What is CO2 Sequestration

Capture


Santa Monica Bay and Beach

Santa Monica Bay and Beach


CO2 capture—the first step in the process of controlling CO2 emissions from industrial sources—involves separating the CO2 from combustion exhaust gases, or in some cases from fuel gases before combustion, at large industrial facilities such as power plants, oil refineries, and cement plants.CO2 capture has been happening for many years in the petroleum, chemical, and power industries, for a variety of reasons relevant to those industrial processes. However, in those cases, only a small portion of the CO2 produced is captured. Capturing all, or even just three-fourths, of the CO2 in a typical power plant with current technology would require equipment many orders of magnitude larger - a very expensive and highly energy-intensive option.Adapting these processes to capture CO2 from large industrial combustion sources is currently the subject of considerable research. In particular, researchers are seeking new approaches to CO2 capture that use less energy, take up less space, and cost less.CO2 capture is generally estimated to represent three-fourths of the total cost of a carbon capture, storage, transport, and sequestration system. In addition, without feasible, cost-effective ways to transport and store the captured CO2, there is no point to capturing it from power plants.

CO2 that is produced by power plants is captured by three main methods: 1) Flue-gas (or exhaust gas) separation removes CO2 with a solvent, strips off the CO2 with steam, and condenses the steam into a concentrated stream. Flue gas separation renders commercially usable CO2, which helps offset its price; 2) Oxy-fuel combustion burns the fuel in pure or enriched oxygen to create a flue gas composed primarily of CO2 and water ; 3) Pre-combustion capture removes the CO2 before it's burned as a part of a gasification process. The most likely options currently identifiable for CO2 separation and capture include:

  • Absorption (chemical and physical)
  • Adsorption (physical and chemical)
  • Low-temperature distillation
  • Gas separation membranes
  • Mineralization and biomineralization

In the United States, 98% of anthropogenic CO2 emissions come from combustion of fossil fuels; consequently, CO2 emissions and energy use are highly correlated.  All forms of fossil fuel electric power plants would be candidates for carbon capture, as the power sector accounts for 40% of total U.S. energy-related CO2 emissions.