Carbon Sequestration Could Be Employed
Today To Help Alleviate Greenhouse Emissions
Columbia University researcher presents "A Guide to CO2 Sequestration"
Recent congressional support to research and develop zero-emissions plants and hydrogen fueled vehicles is a necessary long-term solution toward reducing harmful greenhouse gases; however, there are immediate opportunities to render fossil fuels—currently accounting for 85% of all commercial energy—environmentally acceptable.
“The consequences of global warming are not decades away—they are now. We need to pursue every technological avenue that holds a reasonable promise of clean, cheap, and copious energy, from solar energy to fusion to continued but clean reliance on fossil fuels. By taking advantage of the resources and systems that we have today, we can immediately address the problem of greenhouse gases and enable a smoother transition into new technologies of the future,” said Klaus Lackner. Lackner is the author of a recent “Perspective” in the journal Science describing opportunities to capture and store CO2, while maintaining a reliance on fossil fuels until the transition to zero-emissions and hydrogen fuel can be made. Lackner is a scientist with The Earth Institute at Columbia University and the Ewing-Worzel Professor of Geophysics, Department of Earth and Environmental Engineering.
Lackner’s research shows that it is feasible to render fossil fuels environmentally acceptable. In Science, he outlines a number of ways in which CO2 can be captured (from the power plant point of emission and from the atmosphere), neutralized, and safely and permanently stored. There are many options for storing CO2. Some options, like injection into the ocean, do present their own environmental dilemmas. Oceans are limited in their absorption capacity and because deep water eventually surfaces, the CO2 would escape. Other options, such as underground injection, which is currently used for enhanced oil recovery, are naturally limited in scope. While underground storage of CO2 is a good way to start, Lackner argues that such storage capacity is likely to be inadequate or rely on reservoirs that are not sufficiently stable, posing, for example, a leakage problem that future generations would be left to deal with.
Lackner presents a more permanent method of CO2 disposal through neutralization in carbonate form. This could be accomplished by injecting CO2 into alkaline mineral rich layers of the Earth. When exposed to alkaline minerals, CO2 gas reacts with the alkaline mineral to form carbonates or bicarbonates. Another option is to mine, crush, and react rock that is rich in magnesium silicates with CO2 to form insoluble carbonates. Although this latter method is still more costly, it “would enable above-ground mineral sequestration that has the capacity of binding all CO2 that could ever be generated and limiting the environmental impact, including terrain changes, to relatively confined areas.”
In order to sequester CO2, you must first capture it. Lackner points out that it is best-captured at large plants. The cost of retrofitting existing plants, however, appears to be too expensive, but radically new power plant designs are in the future, starting with the FutureGen plant suggested by the Department of Energy. Lackner suggests that gasification processes involving steam and lime could be incorporated into power plants that generate either electricity or hydrogen while collecting the carbon dioxide in a concentrated stream. Such processes could be extremely efficient. The Zero Emission Coal Alliance has laid out a plant design that could achieve 70% conversion efficiency with zero emissions, as compared to today’s coal-fired power plants that are 30 to 35% efficient with full emissions.
Emissions from cars and airplanes must also be captured. Because these vehicles would never be capable of carrying back their emissions (CO2 is three times as heavy as fuel), once emitted, CO2 would have to be extracted from the atmosphere. Lackner suggests allowing wind to carry emitted CO2 over apparatuses containing chemical sorbents that would capture it for later sequestration. Because the atmosphere mixes rapidly, these apparatuses could be located in remote areas and still compensate for emissions globally. Lackner said, “CO2 captured today could be counted against emissions that happened last month or will happen next month. This, and the fact that CO2 capture from the air can be introduced without the need of phasing out the existing energy infrastructure, makes this method of CO2 capture very interesting.” Lackner estimates that the eventual cost of clean air to energy consumers could equate to $0.25 per gallon of gasoline.
Lackner concludes that “Today’s urgent need for substantive CO2 emission reductions could be satisfied more cheaply by available sequestration technology than by an immediate transition to nuclear, wind or solar energy. Further development of sequestration would assure plentiful, low-cost energy for the century, giving better alternatives ample time to mature.”
The Earth Institute at Columbia University is among the world’s leading academic centers for the integrated study of Earth, its environment, and society. The Earth Institute builds upon excellence in the core disciplines—earth sciences, biological sciences, engineering sciences, social sciences and health sciences—and stresses cross-disciplinary approaches to complex problems. Through its research, training and global partnerships, it mobilizes science and technology to advance sustainable development, while placing special emphasis on the needs of the world’s poor.