Dear All, There was a 2007 project in Brazil to eliminate methane accumulated on the bottom of dams. See on the BBC at http://news.bbc.co.uk/2/hi/6638705.stm
"Project aims to extract dam methane" By Tim Hirsch Sao Paulo, Brazil Scientists in Brazil have claimed that a major source of greenhouse gas emissions could be curbed by capturing and burning methane given off by large hydro-electric dams. The team at the country's National Space Research Institute (INPE) is developing prototype equipment designed to stop the greenhouse gas from entering the atmosphere. The technology will extract the methane from the water to supplement the energy produced by the dam turbines. The scientists estimate that worldwide the technique could prevent emissions equivalent to more than the total annual burning of fossil fuels in the UK - and reduce the pressure to build new dams in sensitive areas such as the Amazon. The project follows a long-running controversy over how clean hydro- electric power really is. Critics of the industry have claimed that in tropical areas of Brazil - which supplies more than 90% of its electricity from large dams - some reservoirs emit so much methane that their contribution to climate change is greater than an equivalent power station burning fossil fuels like coal or gas. How the technology will work 'Soda' factor Methane is produced mainly by bacteria that break down organic matter where there is little or no oxygen, for example at the bottom of lakes and reservoirs. Since intake pipes for hydroelectric turbines tend to be placed quite deep, methane-rich water is suddenly transferred from conditions of high-pressure to the open air. The lead scientist of the INPE project, Fernando Ramos, told the BBC's Science In Action programme: "It's like opening a bottle of soda. A large part of the methane is dissolved in the water bubbles, and it's released to the atmosphere. "That's the reason big hydro-electric dams built in tropical areas are harmful to the environment." There is still great uncertainty about the precise amount of methane added to the atmosphere in this way, as each dam behaves in very different ways depending on the amount of vegetation in the water, the temperature, the shape of the reservoir and many other factors. However, a statistical analysis carried out by the INPE scientists has estimated that large dams could be responsible for worldwide annual emissions equivalent to some 800 million tonnes of carbon dioxide. To put that in perspective, last year's total greenhouse gas emissions from the UK were around 660 million tonnes. Partial waters The impact of methane emissions is disproportionate to their actual quantity, since, tonne for tonne, the gas is estimated to be more than 20 times as powerful than CO2 in creating the human-induced greenhouse effect linked to climate change. The INPE scientists are proposing that with relatively simple technology, this unwanted by-product of hydro-electric power generation could be turned into an extra source of clean, renewable electricity. They have estimated that some dams with an especially heavy methane load in the Amazon could increase their output by up to 50%. The first stage of the plan is to prevent deep, methane-rich water from going directly into the turbines, reducing the "soda bottle" effect. A submerged membrane or steel barrier close to the dam would channel surface water to the intake pipes - there is little or no methane at the higher level of a reservoir where oxygen is plentiful. To tap the methane, a floating device would pump deep water to an enclosed rotor on the surface. This would create small droplets that would liberate the dissolved gas, which could then be piped to a plant that would burn it to produce electricity. Technology demonstrator Burning methane does produce carbon dioxide, but since this carbon would have originally been taken out of the air by plants through photosynthesis before being locked into the sediments on the floor of the reservoir, the scientists argue there would be no net addition of greenhouse gases to the atmosphere. It would also prevent the much stronger global warming impacts of direct methane emissions, they say. But the process of extracting the methane would require considerable amounts of energy. However, the team suggest this could be supplied by hydro-power at night when demand is much lower; and in any case, they say, it would be far outweighed by the power generated by the thermal plant. INPE hopes to develop prototype equipment to demonstrate the process later this year. It is sure to be very controversial in Brazil where power companies have been strongly disputing claims that their dams are significant sources of greenhouse gases. Dr Ramos told the BBC: "We cannot hide from this problem; you have to address it. In fact, it's better to recognise there is a problem today, and to use this methane that is there as a commodity, harvest it to produce energy. "And most important, it will reduce the pressure for building new dams in sensitive areas like the Amazon region." See picture on BBC: http://news.bbc.co.uk/2/hi/6638705.stm 1. Reservoir waters are drawn by gravity towards the dam wall and the turbine intakes positioned near its base 2. A membrane preferentially steers higher, methane-poor waters into the turbines to produce electricity 3. A deep pump takes the methane-rich waters to the surface for separation and gas capture in a sealed vessel 4. The methane is stored for burning, to drive a steam turbine and make more electricity. Depleted waters return to the reservoir" Regards Renaud de Richter On 6 oct, 05:44, Stephen Salter <[email protected]> wrote: > 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 195www.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 inhttp://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/Articl... > > > > > [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] > > > > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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