The fight against the greenhouse effect becomes an industrial reality. Now that the optical to bury the CO2 underground ("Les Echos" of yesterday) is realistic, for large emitters are working hard in the capture of this greenhouse gas. For years, is known to separate CO2 from flue gases of combustion, but costs remain prohibitive, since it increases the electricity bill from 2 to 4 just cents per kilowatt hour. The offices of the producers of electricity, the steel, cement or their equipment thus explore many technologies to make compatible carbon sequestration economically. For the moment, none of the options in this technological portfolio stands, each progressing to its rhythm.
From the Intergovernmental Panel on climate change (IPCC), the technologies allow to capture 90 of dioxide fumes, but experts have calculated that the capture and storage requires 15 to 30 of energy, in particular in the case of storage in the carbonates. In total, can thus theoretically "a net reduction of 85", believes the IPCC. In reality, the countries participating in the CSLF (Carbon Sequestration Leadership Forum) forum hope to reduce emissions of CO2 by 18 by 2012.
Capture is economically the most crucial step, because it represents about 70 of the costs of elimination of dioxide. Strategies to achieve this vary the rate of the CO2 concentration and the State in which it is located. According to specialists, the ideal is to achieve high volumic concentrations, for at least 15, and high pressure. So that the technique of seize dioxide concentrated less than 5 in the smoke in Afterburner is the worst. Yet, this is one that holds the more efforts because it could be applied to existing plants.
Rethinking the combustion
The current solution has been developed by gas to separate the CO2 methane, with which it is naturally mixed in deposits, content of natural gas is regulated. The flue gas is brought to boiling through remover, an amine which absorbs the CO2. The solvent moves by a regeneration unit where it is separated from the dioxide. This method continues to progress at the level of amines, but themselves solvent regeneration. Other approaches rely on the uptake by solid, carbonation-décarbonation or filtering in a microporous membrane. The Beaver launched in 2004 program, four years to develop technologies for the capture and storage of 10 of CO2 emissions in Europe.
But the greatest challenge, particularly in Europe, concerns the replacement of coal and oil power plants. By rethinking the whole of the combustion process, industrial feel able to capture more than 80 of CO2 emissions from thermal plants, with a reduced cost of half the current technologies. The forecast is more conservative on the IPCC, table on a decline of 20-30 within a few decades.
The strategy is this time to work at high concentration by oxy-fuel, i.e. a combustion using pure oxygen instead of air as oxidizer. The CO2 is then easier to separate from water vapour with which it is mixed. The difficulty of the process is then upstream the separation of oxygen air. On these techniques, the French laboratories are very advanced, especially for Alstom, which develops technology "chemical looping" using metal oxides in the production of oxygen.
The third option, in the longer term, is the most ambitious, but also the most promising. It consists of isolating upstream of the combustion of fossil fuels or biomass gas CO2. While in this phase are the best conditions of pressure and concentration. As this method is embeddable in the methods for the manufacture of hydrogen, promised as the vector of energy of the future. Europe and the United States have seized this opportunity in launching this year two ten-year research programmes and funded by more than 1 billion euros each.