Carbon capture

Carbon capture refers to measures that at least temporarily remove carbon dioxide from the atmosphere or prevent its release to the atmosphere. One way in which net release of carbon dioxide to the atmosphere is prevented is the use of biomass for fuel and raw material in place of petroleum. When biomass is burned, carbon dioxide is released, but exactly the same amount of carbon dioxide was removed from the atmosphere for the photosynthetic production of the biomass. Therefore, on balance, using biomass as fuel does not add carbon dioxide to the atmosphere. If biomass is not burned or does not decay, its production amounts to a net loss of atmospheric carbon dioxide. 

A tantalizing possibility with respect to the use of biomass fuels arises from the fact that photosynthesis in most plants is only about 0.5% efficient. Increasing this value to even just 1% would 

Biomass added to soil in the form of photosynthetically generated stalk or straw by-products of crop production has the effect of temporarily removing carbon dioxide from the atmosphere. Eventually, most of the biomass incorporated into soil decays and releases its carbon back to the atmosphere as carbon dioxide. However, biomass can be pyrolyzed to release volatile matter leaving a pure carbon residue called biochar. Biochar does not decay and the elemental carbon of which it is composed remains in soil. Biochar is being advocated as a soil additive that retains nutrients and water and sequesters within soil the carbon dioxide produced in the decay of plant matter. The volatile matter released in making biochar contains liquids and gases that can be used as fuel and as feedstocks for chemical synthesis. 

Carbon sequestration is employed to capture carbon dioxide generated in combustion, fossil fuel gasification, and fermentation (such as in the production of bioethanol) and to place the carbon dioxide where it cannot be released into the atmosphere. Carbon sequestration works best with concentrated sources of carbon dioxide. The carbon dioxide from conventional sources where fossil fuels are burned in air is so dilute that its capture for sequestration is challenging and expensive. In coal gasification to produce elemental hydrogen, however, carbon in coal is reacted at high temperatures with oxygen and steam in several reactions for which the overall process is 

The net result is the production of a mixture of equal volume percentage carbon dioxide and elemental hydrogen. The hydrogen product is a premium nonpolluting fuel in applications such as 

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Greenhouse Gas Emissions - Carbon Capture, Storage and Utilisation... 

Carbon capture and storage technology is the most promising technology to significantly decrease C02 emissions. Nevertheless, it may be possible to use C02 as a raw material for other industrial uses. In this chapter, authors explain both ways to decrease C02 emissions. 

In this chapter, authors review the carbon capture, storage technology (including the C02 transport through pipeline), and C02 utilisation technologies. 

The most promising emerging technologies applied to carbon capture are discussed in this section to complete the overview of the C02 capture technologies currently under research. 

This technology shows benefits for carbon capture. Limestone is cheap and widely available, and there is a potential for process integration, which can lead to low energy penalties, i.e., heat released from carbonisation can be utilised in a steam cycle or the heat used in the calciner reactor can be recovered in the carbonation process. 

The combination of a less-constrained ASU for oxygen production and a carbon capture process using membranes instead of amine solvents can conduce to a minimal energy requirement associated with an oxygen purity ranging between 0.5 and 0.6 molar fraction. 

E. Rubin, H. Mantripragada, A. Marks, P. Versteeg, J. Kitchin The outlook for improved carbon capture technology. Progress in Energy and Combustion Science, 38(5). 2012. 

S. Rackley, Carbon Capture and Storage, Gulf Professional Publishing, Houston, USA 2009. 

PiresJ.C.M., Martins F.G., et al. Recent developments on carbon capture and storage ... 

Goel Carbon capture and storage technology for sustainable energy. 2009 Jawahar-lal Nehru University, New Delhi, India. 

Nelson, T.O., P.D. Box, D.A. Green, and R.P. Gupta, Carbon Dioxide Recovery from Power Plant Flue Gas using Supported Carbonate Sorbents in a Thermal Swing Process, Sixth Annual Conference on Carbon Capture and Sequestration, Pittsburgh, PA, May 2007. 

Another integrated carbon capture technology is called the fuel-flexible process developed by General Electric (GE). This process takes different feedstocks such as coal and biomass and produces hydrogen and electricity in adjustable ratios (Rizeq et al., 2002). The reaction scheme for this process involves two chemical loops operated using three fluidized-bed reactors as shown in Figure 17.5. 

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