Biosequestration

The latest version of the Oak Ridge National Laboratory Review examines whether America can simultaneously achieve energy independence and contain global warming.  It is an interesting read, and I want to examine their research on biosequestration. 

Human progress/activities add 10 billion tons of carbon dioxide annually to the atmosphere.  Projections are it will increase to 20 billion tons by 2050.  Researchers are studying how to capture CO2 and either store it underground or deep underneath the sea.  There are several technical and political obstacles for either of these techniques, but the planet has been naturally supporting biosequestration since the beginning of life.  Can we somehow coax the Earth's ecosystem to sequester more carbon dioxide?

The researchers at Oak Ridge National Laboratory (ORNL) estimate that natural processes have a net sequestration of 2 billion tons of carbon dioxide a year.  We remember photosynthesis from our first courses in science, where green plants convert CO2 into oxygen and sugar.  This production of sugar increases biomass, which can serve as a temporary carbon sink.  For example, a forest is an effective carbon sink as long as it is growing.  The carbon is returned to the atmosphere if the timber is either burned or rots.

Researchers are discovering better ways of keeping that carbon from going back into the atmosphere.  Low-till or no-till agriculture avoids turning the soil over which releases the CO2 that has been absorbed from the atmosphere and transferred into the soil by the plant's roots.  More carbon is currently resident in the soil than all vegetation above ground.

New way to farm boosts climate, too, explains that no-till farming was originally discovered by accident.  A cover crop called hairy vetch had been planted on a field.  A fraction of the field was not harvested, but the cover crop was serendipitously crushed by farming equipment.  When the field was later planted, corn plants grew through the mashed vetch which acted as a mulch for the crop.  After several decades, the soil has absorbed its limit of organic matter, and its ability to sink additional carbon is much degraded.

Researchers at ONRL believe biosequestration can be increased to 5 billion tons (up from two) a year through improved land management and better farming/forestry techniques.  Perhaps ten billion tons, but it would be a stretch of resources. 

Mmm.  Five billion tons of CO2 sequestration.  That is 50% of our current production of 10 billion tons of carbon dioxide.  Seems like much lower-hanging fruit than geo-sequestration or ocean sequestration doesn't it?  Also, we need to keep emissions down to a manageable level instead of 20 billion tons.