In the United States alone, about 160 million tons of animal waste is deposited annually. Farmers usually spread the manure for drying or funnel it into lagoons, and then extract and dry it for spraying on farmland as fertilizer.
But dried manure isn't ideal fertilizer and the product is worth only about a penny a pound. Stevens estimated that if the leavings of cows, chickens, and pigs is used to manufacture chemicals, it could be valued at up to 40 cents a pound.
Most important, the process could provide one way to reduce the harmful leaching of phosphates and sulfates from wet manure into waterways and lakes. Stevens said federal protection laws for salmon have forced farmers to stop the common practice of draining liquid manure into streams and rivers.
Stevens hopes that to avoid polluting freshwater sources, manure could be transported instead to chemical processing plants and converted into more useful materials. There are no estimates yet on the cost of processing the manure for chemicals, but Stevens said it should be less costly and twice as energy efficient as using petroleum.
Although the researchers are experimenting initially with cow manure, Harrison said they won't discriminate when it comes to waste because hog and poultry manure might prove equally valuable.
"Swine and poultry waste, I'd rather not touch," he said. "I'd rather handle cow manure. But that's just a personal thing."
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