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http://www.wired.com/news/planet/0,2782,69711,00.html?tw=wn_tophead_4 intringuing, i wondered how economically/energy viable it is to pump 1 tonne of CO2 into the ground. a quick back-of-the-envelope calc using numbers from the article and assuming you have a bore-hole 30cm in diameter, earth is uniform basalt and liquid (no caves), CO2 is liquid (at those depths), adiabatic & steady processes, isothermal compression of gaseous CO2 to liquid, 100% efficient machines, googling for relevant parameters, etc. . . . . .requires about 600 Mega Joules to pump 1,000 kg of CO2 into the bedrock (most of the energy used to liquify the gas, i think thats justifyable). but 1 kg of coal produces 30.9 Mega Joules of energy (wikipedia). assuming 40% efficiency of burning coal and pumping into ground, it appears this method requires about 70kg of coal to pump 1 tonne of CO2 into the ground. finally if i naiviely assume coal is almost completely made out of carbon (i.e. 1kg coal makes ~3kg of CO2) then about a fifth of the energy from coal will go into carbon sequention to make the whole process "carbon neutral". this process is going to be darn expensive! especially since i didn't take into account the "startup" energy needed to reach steady state - thats going to be *huge*. this whole carbon sequention idea postively makes nuclear power look cheap!!! . . . or is that the point?. . . coal is the cheapest form of energy, but if coal was "forced" to be CO2 neutral. . . nuke would rule, easy. everyone knows BNFL employs crafty little buggers to whisper words in government ears, so . . .? anyway its just speculation (must stop playing conspiraracy games!). last paragraph in the article kindof sums this up sequention costs(ish). nav ps: *people* this was a back of the envelope calculation! so dont go quoting it in interviews. chances are many of the approximates wont be wholly true, but i estimate it should be accurate well within an order of magnitude - which probably isn't saying much. does anyone want to have a go at calculating a more accurate figure? or find it?