Taking Inventory
of Carbon Emissions


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The U.S. Environmental Protection Agency announced a proposed set of regulations in June that would work to reduce annual greenhouse gas emissions from existing power plants by 30 percent by 2030. That’s part of a larger program of fuel efficiency and other measures designed to bring economy-wide emission levels down 17 percent from a 2005 baseline by 2020.

Power plant emissions of greenhouse gases—mostly carbon dioxide that is created by the burning of fossil fuels—are the focus of these new regulations for good reason. Thermal generating stations that burn coal, natural gas, or fuel oil vented more than 2,000 million metric tons of carbon dioxide into the atmosphere in 2012. That’s more than 30 percent of the 6,525 million metric tons that were emitted by the entire economy, according to EPA figures published earlier this year. (The net emissions are almost 1,000 million metric tons less than this because of carbon sinks, which have grown through forestry activities and land use changes.)

The second largest source of emissions is burning petroleum—gasoline, diesel, jet fuel, and so on—to power transportation. This sector is also subject to regulations that are designed to improve efficiency; by model year 2016, the corporate average fuel economy for vehicles sold in the U.S. will increase to 39 miles per gallon for cars and 30 mpg for light trucks. Most automakers who sell cars in the American market have agreed to make additional improvements, to 54.5 miles per gallon for cars and light-duty trucks by model year 2025. This is better than double what the CAFE standard was as recently as 2008.

These measures should continue trends that have pushed the U.S. off the track of ever-increasing greenhouse gas emissions. Since 2005, the nation has reduced emissions by 728 million metric tons, though those reductions have not been distributed evenly. Coal-fired power plants, gasoline-powered light trucks, and industrial combustion of oil and coal have seen major cuts; gasoline use in passenger cars, and natural gas combustion for industry and electricity generation have seen increased emissions.

Those last increases are likely net reductions as gas has supplanted more carbon-intensive coal and oil in many cases. Even so, the total greenhouse gas emissions from fossil fuel combustion account for more than 5,000 million metric tons, and while the scheduled cuts are more than just a shave, they won’t come close to what will be needed to reduce the pace of increase of carbon dioxide in the atmosphere. To do that will require much more effort in many more countries over a longer period of time.

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August 2014

by Jeffrey Winters