The study showed that used grounds contain about 15 percent oil by weight, depending on the type of coffee. That's not too far off the proportions in soybean, rapeseed, and palm oils, which are also used as sources for biodiesel. And coffee oil is more stable than these other sources because of its high antioxidant content, found the study, which appeared in December in the American Chemical Society's Journal of Agricultural and Food Chemistry. Around the world, growers produce more than 16 billion pounds of coffee each year, according to the U.S. Department of Agriculture. The scientists estimate that spent grounds could add 340 million gallons of biodiesel to the global fuel supply. Mohapatra envisions a streamlined coffee recycling system, in which the same trucks that deliver beans to Starbucks could pick up the brewed waste and head to a biodiesel plant. The plant would be close by, to save on transportation costs and emissions. Coffee grounds appear to produce high-quality oil, granted Robert McCormick, an engineer at The National Renewable Energy Laboratory in Golden, Colorado. But, he said, coffee probably won't be a practical solution to the world's energy needs. For one thing, the country's main sources of biodiesel -- cooking oil and animal fat -- are 100 percent oil, compared to coffee's 15 percent. And even when a cafe brews a large amount of coffee, relatively few grounds are left behind. It takes 50 gallons of spent grounds to produce just 1 gallon of oil, Mohapatra said. Still, McCormick commends the researchers for thinking outside the box about the world's energy issues. "Anything that takes a waste product and makes a fuel out of it is really a positive," he said. "This is pretty cool." Related Links: |
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