Earth Equity News

Heavier Crudes, Heavier Footprints. By Janet Raloff, Science News, 12/3/10. “Relying on heavy oils and tar sands as the feedstock for liquid fuels will exaggerate the greenhouse-gas emissions associated with fossil-fuel use, a new study finds. Light crudes are the easiest to work with. But as their biggest and most accessible reservoirs have been tapped -- and often tapped out -- the oil industry has increasingly been turning to what has been termed ‘unconventional’ stocks. These are viscous, if not tarry, forms of petroleum. And as the upper graph below shows, the average ‘gravity’ -- viscosity of crude -- has fallen into the heavy range (below an average of about 31 degrees on the American Petroleum Institute scale) beginning in 2000… it takes extra work to convert viscous gunk into the gasoline, diesel and other high-value fuels that power engines the world over. And the extra fuel that powers those upgrades releases bonus greenhouse-gas emissions, thereby upping the carbon footprint of each gallon of refined product created.”