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How CO2 Scrubbing Works

Challenges of CO2 Scrubbing
This power plant w­ith scrubbing technology is not only a lot cleaner than regular plants, but also a lot more expensive.
This power plant w­ith scrubbing technology is not only a lot cleaner than regular plants, but also a lot more expensive.
Istock Photo

As with many relatively new technologies, CO2 scrubbing faces its share of challenges. Obstacles depend on the particular process used to remove carbon dioxide and may include degradation of the solvent by other flue gases, corrosion of membranes, reduced adsorption by flue gas impurities, as well as increased energy costs and needs.

At present, the latter two issues tend to be the most problematic. Some analyses estimate that current capture technologies cost around $150 per ton of carbon captured, adding between 2.5 cents/kWh and 4 cents/kWh to your electric bill [source: U.S. Department of Energy]. Other estimates put the price closer to 9 cents/kWh -- an 84 percent increase over electricity purchased from a plant without carbon capture technology [source: U.S. Department of Energy].

Prices vary so widely because a number of factors affect costs, including the design of the scrubbing system, the location of the plant, the efficiency of the plant and whether the carbon capture technology was original or added later. For instance, while electricity generated at a new coal plant using CO2 scrubbing may cost 57 percent more than electricity generated in a plant without carbon capture, electricity generated at an existing plant retrofitted with CO2 scrubbing can cost up to 290 percent more [source: Williams].

In addition to being costly, CO2 scrubbing also requires a lot of energy. Not only does it require treating a high volume of gas (remember that only a small percentage of flue gas is actually CO2), but it has to compress the captured CO2 into a storable form -- a very energy-intensive process. So, ironically, capturing carbon actually ends up using its own share of fuel. New coal plants fitted with carbon capture may use anywhere from 24 to 40 percent more fuel than those not fitted with the technology, while retrofitted coal plants may use up to 77 percent more [source: Williams].

­­ Even taking into account its own energy usage and emissions, though, CO2 scrubbing still removes a net amount of 80 to 90 percent of the carbon dioxide from flue gas [source: GreenFacts]. That's a good thing, since some scientists estimate our emissions of CO2 may need to be reduced by 60 to 80 percent to avoid catastrophic climate changes [source: Marion]. Next, find out about the applications for CO2­ scrubbing.