Our Sustainable Earth

As scientists assess mounting evidence of a new geologic epoch where human activities will largely control the evolution of our Earth’s environment, they have coined this epoch, “The Anthropocene.” Don’t look now, but you’re living in it.   What we don’t know is whether our influence on climate during the Anthropocene will be a short-term, relatively minor change from the current climate, or an extreme deviation that lasts for thousands of years.  (Related, from National Geographic Channel: How the Earth Changed History, “New Earth Epoch Has Begun, Scientists Say”)

The conundrum we face is alarming.  Some take heart in the latest estimates from The Energy Information Administration of the Department of Energy, showing that the growth in U.S. annual carbon dioxide emissions has slowedgrowth in U.S. annual carbon dioxide emissions has slowedgrowth in U.S. annual carbon dioxide emissions has slowed.  But slower growth is still growth, and the longer we increase carbon dioxide emissions, the longer we allow equilibrium effects to amplify warming.

I’m speaking of dire consequences.  What do I mean, and where is the evidence?  Often indicators (air temperature near earth’s surface, sea level, humidity, sea-surface temperature, temperature over oceans, ocean heat content, temperature over land, area of snow cover, glacier mass, extent of sea ice), all change in the direction of global warming (the first seven increase, the last three decrease, respectively).  Further, the last three decades all show significant warming.  The decade of the 1980’s was the warmest global temperature decade on record at that time.  The decade of the 1990’s was even warmer, with every year warmer than the 1980’s average.  And the decade of 2000-2009 was still warmer, with every year warmer than the 1990’s average.  Evidence of global warming is incontrovertible.

What to do, even as other countries grow their economies and, therefore, their emissions?   There are technological opportunities that can deeply reduce carbon dioxide emissions, without a price on carbon or regulation.  They are premised on being able to survive in the market place without subsides or energy price increases.  They do require investment, and collaboration between research universities, State and Federal Governments, and the private energy sector.

An example is coal-fired power plants that in the U.S. currently generate 2,100 million metric tons of carbon dioxide each year.  That amounts to roughly a third of the total annual carbon dioxide “footprint” of the U.S.  Yet, the current approach to capture the carbon dioxide and sequester it (CCS) in deep-lying aquifers is not economically feasible without either large subsidies or a very high price on carbon, for current CCS methods require approximately 1/3rd of a power plant’s energy for carbon dioxide capture and pressurization.  Neither merchant nor regulated utilities can survive with this additional cost.

The University of Texas at Austin, in conjunction with two utilities, has developed a combination of two technologies, and introduced a third, that together could reduce the cost of CCS to a point that CCS would survive in a competitive market environment without subsidies or a price on carbon.

Specifically, the production of energy from geothermal aquifers and the sequestration of carbon dioxide and other greenhouse gases in deep, saline aquifers have evolved as separate, independent technologies. UT Austin has proposed a new idea that combines these two technologies and adds another: dissolution of carbon dioxide into extracted brine, which is then re-injected. Additional elements are the production of energy from the extracted brine to help offset the cost of capture, pressurization, and injection and the subsequent injection of brine containing carbon dioxide back into the aquifer.  Realistic simulations indicate that the combined value of the methane and heat energy from the produced saline water is of the same order as the cost of separating, pressurizing and injecting the carbon dioxide.  And geologic studies have shown that there is a huge amount of methane dissolved in aquifers near and along the Texas, Mississippi, and Louisiana coasts.

Simulations show that 29.4 million tons of carbon dioxide can be stored in this aquifer, with about half of the original methane produced, amounting to 98 billion SCF.  Adding in the value of the saline liquid heat, the total energy generated would be worth more than the current cost of capturing and pressurizing carbon dioxide from associated coal-fired power plants.

This concept deeply reduces carbon dioxide emissions from coal-fired power plants without increasing the cost of electricity.  It is both economical, and meets the need for thermal stabilization of our earth.  It is also global in that methane saturated geopressured geothermal aquifers are common in most parts of our world.  Other concepts need development and application if we are to save life as we know it on our planet.  There is no more important moral imperative than global thermal sustainability.