Carbon Capture

by Keith Heyde

Coal is bountiful, cheap, and accounts for about 50% of our current electricity generation. Worldwide, coal is the dominant source of power and is projected to increase even further as petroleum prices skyrocket.

However, coal is dirty. Along with ash, it is also carbon rich and has an incredibly high ratio of CO₂ output per kWh of electricity generated. This is because the hydrocarbon ratio in coal is very low (about 1C to 1H), meaning more C per bond broken, and consequentially more CO_2.

In an age where concern over greenhouse gasses seems to run counter to free market ideology, what can be done to make coal energy, more appealing?

The answer lies with carbon capture technology.

Carbon capture, and carbon scrubbing, is the technology that goes into cleaning, filtering, and storing the excess CO₂ generated by coal fired power plants.

Already, there are examples of carbon capture that we did not even build. Every plant and algae species are effectively a terrestrial carbon capture machine. They take CO₂ from the air and turn it into stored, organic carbon.

However, with an increase in airborne CO_{2 ,}clearly more than simply trees and algae are necessary to rectify out CO₂ imbalance.

One method of carbon capture is to inject effluent CO₂ into underground caverns. According to a USGS study, closer to 40% of the coal fired power plants within the U.S. lie directly above of potential geological CO₂ storage caverns. This could provide successful areas where we can inject CO₂ underground rather than allow it to enter the atmosphere. This makes ‘dirty coal’ into ‘economical coal’ and a far more attractive option than it is today.

Other Carbon Capture technology seeks to pump CO₂ into existing geological cavities formed from dried oil wells. Yet other tech seeks to crystallize the CO₂ and use the resulting mineral as building material.

As it stands now, CO₂ sequestration technology is not yet commercially viable. Due to the large amount of energy required to pump the gas underground, there is constant research going into how to better perform CO₂ sequestration technology.

This research falls into precombustion and postcombustion categories.

Precombustion alters the fuel source before it is ignited. Often times, this is a gasification process (see gasification article).

Postcombustion is dealing with the CO2 after the fuel source has been ignited. These methods include passing carbon through membrane filters, allowing the CO₂ to be biologically metabolized, using the CO₂ in fertilizer aspects, using CO₂ as an enzyme for catalysis processes or adding CO₂ to landfills for accelerate the carbon cycle.

Existing CO₂ sequestration projects include:

Archer Daniels Midland (IL)

http://www.adm.com/enUS/responsibility/2010CR/environmental_improvement/Pages/carbon_sequestration.aspx

Leucadia Energy, LLC (NY)

http://www.netl.doe.gov/technologies/coalpower/cctc/iccs1/bibliography/iccs_leucadia.html

The cutting edge of carbon sequestration technology includes using the CO₂ for anything from biofuel to concrete production. These include large industrial projects such as Phycal, LLC.

For more on carbon sequestration:

http://www.fossil.energy.gov/programs/powersystems/index.html

http://csite.ornl.gov/

http://www.epa.gov/sequestration/faq.html