My latest idea is the mobile coal-burning electrical generator. It's used in older oilfields, where CO2 is either desired to assist in oil production, or where it's merely acceptable to dispose of the CO2 exhaust in played-out oil or gas sands far below the surface. The requirements are only that a rail line be nearby and transmission towers for the power generated be nearby. Short temporary pipelines and power lines are acceptable. When each subsurface formation is optimally full of CO2, the mobile plant is moved to its next location.
This is for areas where CO2 pipelines are not available. See "green pipelines."
Coal cars are delivered to the generator during its period of sequestration / generation at each location. Some sulfur gases may also be sequestered underground.
The plants are not as efficient as other coal burning power plants because some power is used to deposit the CO2 into the deep formations.
The ridiculous illustration I cobbled together merely shows the equipment needed: a power plant, a generator, a transformer, and a pump for the burned exhaust gases. Ash will also need disposal. There will be empty rail cars after they deliver coal. It is possible ash could also be pumped into the same formations and could possibly neutralize the low pH of the sulfur, if any. As always, groundwater must be protected; these techniques already exists.
Cooling water for the turbine is the biggest problem. To generate electricity with a turbine efficiently, cooling is mandatory. Brine water present in many oil-bearing formations could possibly be used. Engines need a heat difference.
My back-of-the-envelope calculations (done mentally- can you scribble mentally on the back of an imaginary envelope?) tell me this would never amount to over a few hundred megawatts nationally. I can't say with certainty however that this a completely worthless idea. It might contain the germ of something worthwhile.
UPDATE 4-14-09 Scientific American has several articles on one page dealing with carbon sequestration.