Posts Tagged ‘Carbon Capture’

Carbon Capture and Storage (CCS)

The modern era of development, since the industrial revolution, has been fueled by cheap reliable energy sources, namely coal.  Coal is responsible for nearly 50% of US electricity. Coal however, is also the largest emitter of CO2.   With over 1/3rd of the world’s population living in two of the world’s most rapidly developing countries, China and India, the next generation of development will demand (and IS demanding) a cheap reliable source of energy (Chu, 2010).  To achieve the growth that these economies demand, coal will be necessary for the immediate future.  While investment in renewable energy sources should continue, figuring out ways to make coal more environmentally friendly is the key to achieving equitable and sustainable development.

Coal fired electricity generating plants are the biggest emitters of carbon dioxide.  The most direct method of capturing carbon is to capture it before it enters the atmosphere, right at the source.  There are several methods of achieving this goal.  Further details can be found here.

Post-Combustion: This is the traditional model of CO2 capture.  The combustion of coal produces smoke that is laden with CO2.  Extracting CO2 from this smoke can be achieved by either a physical or chemical mechanism.  The physical mechanism acts much the same way as a traditional “scrubber” that removes sulfur and particulate matter from the smoke.  The second mechanism for removing CO2 from the smoke involves a chemical reaction.  By forcing the CO2 smoke through an “amine” solution, CO2 binds to chemicals in the solution.  Once this solution becomes saturated with CO2 it is then ready for storage.

Pre-Combustion: This involves removing CO2 before it undergoes combustion.  Using high pressure and temperatures, fossil fuels can be disassociated into two parts, hydrogen and carbon monoxide.  The hydrogen is then used as a fuel, while the CO is converted to CO2 and is then ready for storage.  This process in energy intensive and is therefore less economically viable for production; however it may become more attractive if hydrogen fueled technologies become more prevalent.

The effects of carbon dioxide as a Greenhouse Gas have been understood for over 150 years.  While it is harmful in high atmospheric concentrations, CO2 itself is an inert gas.  Under moderate pressure it can easily be stored and transported as a liquid.  (The US National Renewable Energy Lab has compiled a nice set of resources).  It is in this liquid form that CO2 can then be stored.   The critical issue with storing COis that the margin of error is razor thin.  The stored carbon needs to be trapped for thousands of years.  At this time scale, even a minor leak of 0.1%/year becomes devastating, as it would evacuate the entire reservoir in 1000 years.  With these margins, high precision monitoring becomes crucial which further increases the cost of CCS.

Carbon Capture technology removes 80-90% of CO2.  However, current carbon capture methods reduce energy output by about 30%.  This means that 30% more coal will need to be burned in order to maintain the same energy output while at the same time still releasing some carbon into the atmosphere.  While this results in less total pollution for the atmosphere, the carbon savings are partially offset by the additional pollution and emissions from the mining and transportation of the extra coal.  Additionally, there is a chance of the carbon being released during transport or storage.  There are many issues at play when it comes to Carbon Capture and Storage, but it is possible, and it is necessary.  The technology will continue to advance and the price of that technology will contine to fall.  CCS will be a crucial step in the path toward carbon neutral growth, as coal will be an integral part of the global energy portfolio for the foreseeable future.

Is CCS feasible? Yes it is feasible, but it comes at a cost.   And unless we start valuing the price of our planet nearly as much as we value of our energy, we’re bound to lose both.