Turfgrasses, Carbon Dioxide and Global Warming (Part 1 of 2)
Thomas J. Samples, Ph.D. - Plant Sciences Department, The University of Tennessee
A question often asked of students studying turfgrass science and management is "Which of the following - light, temperature, water (H2O), atmospheric carbon dioxide (CO2) or nutrition - is most important for turfgrass survival?" One correct answer is, "All are equally important."
More difficult and complex questions are "What is the capacity of turfgrasses to remove and store, or sequester, carbon (C) from the atmosphere?" and "Does this help prevent global warming?" These questions force students to recall what they've learned about photosynthesis 6CO2 + 6 H2O + light energy _C6H12O6 + 6O2, the ability of turfgrasses to capture and store C, the greenhouse effect, and the oceans' role in C sequestration.
Approximately one-half of the photosynthesis on Earth occurs on land, and the remainder in water (f). Both ocean and land plants share the same basic requirements for photosynthesis and growth. These requirements include light, an appropriate temperature, H2O, CO2 and nutrients.
Although nitrogen (N2) and O2 account for 78 and 21 percent of the dry atmosphere, respectively, these gases contribute very little to the greenhouse effect. Greenhouse gases in the atmosphere, including CO2, hydrofluorocarbons (HFCs), methane (CH4), nitrous oxide (N2O), ozone (O3), perfluorocarbons (PFCs), sulfur hexafluoride (SF6) and water vapor, act as a partial blanket for long-wave radiation coming from the earth's surface. They let energy from the sun in, but don't let all of the heat energy out. This blanketing results in a natural greenhouse effect, warming the earth's surface.
Water vapor and CO2 are two very important greenhouse gases. Human activities have had only a small, direct influence on the amount of water vapor in the atmosphere. During the past 20 years, fossil fuel burning has contributed about three-quarters of the atmospheric CO2 emissions resulting from human activities (g). For several thousands of years before the Industrial Era, which began about 1750, the atmospheric CO2 concentration was 280-10 parts per million by volume (ppmv) (g). Since then, it has risen, reaching 379 ppmv in 2005 (p).
Carbon dioxide is soluble in water. Presently, the oceans take up about two billion metric tons of C annually (k). Most of the CO2 taken up by the oceans combines with water to form carbonic acid (H2CO3). Some of the CO2 is captured in photosynthesis by plants, such as algae or phytoplankton, living in the sea water.
Possible strategies to global CO2 issues are being proposed, discussed and researched (a, b, j). One method being considered to maintain or reduce the level of CO2 in the atmosphere is to remove and inject it into natural reservoirs not in contact with the atmosphere. These include deep geological formations or the oceans. Production from some oil and natural gas reservoirs can be enhanced by pumping CO2 gas into the reservoir to push out the product. The U.S. leads the world in enhanced oil recovery technology (c). About 32 million tons of CO2 are used for this purpose each year (c). Liquid CO2 could be pumped to an ocean depth of 3,200 ft. or more, where the gas is denser than sea water (d). Estimates of the amount of CO2 (Gigatons of C, where 1 Gigaton = 1 billion metric tons of C equivalent) that could be stored in reservoirs in order of magnitude are: oceans, 1000s; deep saline formations, 100s to 1000s; depleted oil and gas reserves, 100s; coal seams, 10s to 100s; and terrestrial, 10s (d).
References:
a. Anonymous. 2008. Carbon services- We’re involved. Schlumberger. http://www.slb.com
b. Anonymous. 2007. Cold storage solution for global warming? Carbon dioxide could be frozen in underground reservoirs. ScienceNews. February. http://www.sciencedaily.com
c. Anonymous. 2008. Geologic sequestration research. Fossil energy. U. S. Dept. of Energy. http://www.fe.doe.gov
d. Anonymous. 2003. Watching brief: Ocean carbon sequestration. Intergovernmental Oceanic Commission of UNESCO. Scientific Committee on Ocean Research. http://ioc.unesco.org
e. Bremer, D. 2007. Carbon sequestration in turfgrass: An eco-friendly benefit of your lawn. TurfNews. Kansas Turfgrass Foundation Newsletter, October.
f. Gutro, R. 2003. NASA study solves ocean plant mystery. Goddard Space Flight Center. August. http://www.nasa.gov
g. Intergovernmental Panel on Climate Change, 2007: Climate Change 2007: The physical science basis. Contribution of Working Group I to the fourth assessment report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (Eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
h. Kent, S., G. Morris, K. McConnaughay and S. Morris. 2007. Carbon sequestration in urban turf soils. ASA, CSSA and SSA International Annual Meetings. 98-8.
I. Kiser, K. 2008. For carbon offset, look no further than your own backyard. Outdoor Power Equipment Institute. http://www.opei.org
j. Luoma, J. 2008. Greenhouse graveyard: New progress for big global warming fix. Popular Mechanics. July. http://www.popularmechanics.com
k. Preuss, P. 2001. Climate change scenarios compel studies of ocean carbon storage. Science Beat. Berkeley Lab. http://www.lbl.gov
l. Qian, Y. and R. Follett. 2008. Soil organic carbon input from urban turfgrasses. 2008 Joint Meeting of the Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM. 68-2.
m. Qian, Y. and R. F. Follett. 2002. Assessing soil carbon sequestration in turfgrass systems using long-term soil testing data. American Society of Agronomy. Agron. J.: 94:930-935.
n. Revkin, A.C. 2007. Carbon neutral is hip, but is it green? New York Times. April 29.
o. Sahu, R. 2008. Research report: Technical assessment of the carbon sequestration potential of managed turfgrass in the United States. Outdoor Power Equipment Institute, Inc. http://www.opei.org
p. Zalasiewicz, J., M. Williams, A. Smith, T.L. Barry, A.L. Coe, P.R. Bown, P. Brenchley, D. Cantrill, A. Gale, P. Gibbard, F.J. Gregory, M.W. Hounslow, A.C. Kerr, P. Pearson, R. Knox, J. Powell, C. Waters, J. Marshall, M. Oates, P. Rawson, and P. Stone. 2008. Are we now living in the Anthropocene? The Geological Society of America. GSA Today. 18(2): pp. 4-8. http://www.gsajournals.org