Carbon sequestration is one of those ideas that sounds great when you first hear about it. The idea is simple: carbon dioxide is captured (either at the point of production or extracted from the air) and locked down, either in biomass (like trees), in chemical combinations, or stored underground in vast, nearly-airtight chambers. It has its drawbacks, though. Some proponents explicitly use it as a rationale for continued -- even increased -- CO2 production, arguing that if the results are still a net reduction in atmospheric carbon dioxide, we shouldn't worry. Unfortunately, just how long the CO2 would remain trapped is an open question -- dead or burned biomass or leaks from underground storage could return the sequestered carbon back into the atmosphere, once again increasing CO2 levels.
A Penn State research group might have developed a method of locking away CO2 without running the risk of its escape. They've figured out how to accelerate a natural process where serpentine -- an abundant mineral -- combines chemically with CO2.
When serpentine dissolves in sulfuric acid, the silicon in the mineral becomes silicon dioxide, or sand, and falls to the bottom, while the magnesium becomes magnesium sulfate. Treating some of this magnesium sulfate with sodium hydroxide also creates some magnesium hydroxide. The researchers were able to convert large amounts of the serpentines magnesium to these chemicals providing large surface areas for reactions to occur in solution at room temperature.
Carbon dioxide passed through the solution of magnesium sulfate and magnesium hydroxide converts both to magnesium carbonate or magnesite, which becomes a solid and falls to the bottom. This solid can be used to manufacture construction blocks and there is also a small market for hydrated magnesium carbonate in the cosmetics industry. The silicon dioxide can be used to remove sulfur dioxide from the flue gases, which can subsequently be converted to sulfuric acid to use in the first part of the process.
Sequestration alone is not a solution to increased CO2 concentrations in the atmosphere. Coupled with aggressive moves away from greenhouse gas-emitting processes, however, sequestration might make a difference in keeping the planet away from tipping into disaster. Better, then, that the method used to sequester carbon dioxide not be something that could bite back hard a few years down the road.
On originally hearing about sequestration being promoted by the head (or is it the ex-head) of Shell I thought to myself "ah-ha" they are promoting this unproven and hugely expensive technology so they can keep producing fossil fuels and get everyone to pay for it.
However upon reflection:
I've decided I'm for sequestration
IF, and only if the industries involved pay for it. This will disincentivise fossil fuel use and promote the use of clean renewables.
The challenge is making this a political and economic reality.
The easy way to store carbon for 100-200 years cheaply is store it in used baby diapers dumped in a sealed water resistant landfill.