Hi Steven, I think what needs to be decided is the approach:
1) are we trying to address spot-like emissions, or, 2) methane haze arising smoothly from vast area of sea bed. No. 1 can be addressed by a cupola-like hood over the spot from where the gases are removed No. 2 can be addressed by a slightly V-shapedly folded straps of plastic where gas accummulates to the tip of upside down V-fold and steams towards the rising end of strap where it is collected. I think flatbed sheet probaly oozes gas out from over the edges, or one ends up with a controured sheet of multiple gas bubbles; this becomes increasingnly unstable system as gas accummulates. I favour passive systems where gas constantly streams upwards to the collection point. I also think that I roll could be unwound from the back of ship. However, just 1 km2 area with 10 metre strap plastic would require 100 km of sailing back and forth before all is covered. If 100 km x 100 km box was covered from ESAS by sheet 100,000 km of 100 metre strap would be needed. Anoxic conditions can be addressed by say using 2kW Mixox units that could blow 1,000,000 m3 of oxygenated air under the plastic sheet to aerate the plastic covered ocean. Mixox would suck oxygen rich surface air and blow it through tube to beneath the plastic sheet. As methane bubbles are lighter than even oxygenated and less saline surface air, the bubbles would still rise normally through the treated water until they reach the collecting sheet. We proposed with Matti Lappalainen at the World Water Week in 2006 to oxygenate the Amazon river estuary during the low oxygen drought season with 40,000 Mixox units for 100 km section of Amazon in our paper "Preparing the Amazon Ecosystems for the Changing Climate". Mixox systems are deployed in 27 km2 sea floor oxygenation pilot project in the Baltic Sea in Finland and another 2.7 km2 in Sweden to reduced the anoxic conditions arising from warmer temperatures, phosphathe leaks and organic material load. I forward this to Matti as he may have some latest results from the pilot projects. In the Baltic Sea anoxic conditions result mainly from phosphate, although organic loads and higher water temperatures (i.e. the Gulf of Bothnia has seen mean sea temperature to rise +6C). There is no problems of methane arising from the Baltic Sea's sea bed, Mixox has only been deployed to rectify the lack of oxygen. I think Mixox at 1,000,000 m3 and 2 kW is right system to flush air under the plastic cover. Furthermore, the oxygen put under sheet will not excape it is either consumed by methane eating bacteria or other processes. Even mere aerating the sea might work to increase methane eating bacteria to reduce methane leak to air if there is a problematic build up of undigested methane in water that may start to nucleate. It could be that such water could be part oxygenated by Mixoox of Lappalainen, part ventilated by system developed by Michel Halbwachs whichever suits best for a situation; i.e. if the collection of gas for disposal is difficult Mixox needs only electric wire, or even solar panel or wind turbine to run (these have not been looked at as power points are not the issue in the Baltic Sea, unlike the Arctic Ocean). The other issue is to develop some minimum/maximum values for deployment to do it economically and efficiently, rather than scattering equipment across vast areas of ocean that are poorly attended and maintained. There has to be the minimium value / distance to service for each spot where GHGs are leaking out of the melting methane clathrates. If two sites are close by, they may be serviced togheter, so a lower collection threshold is required. If power point is closer, also a lower threshold for methane caption may be required. For sea area methane haze minimum per area must be established as all sea floor leaks out some amount of methane, what is the action threshold? Note that the large water body Mixox systems for the Baltic Sea will blow down much more areated water than the pilot systems. Kind regards, Albert Date: Thu, 6 Oct 2011 10:44:25 +0100 From: [email protected] To: [email protected] CC: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected] Subject: [geo] Re: Arctic methane workshop: 15-16 October - Methane vents Albert If there is a pipe connection to the underside of the plastic the pressure below the film will be close to atmospheric and it will be clamped firmly down by several bar of water pressure. I can also get some sand over the film. I am more concerned about anoxic conditions of which I am totally ignorant. Gases can come up from below. Maybe we could get a film with some oxygen permeability. But if there is oxygen there now why is there any methane? I was going to design for 0.15 metre per second sea bed current. Would you recommend any other value? I am working on a way to recover the film later. Stephen Emeritus Professor of Engineering Design Institute for Energy Systems School of Engineering Mayfield Road University of Edinburgh EH9 3JL Scotland Tel +44 131 650 5704 Mobile 07795 203 195 www.see.ed.ac.uk/~shs On 05/10/2011 18:58, Veli Albert Kallio wrote: We need to consider carefully the plastic film, this could cause anoxic conditions under the plastic sheet. The shallow portion of Arctic Ocean is likely to develop large storm surges and resulting currents as ocean becomes ice free. Every storm surge on surface is maintained by reverse flow on bottom that could pile up any plastics and cause hazards. Funnelling can only be considered for spot like emissions, not if methane bubbles over large areas. The difficulty will be how to cope with monitoring and controlling if there will be thousands of sites where methane is collected that are sparsely distributed. Maintenance