane under the influence of as little as 1°C of seafloor temperature increase” However, Lamarque, predicts. “Using an observed 1% ratio to estimate the amount of methane reaching the atmosphere, our analysis leads to a relatively small methane flux of approximately 5–21 Tg(CH4)/year”. Archer (2007) notes “The hydrate reservoir is so large that if 10% of the methane were released to the atmosphere within a few years, it would have an impact on the Earth’s radiation budget equivalent to a factor of 10 increase in atmospheric CO2”

Permafrost environments within the Siberian Arctic are natural sources of methane. The paleoclimatic record indicates a significant role for abrupt methane excursions in major climatic events such as the PETM (Schmitt & Shindell, 2003) and the P-T Mass Extinction (Krull & Retallack, 2000). Atmospheric methane is naturally broken down by oxidation, ultimately to water and carbon dioxide. This oxidation process is primarily conducted by reaction with OH radicals (GHANSHYAM L. VAGHJIANI* & A. R. RAVISHANKARA, 1991) Introduction Herein is set out possible treatments for: 1)	Unstable methane reservoirs (including frozen organic detritus), 2)	Aquatic methane production and excursions 3)	Concentrated atmospheric methane 4)	Diffuse atmospheric methane Treatment methods are rated by estimated scale of practicable application as 1)	‘limited’ – able to treat some excursions 2)	‘significant’ –climatically significant capacity 3)	‘full’ – able to manage the entire methane budget Treatments are assessed against the following criteria: 1)	Infrastructure/implementation cost 2)	Energy cost 3)	Expected efficacy 4)	Development cost & uncertanties 5)	Environmental impacts 6)	Potential for CCS A ranking is given simply of ‘positive’, ‘neutral’ or ‘negative’ in each category, with accompanying commentary. Rankings are a matter of personal judgement and are used to crudely rank proposals. An asterisk marks outliers. The intention of ranking the treatments is simply to highlight proposals worthy of further study, and is not set out as fully considered analysis. 0: - SRM geoengineering The potential use of geoengineering techniques such as Cloud Condensation Nuclei  and Stratospheric Sulphur Aerosols is widely acknowledged.  Such techniques may be regionally or globally applied, and thus can contribute to cooling and hence stabilising methane deposits.  Further, these techniques may additionally have a role in cooling the planet in response to a sudden warming caused by an excursion of methane into the atmosphere.  The opportunities to employ such techniques is the subject of ongoing research,  For comparison, the use of these techniques to react to a large flux of methane is evaluated below, using the same rating scale. We conclude the scale of the technique to be ‘full’, considering the work of Robock

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	0	-1	-1	0 Moderate deployment costs	Low ongoing energy requirements	Potential to counter warming without allowing enhanced remediation	Costly to develop and test at scale. Possible climatic disruption	None Score = -3	Scale = Full

Section 1 - Pre-emptive treatment of methane reservoirs Unstable reservoirs of methane may be mined, or otherwise treated to initiate controlled release of methane for collection and treatment.

Soil heating Excursion of methane from soil and mire is seasonal, and is temperature dependent. Soil temperature may be raised to hasten the excursion and permit collection and treatment. Soil Heating using Polytunnels Agricultural 'polytunnels' create warmed microclimates, which may be used to trigger excursions into the contained tunnel environment. Depending on extraction timescales, equipment re-use is possible.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	-1	1	-1	-1 Large treatment area, long timescales	Economic recovery unlikely 	Slow, leaky. Simple to construct and test. Widespread disruption to ecosystems. Low concentrations.

Score = -3	Scale = Significant

Soil heating using heat pumps Active or passive heat pumps may be used to warm soils and mires. Energy from warmer soils and water bodies, or from solar heating, could be used as the heat source. It may be possible to extract methane from deep permafrost while shallower layers serve as a cap.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	1	1	-1	-1 Large treatment area required	Renewables, possible recovery	Reasonably effective recovery from limited areas may be possible. Inexpensive to test and trial	Major ecosystem disruption. Volumes too low and locations too remote to allow CCS Score = -1	Scale = Significant

Soil aeration Physical treatment of the soil to enhance aeration may be possible (e.g. ploughing). This may cause decomposition of organic matter to occur in an oxygen-rich environment. However, it may simply stimulate the excursion of methane, and further research is needed.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	0	1	-1	-1 Large area required	Operations require little energy, other than tractor fuel	Unproven. Treats surface layers only. Inexpensive to test and trial	Large scale mechanical processing needed. Impossible Score = -2	Scale = Significant

Mining clathrates Established proposals exist for the commercial mining of methane clathrate as an energy source. At cost, this may be extended to uneconomic deposits.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture 1	1	1	1	1	1 Economic recovery possible	Concentrated energy source	Highly effective at treating concentrated deposits. Already under consideration without subsidy. Mostly limited and localised impacts, save leakage and landslide. Ideal for capture

Score = 6	Scale = Significant

Burning of clathrates In clathrate deposits where mining or other recovery is impractical or uneconomic, controlled or partially-controlled releases for burning may be initiated. Disruption of clathrates could be done by heating, blasting, or the use of machinery. Burning could be performed at the surface as detailed above. Alternatively, underwater burning could be oxygenated with piped air, either within submersible plant, or possibly in open water.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	0	-1	1	-1 Significant and complex engineering, often at depth, without recovery	Minimal energy consumption	Depends of containment efficacy	Requires significant development, with no economic benefits	Mostly limited and localised impacts, save possible shelf collapse	Capture likely impractical at scales uneconomic for mining.

