It is hard to think of animal manure as a valuable commodity. But with 160 million tons of it produced annually in the United States, and most of it rich in carbohydrates and proteins, researchers at the Department of Energy's Pacific Northwest National Laboratory and Washington State University see potential in converting substantial portions of it to commodity chemicals and other high-value products.
PNNL and WSU are beginning a two-year study to determine the best processes to generate higher-value products from manure. The study is being funded by an $800,000 grant through DOE's Office of Energy Efficiency and Renewable Energy and is focused on developing new processes to use animal manure as feedstock for commodity chemical production.
The team will use the carbohydrate- and protein-based chemical building blocks from manure to produce a range of products. The carbohydrate material, composed of five- and six-carbon sugars, will be converted to commodity chemicals, such as glycols or diols, commonly used to manufacture antifreeze or certain plastics. The protein components will be converted to animal feed and other higher-value products.
PNNL has developed innovative catalytic approaches for converting other low-value biobased materials to chemicals, such as the wastes and by-products resulting from processing corn, wheat, potatoes and dairy products. Researchers at PNNL separate the carbohydrates and oils from low-value feedstocks. The carbohydrate fraction then is catalytically converted to higher-value products. This approach will be applied to manure, described as a messier resource by Don Stevens, project manager for the PNNL work.
"While some biomass feedstocks, such as wheat wastes, are made up mostly of clean carbohydrates, manure is messier with only about half of it consisting of carbohydrates. Additionally, manure contains a much higher protein percentage and a greater mix of minerals," said Stevens. "The production of chemicals is therefore more complex and the processes must include more extensive separations of these components to be useful for chemical production."
PNNL is teaming with WSU researchers because of their extensive experience in separations chemistry and in recovery of high-value protein products. WSU is a land grant university and operates a dairy and feedlot in Pullman, Wash.
The payoff could be huge—environmentally and economically. "Animal waste is increasingly difficult to dispose of. With fewer, but larger, animal operations across the United States, the waste is more geographically concentrated, resulting in more environmental problems," Stevens said.
"By successfully converting the wastes into chemicals, we can greatly reduce the need for open-field disposal of manure, which will reduce odor problems, methane emission to the atmosphere and run-off of contaminants into streams and lakes."
Another payoff is reducing the number of petroleum-based products on the market. Currently, almost all the medium-volume commodity chemicals, such as those used to make antifreeze, carpet fibers and soda pop bottles, are petroleum-derived. Stevens said it's conceivable that in a few years biobased products could directly replace some chemicals currently made from petroleum resources.
They also could be cheaper to produce. Stevens said the kinds of chemicals the team is focusing on are potentially more efficient to produce from biomass feedstocks than petroleum, and that the total energy required for their production is roughly half when compared to the same chemical from petroleum.
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Pacific Northwest National Laboratory is a DOE research facility and delivers breakthrough science and technology in the areas of environment, energy, health, fundamental science and national security. Battelle, based in Columbus, Ohio, has operated the laboratory for DOE since 1965.