Explosive Science: a Sexy New Answer to Climate Change

      
            What can rock deformation do for you?  Maybe turn your car exhaust into limestone!

            Climate change is one of the most talked about issues of the last two and a half decades.  Though its existence is now generally accepted, debates about its causes, extent and what’s to be done continue to rage; however, it has become clear that one major cause of climate change is increased levels of carbon dioxide gas in the atmosphere.  Diverse solutions have been proposed, from massive reforestation efforts to iron-seeding the oceans to stimulate algal blooms, all of which have encountered resistance from various environmental and/or industrial groups.

Industrial processes release carbon dioxide and other byproducts into the atmosphere.

One of the proposed technologies that has emerged at the front of the pack is geological carbon sequestration, or the practice of pumping carbon dioxide into the ground to remove it from the atmosphere.  This technology generally assumes two forms, reservoir sequestration and mineralization.

Reservoir sequestration involves storing carbon dioxide as a gas trapped in non-economic coal seams or dissolved in non-potable aquifers.  This method is popular because it is essentially already in use by the hydrocarbon drilling industry in the form of enhanced oil recovery.  Several notable drawbacks include contamination of potable aquifers, acidification of groundwater and concomitant changes in the mechanical behavior of reservoir rocks and catastrophic degassing and asphyxiation.

Mineralization takes advantage of natural reactions of minerals from deep within the earth with carbon dioxide in the atmosphere to form stable carbonate rocks.  The main benefit of this method is that it is safe.  The carbon dioxide gets stored as stable carbonate rocks, and is therefore relatively static.  The drawbacks of this method are mostly cost related.

Carbonate minerals precipitated in old mantle rock.

The reaction of deep minerals and carbon dioxide happens spontaneously, but slowly on human time scales.  To speed up the reaction, the materials must be ground to increase the amount of material exposed to carbon dioxide and heated to speed up the reaction.  Mining, transporting, and heat treating the rocks then manufacturing filters to put on smokestacks world-wide would be too energy intensive to make a real impact on carbon emissions.

However, there may be another way.

The reaction of carbon dioxide with mafic minerals actually releases energy in the form of heat, so once initiated the reaction can be self-sustaining.  The reaction also has a positive change in volume.  A runaway positive volume change reaction in a confined space is usually referred to by another name: a bomb.  If we can harness this power of this natural bomb to fracture the rocks, creating pathways for fluid flow and exposing fresh reactive material, we could maintain a self-heating, self-pulverizing in-situ carbon dump.  BAM!

           In our lab, we have been designing an apparatus to run carbon dioxide-rich fluids through reactive materials during active deformation and monitor the changes in mechanical and transport property behavior.  We plan to test different pressure and temperature regimes to see if we can constrain under which conditions this reaction driven cracking might take place.  This is still a new area of research, so there is much to learn.  The myriad possibilities make it truly exciting science!

First image from the Library of Congress.
Second image from http://cain.ice.ucdavis.edu/repository/SerpWebSoilPics.htm