Manure Converted to a Variety of Products
July 18, 2001
If you thought cow patties were just something to avoid stepping in, consider this: In the future they could help make plastics, antifreeze, cosmetics, and even deodorants.

Funded by a grant from the Department of Energy, engineers and animal scientists at Washington State University and Pacific Northwest National Laboratory in Richland, Washington, are exploring ways of extracting valuable chemicals from manure. The waste could also provide undigested and purified proteins for making fresh feed for cattle.

"Look at what's in manure," said Don Stevens, a project manager at the Richland lab. "There's a lot of carbohydrates and proteins…of course, the product is real wet."

A single cow produces about 100 pounds of wet manure a day, of which about 20 pounds is dry waste, according to Joe Harrison, an animal scientist at Washington State. A cow's diet includes about 18 percent protein and 30 percent carbohydrates, and about a third to half of what a cow eats comes back out.

The researchers are looking at ways of extracting proteins and amino acids from manure for processing new animal feed. Harrison said such recycled feed would be fed only to non-dairy cows to safeguard against any possible contamination of milk products.

Chemical Source?

Stevens and his team are also exploring the use of manure's carbohydrates to make chemicals.

Glycols, diols, and other chemicals used in many plastic products and cosmetics are usually processed from petroleum. Rather than drawing a resource from underground, the researchers hope to scoop up another, cheaper material from farm stalls. They say the abundance of carbohydrates in animal manure could provide the building blocks for chemical production.

The process that would be used to process the patties is not new. The Richland lab has already developed ways of extracting chemical building blocks from corn mash left over from ethanol production and grains remaining from wheat mills. Manure processing would employ similar methods, although it would be a messier product.

"Manure is a dirtier stock," said Stevens. "It not only has carbohydrates, but also rocks and stones and sticks and who knows what."

Plentiful Resource

Why bother tinkering with such a stinky resource? Because it's plentiful.

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."

Copyright 2001

© 1996-2008 National Geographic Society. All rights reserved.