Score = -2	Scale = Significant

2: Aquatic methane production & excursions . Methane fluxes to the atmosphere from lakes are principally by ebullition (bubbling) from thawing shoreline permafrost. Larger bubbles, and those released from shallow deposits may reach the surface and deposit their methane load into the atmosphere.DOI_CAN Aqueous solutions of methane are typically biodegraded before reaching the atmosphere.DOI_CAN

Lake sealing

Covering lakes with an airtight seal will prevent methane fluxes to the atmosphere. Non-biodegradable foaming agents could be used to trap methane bubbles in a stable layer. Burning or collecting the foam is then possible. In shallow lakes a miscible foaming agent could be used, but in deeper lakes an oily foaming agent could be floated on the surface, This technique would severely affect the oxygen supply, and thus tend to create further methane by forcing anaerobic respiration to dominate. Aeration equipment could be used to avoid the collapse of the lake ecosystem.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	1	1	-1	0 Large treatment area, ongoing maintenance	Energy recovery difficult	Reasonably effective containment possible	Simple to test and trial	Blanket coverage of lakes required	Potentially possible in larger lakes

Score = 0	Scale = Significant

Mixing of aquatic strata Methane bubbles may dissolve into the water column, with shallow releases having much higher chance of entering the atmosphere. Geoengineering techniques for mixing ocean strata have already been proposed. Water mixing may promote methane dissolution by means of temperature adjustment, downwelling and gas concentration adjustment. Smaller bubbles are relatively prone to dissolution due to their surface area and ascent time. Mixing equipment may cleave bubbles, aiding dissolution. Enhanced flow rates on sea and lake floors may encourage the cleavage of smaller bubbles from gas reservoirs.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	1	-1	1	0	-1 Treatable area uncertain, subject to ongoing research	Established technology has been proposed for mixing using wind/wave energy. No evidence the approach will work. Simple, low technology testing. Some disruption to ecosystems may occur. Effects likely local & limited. Impractical

Score = 0 	Scale = Significant

Bubble capture Funnelling bubbles into capture pipework may be practical. As an alternative to capture, the funnel may be perforated to release small bubbles, aiding dissolution and aquatic methantrophy. Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	1	1	1	0	1 Costs depend on concentration of sources	Net energy source, although economic recovery may not be possible	Potentially very effective for locally concentrated aquatic excursions. Easy to prototype	May disrupt marine ecosystems. Could disrupted upwelling/downwelling currents	Concentrated gas could be collected and transported to CCS plant.

Score = 4 	Scale = Significant

Water aeration Successful oxygenation of anoxic waters and sediments facilitates aerobic methanotrophy, which is a significant factor in the local methane budget. . Oxygenation also impedes methanogenesis. Aeration technology using bubblers and impellers is widely studied and implemented, e.g, including cold water systems

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	-1	1	1	-1 Large numbers of lakes require treatment	Renewable power readily available	Unproven. Mixing may not penetrate anoxic sediments and/or aquatic strata. Widely commercially available	Low impact on most ecosystems	Impossible

Score = 1	Scale = Significant

Biological oxidation in aquatic environments Aerobic metabolism of methane could be enhanced by depositing or fertilising methanotrophs, where their relative absence limits metabolism. The concurrent distribution or fertilisation of autotrophic flora (e.g. phytoplankton) may additionally benefit by enhancing oxygenation, although consideration must be given to preventing consequential eutrophication. This technique partners with mechanical aeration.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	0	-1	1	1	-1 Continual resupply of active organisms required. Distribution /manufacture energy only	Unlikely that existing microorganisms can be significantly enhanced. Relatively cheap to test with non-GMO organisms. Significant ecosystem damage unlikely. Impossible

Score = 0	Scale = Significant

3: Remediation of concentrated atmospheric methane . In some areas, concentrations of atmospheric methane are occasionally so high that it forms a flammable fuel-air mix at small scales DOI_CAN. This opens up the possibility of an ignition-based oxidation process in appropriate areas.

Regenerative Thermal Oxidation Reverse-flow regenerative thermal oxidation plant is widely available commercially It is well tested for a variety of gases. The lower limit of self-sustaining operation is ~0.1-0.2% vol,  This is significantly lower than the concentration limit for flammability, but far higher than the current ambient concentration. Plant or intake pipe would be sited adjacent to excursions.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	1	1	1	1	0 Significant cost to install at scale	Recovery viable	Proven efficacy in correct concentrations	Based on established technology	Proven and benign in operation	Sensitive to concentration.

