There is one interesting way to capture carbon without having to spend hundreds of millions of $. Use the CO2 to replenish and rebuild soils while at the same time sequestering them under the ground!
Listen to this: "USGS, California and UC Davis begin large-scale Delta “carbon farm” Project will study best ways to capture atmospheric CO2, reverse island subsidence - The U.S. Geological Survey (USGS), the California Department of Water Resources (DWR) and the University of California, Davis plan to make it happen. DWR has awarded USGS and UC Davis a three-year, $12.3 million research grant to take the concept of carbon-capture farming to full-scale in a scientifically and environmentally sound way. Long-standing farming practices in the Delta expose fragile peat soils to wind, rain and cultivation, emit carbon dioxide (CO2) and cause land subsidence. To capture or contain the carbon, farmers would “grow” wetlands. In doing so, they would begin to rebuild the Delta’s unique peat soils, take CO2 out of the atmosphere, ease pressure on the Delta’s aging levees and infuse the region with new economic potential. Carbon-capture farming works as CO2 is taken out of the air by plants such as tules and cattails. As the plants die and decompose, they create new peat soil, building the land surface over time." (Source: http://powerplantccs.com/blog/2010/03/large-scale-carbon-capture-farming-to-rebuild-soils.html
Don't you think this is an effective way of carbon sequestration? But my worry is that this might take a long time to suck out the humungous amounts of extra CO2 we have gleefully pumped into the atmosphere. We probably will need more synthetic methods to suck it out faster, what do you think?