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ORNL researchers focus on the CO2 big picture

23.04.2004

Spring’s lush green lawns and hot pink shoes contribute at least in a small way to the world’s total carbon picture, say researchers at the Department of Energy’s Oak Ridge National Laboratory.

Indeed, the latest fashions on Fifth Avenue and fertilizers that help homeowners achieve that "barefoot" lawn have their associated carbon dioxide costs, and ORNL’s Gregg Marland and Tristram West keep up with them. Their task is to track the total carbon produced worldwide and estimate how much is taken up and cycled through trees, plants, soil and goods produced from these resources. The overall goal is to determine the net impact that people and their activities have on our planet.

"Energy use is embodied in everything that we use and buy," Marland said. "And just because you may not be burning the fossil fuel yourself, don’t kid yourself into thinking that someone isn’t burning it on your behalf."

Each person’s annual share of carbon dioxide emissions in the United States is 5.4 metric tons, or nearly 12,000 pounds. One-third of those emissions is from power generation, another third is from internal combustion-powered vehicles, and the remaining third is from other sources, including fossil fuels used in factories, office buildings, homes and for daily activities like lawn mowing.

Carbon dioxide, considered a greenhouse gas, is increasing in the atmosphere each year and is thought to be a major factor in climate change.

"From producing the latest in shoes to building cars and home improvement products, it all requires electricity and power plants to generate that electricity," Marland said. "So staying in fashion can actually be costly to the environment because people are constantly replacing perfectly good clothing, shoes, furniture and home accessories with the latest styles."

A recent analysis by West shows that nearly 22,000 manufacturers in the textile and apparel industry emitted about 12 million tons of CO2 in 1998. And West noted that this number doesn’t include the energy and emissions associated with the nearly 19 billion square meters of garments imported to the U.S. each year.

Looking at lawns, West noted that there are a number of associated costs to the environment, ranging from mining lime and manufacturing fertilizer to the greenhouse gases emitted from fertilized lawns. And grass that grows faster needs to be mowed more frequently, which further increases CO2 emissions.

Putting this into further perspective, fertilizing one acre of lawn at the recommended rate of 137 pounds per acre results in 405 pounds of carbon dioxide-equivalent emissions from the production, transportation and application of the fertilizer. This includes CO2 and N2O emissions, which are both reported in units of CO2.

These emissions are equivalent to the amount of CO2 released from an average family sedan driven about 440 miles. But residential use of fertilizer accounts for just a fraction of the more than 11 million tons of nitrogen fertilizer used in 2002 in the U.S. The majority of fertilizer is used in agriculture, and West noted that their research focuses primarily on management of agricultural lands.

"A change in agricultural practice can increase carbon sequestration in agricultural soils," West said. "To know the net effect on greenhouse gas emissions to the atmosphere, however, we consider associated changes in CO2 emissions resulting from the consumption of fossil fuels, emissions of other greenhouse gases and effects on land productivity and crop yield."

Marland, West and Bernhard Schlamadinger of the Institute of Energy Research in Austria study these impacts using a model they developed called the Graz/Oak Ridge Carbon Accounting Model. It allows them to evaluate the net flux of greenhouse gases to the atmosphere for various forest management and agricultural alternatives.

ORNL is managed by UT-Battelle for the Department of Energy.