I have no doubt that in time, humans are going to burn every bit of coal, oil and gas we can get out of the ground. Fossil fuels are wealth in its purest form, and it just goes counter to human nature to leave it lying in the ground.
Doing so is going to release a huge amount of carbon that has been trapped under the earth for 300 million years or so, and the form that carbon takes is as carbon dioxide. What is becoming increasingly apparent (and I’m hardly the first to notice!) is that putting all that CO2 into the air is a bad idea — potentially a catastrophically bad idea.
So we need to find a way to keep all that CO2 out of the atmosphere, because we are going to burn the fuel. Conservation is not going to save us. Most of the ideas I’ve seen to sequester CO2 don’t really seem to capture the magnitude of the problem. For example, you can buy carbon offsets that will pay for the planting of trees. Think about that. The carbon we’re trying to stuff somewhere has been out of circulation for 300 million years, and somehow putting it up for the life of a tree is going to make up for that?
However, today I read a paper from MIT that has some promise and realism. The proposal is to combine magnesium silicate with CO2. The reaction products are magnesium carbonate and silicon dioxide, both of which are durable on a geologic scale — they’re rocks. Magnesium silicate is highly abundant, much more so than coal. And the kicker is that the reaction is exothermic — magnesium carbonate is lower-energy than CO2, so the reaction produces more energy from the fossil fuels than burning alone.
What are the downsides? Mostly, a lot of mining. The article says:
The process implies a large mining effort, but the areal extent of the mine is small compared to the
coal mine that produces an equivalent amount of coal. Overburden on serpentinite rock is
generally insignificantly small and the minerals occur in thick layers rather than thin seams.
Nevertheless, the mass of material required is larger by a factor of six than the mass of coal that is
used as fuel.
The products of the reaction are less dense than the source materials, so there is also an increase in volume associated with the reaction. So we can’t just dump the waste back into the hole they came out of, we need to stack them
The article can be read here: http://sequestration.mit.edu/pdf/carbonates.pdf