is a challenge. > Date: Wed, 5 Oct 2011 10:31:28 +0100 > From: [email protected] > To: [email protected] > CC: [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected] > Subject: Arctic methane workshop: 15-16 October - Methane vents > > > Dear Professor Westbrook, > > Thank you for your response about the width of the shelf margin. > Stephen Salter is working on a method using large plastic sheets to > funnel the methane bubbling up from across an area of the sea bed into a > concentrated stream, and then capturing it. But of course this > funnelling can occur naturally, as one can see from the hundreds of > underwater plumes that you have detected arising from the seabed of the > West Spitzbergen continental margin [1]. Am I right that, at present, > few of these plumes are reaching the surface? Is this because the water > is sufficiently oxygenated for oxidation to occur within the water > column? Is there a danger of this oxygen getting used up? But, if > oxidation does continue, isn't there a danger of excessive ocean > acidification, given the quantities of methane? > > Do you have any suggestions for how one might deal with the methane > rising in a plume, to minimise the various associated hazards: > greenhouse gas warming if it reaches the surface, deoxidation of water > making it sterile, acidification of the water disrupting the marine food > chain that relies on shelled creatures, etc.? > > Best wishes, > > John > > Tel: +44 20 8742 3170 > Skype: john.nissen4 > > P.S. I want as much brainstorming done before the meeting as possible, > especially to involve people who might not be able to attend in person. > > [1] http://eprints.soton.ac.uk/64607/1/2009gl039191%2Baux.pdf > > --- > > On 03/10/2011 18:03, John Nissen wrote: > > > > Dear Professor Westbrook, > > > > A workshop has been arranged on the weekend 15-16 October in Chiswick, > > London W4, to see how to tackle the Arctic methane problem - in > > particular how to prevent large quantities of methane reaching the > > atmosphere and aggrevating global warming. For some years it has been > > apparent that there is vast quantity of carbon locked up in > > permafrost, which is liable to be released as methane as the Arctic > > warms [1]. Global warming potential of methane is high but lifetime > > is short, so the speed of discharge is very important to know. > > Unfortunately recent evidence suggests that the Arctic warming is > > accelerating, the Arctic Ocean could be seasonably ice free within a > > few years, and there is already much methane venting taking place. > > Therefore the situation appears extremely dangerous, and it is vital > > that some plan of action is developed as quickly as possible. That is > > the basic reason for the workshop. > > > > We had originally planned for the workshop to concentrate on the > > methane from the East Siberian Arctic Shelf, ESAS, since Shakhova et > > al claim that up to ~50 Gt of methane could be released "at any > > moment" [2], e.g. if there were an earthquake (and the ESAS contains > > an earthquake zone). However just in the last few days, I have seen > > reports of high levels of methane in the upper atmosphere which could > > have originated from shelf margins, and I came across a paper you > > co-authored [3]. > > > > I would be extremely grateful if you could come to the workshop, even > > if only for part of one day (preferably Saturday 15th), to discuss > > your work on the methane from shelf margins, which I see is one of > > your main research topics [4]. > > > > One of the main contributors to the workshop is a brilliant engineer > > and inventor, Professor Stephen Salter, who has some ideas for > > capturing methane underwater. He needs to know the conditions of the > > shelf margins and distribution of venting over the field. For > > example, what is the typical width of the shelf margin where the vents > > occur? In the paper [3], it is mentioned that 900 Kg of methane may > > be emitted per metre of length of the shelf margin, but over what width? > > > > Working in regions where there is sea ice is going to be a challenge, > > so we have an expert on sea ice, Professor Peter Wadhams, coming to > > the workshop. He is particularly concerned about the sea ice volume > > decline, where the current trend suggests a zero volume for September > > 2015 [5]. > > > > BTW, some time ago I had asked Euan Nisbet to come to the workshop, > > but unfortunately he is unable to attend. So I had been looking to > > the PERGAMON project, and Jens Greinart, with his knowledge of natural > > gas venting. It now appears that he might not be able to attend > > either. So your experience from the PERGAMON project could be very > > valuable at the workshop. > > > > I apologise for the extremely short notice, but I look forward to > > hearing from you. > > > > Kind regards, > > > > John (Nissen) > > > > College House, > > Chiswick Mall, > > London W4 2PR > > > > Tel: 020 8742 3170 > > Mob: 07890 657 498 > > > > [1] http://www.aibs.org/bioscience-press-releases/resources/Schuur.pdf > > > > [2] Reported in http://en.wikipedia.org/wiki/Arctic_methane_release > > > > See also [2a] http://www.sciencemag.org/content/327/5970/1246.short > > and [2b] > > http://earth.usc.edu/ftp/lund/BERING%20SEA%20EXP%20323/Uservol/Articles%20of%20interest/Eurasian%20Basin/Shakova%20and%20Semiletov%202007.pdf > > > > [3] http://eprints.soton.ac.uk/64607/1/2009gl039191%2Baux.pdf > > > > [4] http://www.birmingham.ac.uk/staff/profiles/gees/westbrook-graham.aspx > > > > [5] http://neven1.typepad.com/.a/6a0133f03a1e37970b015433129b3e970c-popup > > > > --- > > [snip] > > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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