CO2 Injection - Good, Wastewater Injection - Bad

In the recently published April 2014 National Geographic, the main article was “Can Coal Ever Be Clean?”  The article described use and abuse of coal in the U.S. and elsewhere.  One of the “clean” discussions was sequestering carbon dioxide underground in “porous rock formations.”  Believe it or not, the DOE has spent more than $6.5 billion over the last three decades researching and testing the technology.  That is another story for another day.  As an example of CO2 sequestration, they sited Statoil, a Norwegian oil and gas company, who produces gas from the Sleipner gas field in the North Sea.  According to the National Geographic, for the past 17 years the company has been injecting about a million tons of CO2 per year into a brine-saturated sandstone layer half a mile below the seabed.  That formation has so much room that all of that CO2 has not increased its internal pressure, and there has been no sign of quakes or leaks.

Switching to a Bloomberg article today, they reported that several U.S. states are banding together to combat the mounting risks of earthquakes tied to the disposal of wastewater from hydraulic fracturing for natural gas.

So what does CO2 sequestration from coal have to do with disposal of wastewater from hydraulic fracturing for natural gas?  Both rely on drilling holes into the ground with the same equipment.  Both rely on injecting a substance under pressure – one water and the other gas.  Drilling for natural gas relies on drilling a horizontal hole through impervious, impermeable shale and fracturing it to create porosity and permeability.  Sequestration of CO2 from the combustion of coal relies on horizontal porous and permeable sandstone formations for storage.  So, both rely on vertical and horizontal pathways to move either a liquid or a gas.

So, how is it that in the coal sequestration case, it is good to pipe CO2 under pressure back into the porous rock formations and it is bad to pipe water under pressure back into the porous rock formations?  Both require the testing of internal pressure as a guide for how much can be pumped back into the earth.  Clearly water is denser than CO2 and less compressible than gas.  But the big difference between the two is that CO2 gas expands upon release and will skyrocket to the surface if there is an earthquake that penetrates the porous sandstone formation.  The concentration of the escaping CO2 will likely kill all kinds of life on its release.

The National Geographic interviewed geophysicists Mark Zoback and Steven Gorelick of Stanford University.  Both argued that at sites where the rock is brittle and faulted – most sites in their view – the injection of carbon dioxide might trigger small earthquakes that, even if otherwise harmless, might crack the overlying shale and allow CO2 to leak.  Zoback and Gorelick consider carbon storage “an extremely expensive and risky strategy.”

Bloomberg reported (in the same article as above mentioned) that according to the U.S. Geological Survey, pumping fracking wastewater underground has been linked to six-fold jump in earthquake in the central U.S. from 2000 to 2011.

Source: EPA - Overview of Greenhouse Gases

The Bloomberg article reported that regulators from Kansas, Texas, Oklahoma and Ohio met for the first time this month to exchange information on the man-made earthquakes and help stated toughen their standards.  That is all fine as long as the same standards are applied to CO2 sequestration.  With natural gas representing 20% of the fuel source for electric power and coal representing 46% of the fuel source for electric power (data from the U.S. Energy Information Administration), we need to be careful not to put the electric power utilities into a corner.   The chart to the left depicts the US Carbon Emissions, by source.

While I am an advocate of solar and other renewables, uranium, coal, and oil are the most energy dense materials in the world and therefore the most efficient.  See the below first chart - uranium is literally off the chart.  

That would be why they were developed first.  We need them until something better can be developed.  Coal usage is on the decrease for reasons mentioned above, in addition to more efficient homes, more efficient appliances, the introduction of LED light bulbs (FYI, lighting represents 66% of the average U.S. household consumption of electricity), etc.  Along with that decrease in coal use, CO2 emissions are down significantly since 2004.  The chart shows a decrease of over 10% in 7 years.

Source: EPA - Overview of Greenhouse Gases

The U.S. has not had a coherent energy policy in years.  Let's set one up and then decide how to proceed.