Carbon sequestration?

An article in today's Times considers the possibility of storing excess carbon dioxide under very cold water at the deep sea floor.

Several hundred yards beneath the seabed in waters about 10,000 feet deep, the temperature is typically about 35 degrees and the pressure from the water overhead would cause liquid carbon dioxide pumped into porous sediment to stay denser than water, the researchers said.

The idea of carbon sequestration as a solution to global warming has been pushed increasingly by coal enthusiasts and some Democrats (notably Brian Schweitzer, who has developed quite a following at Daily Kos). The idea is, if I understand it, that we convert coal to a liquid gasoline-like state, and then lock away the excess carbon deep underground. Either that or:

...a new process known as coal gasification. These power plants resemble chemical works more than conventional coal-fired power plants. In them, water and oxygen are mixed with the coal to create carbon monoxide and hydrogen. The hydrogen is used as a fuel source, while the carbon monoxide is converted to a concentrated stream of CO2.

That quote is from Tim Flannery, excerpted by Michael G. Richard at Treehugger.

The Treehugger post deals with some of the environmental dangers of carbon sequestration, which can be severe. Those effects arise from the danger of the carbon escaping, however, so it seems they might be mitigated by this deep-sea storage, if it works.

But Treehugger also excerpts some economic limitations that I don't think are answered:

[Coal gasification plants] are not cheap to run: around one-quarter of the energy they produce is consumed just in keeping them operating.
...
Once the CO2 arrives at its destination it must be compressed into a liquid so it can be injected into the ground--a step that typically consumes 20 per cent of the energy yielded by burning coal in the first place.

In other words, that's nearly half the energy output already used up. How much more would be used if instead of merely pumping the gas overland and injecting it half a mile underground we had to get it way out to sea and then convey it almost two miles to the bottom? I can't see how the economics possibly make sense.

David Roberts at Grist recently summed up a much more sensible approach to climate policy:

The energy future is hazy and complex, to say the least, and it's unlikely that any environmentalist or federal official will be able to "pick the right horse" -- predict the fastest, most efficient way to reduce energy use and produce it more safely.

The best way to move forward would be to institute a carbon charge: a cost on carbon emissions, made revenue neutral by reductions in other taxes (payroll, etc.). The crucial benefit is that this puts uniform pressure on the market. It doesn't pick and choose solutions; it doesn't discriminate. It leaves the fine-grained decisions to market actors.

Elegant and practical. Conservative, even. Unfortunately, both parties seem more interested in playing with energy incentives as a way to reward key constituents (ethanol subsidies = presidentially caucusing Iowa corn farmers, for example; tax breaks for oil exploration = do I really have to spell it out?) than in devising workable policy.