Score = 3	Scale = Significant

Electrical ignition Small sparking devices that sit atop lakes, seas and soils can be manufactured using vehicle spark plug technology. Robust construction is required to withstand the heating and blast effects. The low electrical power requirements could be provided by micro-renewables, typically located outside the blast area. Distribution could be manual, mechanical or air-dropped. Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	0	-1	1	0	-1 In some specific areas may be relatively inexpensive	No overall impact, save manufacture/delivery	Limited efficacy and only in certain areas	Based on established technology	Causes frequent explosions	Impossible

Score = -1	Scale = Limited

Thermal ignition using incendiary munitions

Very large excursions of methane can potentially occur as a result of the breakdown of clathrate deposits. Detection of natural excursions may be possible using satellite, surface or airborne monitoring. Thermal ignition of the resulting concentrated plumes is possible using incendiary munitions fired from air, surface vessels or field artillery. Existing medium-calibre artillery has a range of 40km, therefore shorelines, shelf edges and other linear features may be flared with no more than 25 guns per 1000km, even allowing for substantial overlap to give a belt of coverage, capacity for ignition at altitude, & redundancy.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	0	-1	-1	1	-1 Somewhat costly, especially offshore	Neutral	Partially-effective treatment of last resort for large fluxes	Monitoring and control a significant challenge	Explosions will typically take place well above ground level	Impossible

Score = -2	Scale = Limited

4: Diffuse atmospheric methane Rarified methane will oxidise if heated. Catalysts allow remediation at temperatures as low as 500C and concentrations as low as 0.2% (Lee, 2006)  All techniques below can be used on concentrated or diffuse sources.

Thermal oxidation by concentrated solar power Concentrated solar power is able to drive the temperatures needed for thermal oxidation of methane, even when rarefied in the atmosphere. Such plants are also able to generate electricity on site, which will give the mechanical power needed to drive the necessary fans and steer the mirror arrays. Heat imparted into the air can be recovered by means of a boiler, like that in a power station. It may be more efficient to use the CSP plants to warm a heat-exchanger fluid to avoid the need to heat air directly, although losses will occur as a result of the transfer process. Further research on efficiency losses is required. Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	0	1	1	1	0 Efficiency costs requires extra plant	Process efficiency reduced significantly	Complete treatment of limited volume	Cheap to build test plant	No impact, other than increasing CSP plant area. Uses ambient air Score = 3	Scale = Significant, (full with dedicated plant)

Thermal oxidation by waste heat Where high-grade waste heat is available, heat exchangers may be used to transfer this heat to air, potentially in the presence of catalysts. Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	0	1	1	1	-1 Typically requires expensive catalysts	Uses waste heat	Effective treatment of limited volume	Cheap to build test plant	No impact, especially if NOx catalysed. Distributed, small sources. Score = 1	Scale = Limited

Compression ignition Diesel engines heat air by compression to achieve thermal ignition. By designing engines with sufficient compression ratios, spontaneous oxidation of atmospheric methane can be achieved. Modified vehicle engines driven electrically when not in use could be employed, and the possible future generation of plug-in hybrids makes this possible at useful scale. Unmodified jet engines typically have higher compression ratios. NOx is a climatically-useful (although toxic and environmentally harmful) by-product of compression heating, which can be catalytically mitigated if required. Energy expended in compression is partially recovered during expansion, and can also be recovered by heat exchangers acting to cool the pressurised gas. However, frictional and heat transfer losses are inevitable. Dedicated plant could be developed with vast, insulated cylinders or similarly-designed jets, to minimise losses. Such plant may benefit from catalysts to enhance methane oxidation, which are unlikely to be suitable for use in working engines. Cost	Energy	Efficacy	Development	Environmental	CO2 capture -1	-1	1	1	-1	-1 Requires modification of global vehicle fleet or dedicated plant	Frictional & thermal losses, vehicle efficiency issues	Complete treatment of treated volume	Cheap to build test plant	Increased engine wear and early scrapping. NOx. Uses ambient air Score = -2	Scale = Full

Chemical degradation Degredation of methane by hydroxyl radicals is the primary fate of atmospheric methane at present. ((VAGHJIANI & RAVISHANKARA, 1991), 1991). OH lifetimes in the atmosphere are of the order of seconds, and point injection of OH radicals are therefore unlikely to mix well. Raising concentrations of photochemical precursors to OH may be more successful. The principle natural method for the creation of OH radicals is the photolysis of ozone (itself a GHG). Ozone may be manufactured at high energy cost and injected directly. A lower-energy method is the manipulation of ozone precursors, including NOx, which catalyses the ozone production photochemistry cycle. NOx emissions lead typically to a net negative radiative forcing effect by this method. NOx is evaluated below.

Cost	Energy	Efficacy	Development	Environmental	CO2 capture 0	0	1	0	0	-1 Moderate investment in plant	Chemical manufacture. High with correct design	Development at scale possibly costly. Potential damage to atmos. chemistry	Diffuse Score = 0	Scale = Full

Conclusion There is no one technique which offers a ‘magic bullet’ to the problem of atmospheric methane, as all solutions detailed have potential or identified major drawbacks or limitations of scale. However, cheap, simple research can be carried out to test most proposals. Higher-scored and fuller-scale techniques merit further detailed study.