![]() The costs may be higher as well, but may be feasible for dealing with emissions from diffuse sources.ĭeep ocean storage will increase ocean acidification, a problem that also stems from the excess of CO 2 already in the atmosphere and oceans. The estimated energy needed for air capture is only slightly more than for capture from large emission sources. It is possible to capture CO 2 directly from the open atmosphere, but this is still being researched. However, the CO 2 produced in the reforming process must also be captured and stored. This process is called methane reformation. A cheaper and more mature option to enable the conversion to hydrogen to be started is to produce hydrogen from natural gas. Whilst hydrogen produced by a process called electrolysis of water using renewable power has very low CO 2 emissions, it is currently expensive. ![]() Source: © SPBer / Wikimedia CommonsĪnother way of reducing atmospheric emissions of CO 2 in some areas, such as heavy goods vehicles, where battery-based electric power is unsuitable, and trains, and domestic heating and gas cookers, is to convert to hydrogen. Finally, the water is condensed and the concentrated CO2 compressed into liquid. The flue gas is treated and sulphur oxide particles and other contaminants are removed. Lignite and hard coal are combusted in a mixture of oxygen and re-circulated CO2, which also contains water vapour. Oxyfuel combustion plant at Schwarze Pumpe, Germany. Whilst it may be the most effective method of the three, the initial oxygen burning process is energy intensive. It is possible that some CO 2 will dissolve in the condensed water, so the water may have to be further treated. The water condenses through cooling and the result is almost pure CO 2 that can be transported and stored.Įlectricity plant processes based on oxyfuel combustion are sometimes referred to as ‘zero emission’ as nearly all the CO 2 is captured. The resulting flue gas consists of mainly CO 2 and water vapour. In oxyfuel combustion, the fossil fuel is burned in oxygen instead of air. It is a cheaper option than post-combustion but cannot be retro-fitted to older power plants. Pre-combustion is used in the production of fertiliser, chemical gas fuel and power production. The process also produces hydrogen, which can be separated and used as fuel. CO 2 can be captured from this relatively pure exhaust stream. First, the fossil fuel is partially burned in a ‘gasifier’ to form synthetic gas. This technique traps CO 2 before burning the fossil fuel. The technology is well understood and is currently used in other industrial applications. This is the method that would be applied to most conventional power plants as it can be retro-fitted. CO 2 is captured (‘scrubbed’) from the exhaust (or ‘flue’) gases. In this process, CO 2 is removed after burning the fossil fuel. Where fossil fuels are burnt at power plants, there are three techniques to remove or ‘scrub’ CO 2: Capture from the open atmosphere is also possible. What are we doing about climate change?ĬO 2 can be captured from large sources, such as power plants, natural gas processing facilities and some industrial processes.Understanding carbon capture and storage. ![]()
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