Nov 25, 2012
Thanks for adding this Andrew! Has this been done anwhere? I guess methane isn't a plant nutrient and plants in the greenhouse would be hard to tend/water so this isn't a way to get food? I guess the concentrations wouldn't be high enough to flare so you're planning to concentrate methane and capture as a fuel? If this is intended for land such as peat bogs and permafrost would greenhouses just intensify the warming effect and release more methane faster? Even if the plastic was opaque and reflective you're still looking at covering up to 1m square miles of peat... James
Nov 25, 2012
It's not necessarily agricultural, although there may be opportunities to carry out agriculture/horticulture in the tunnels. Methane would of course require concentration and treatment. It's not clear whether there would be a net warming or cooling effect in the local environment. Snow would tend to cover the polytunnels for much of the year in cold locations. While the interior air would be substantially warmed, convection would be blocked - leading to a potential cooling effect on the wider environment. Additionally, polytunnels can have a higher albedo than surrounding terrain, leading to a potential cooling effect. Tunnels would be placed over active seeps, and are not intended to be deployed at biome-scale.
May 3, 2013
Instead of going to the effort of concentrating the methane in the air, an alternative would be to simply use the air as input to power plants or engines where additional fuel would be added in any case. With fuel being added, that would ensure the potential for combustion of the low level methane as well as the fuel. Or one could perhaps then have the air go through a sewage or waste treatment system from which methane is also being collected, so that the additional methane added would make the concentration high enough to combust or process in a fuel cell. In that the methane is formed under anaerobic conditions, basically meaning too much water and too little air, it would seem that the first thing that should be done under such conditions would be to alter the air/water mixture so that the formation of methane (which must be taking away energy that one would prefer go into crop growth) does not occur. Overall, however, this seems like something only useful on a very local basis and not something that could be scaled to have a significant effect on the concentrations of the gases causing climate change.
May 3, 2013
Much of the flux of methane comes from fairly small areas, consisting of ground seeps and lake margins. Therefore, the area needing to be covered is orders of magnitude less than might be expected. The problem generally with the use of large plant is that methane generally arises across very large areas with little or no habitation. There are no sewage plants or power stations in the vast majority of these areas. Aerating soils and water to reduce methanogenesis and increase methanotrophy is indeed desirable, and is dealt with in other proposals.
Jul 10, 2013
Thank you for sharing your ideas and for the work invested to create this proposal. Your proposal has been considered carefully by the judges, and while the proposal has interesting ideas, and we appreciate the response to questions that were raised, it is unclear how much methane release the scheme would address and whether it could be developed to have a sufficiently large impact.