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United States Department of Agriculture

Agricultural Research Service

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There’s Magic in Manure!

In fairy tales, frogs can become princes. Magicians can yank rabbits from a hat. And now, scientists with the Agricultural Research Service have pulled off one of the neatest tricks yet.

They’ve taken something that most people find pretty gross—animal manure—and turned it into something special!

It may sound bizarre, but it’s true. The researchers have created a powerful water cleaner—a pollutant-picker-upper, to be exact—from the stinky slop that’s produced on chicken farms. And this one-of-a-kind material could work wonders for our environment!

ARS scientists Isabel Lima and Wayne Marshall at the Southern Regional Research Center in New Orleans, Louisiana know that animal waste is a serious problem in the world. We need farm animals for all the meat, cheese, and milk they provide us.

But animals also produce a lot of smelly waste—even though they can’t help it. After all, humans do, too!

Have you ever seen cow patties the size of Frisbees? Or the little droppings from chickens?

Over time, this waste adds up. In fact, if you could pile up all the livestock manure that’s produced in the United States in a year, it would weigh 350 BILLION pounds! You can see why lots of scientists are tackling this messy problem.

What do we do with all of this poo?

Farmers can use manure to fertilize their fields. Animal droppings might not look or smell pretty, but they contain important nutrients that plants need to grow.

Farmers spread their animals’ waste onto fields for the same reason that kids take vitamins to grow big and strong.

But there aren’t enough fields for all the waste that’s produced by animals. In fact, if too much manure is plowed into the soil, it can slide from hillsides and trickle into streams. This pollution can harm animals and people who depend on fresh, clean water.

So, Dr. Lima and Dr. Marshall got the idea to create something useful from manure. Dr. Marshall has already found uses for nut shells and other agricultural waste products.

The real magic behind the scientists’ research is lots of heat.

They have a special oven that they put the chicken droppings in that can reach over 1,300 degrees Fahrenheit. Ouch! That’s about three times hotter than your oven gets at home!

By adding all that heat, the waste becomes a big, dried-out sponge. It’s full of tiny holes, or pores, that can lock in and hold substances—like nasty chemicals or metals that might be floating in sewage water.

Along the way, Dr. Lima discovered that their sponge-like material was especially great at mopping up metals that can pollute water.

Called “heavy metals,” these Earth elements include substances like lead, mercury and arsenic. You may have heard of them. Most occur naturally in the world around us. But when large amounts of these metals or chemicals leak into water supplies, or into the soil, they can be harmful to people and wildlife.

There aren’t many materials around that can filter out the tiny, floating molecules from these hard-to-grab metals. That’s why Dr. Lima and Dr. Marshall were so excited to find that their super-heated chicken droppings made such a great mop.

“We found out that our material has a negative electrical charge, which enables it to cling to tiny molecules from positively-charged metals,” says Dr. Lima.

The burned-waste material owes its negative charge to phosphorus. Phosphorus gets into the chicken droppings because the animals eat special diets that contain this important nutrient. But chickens don’t digest all of the phosphorus in their meals, so some of it comes out in their waste. When the negatively-charged sponge material gets near metal molecules with a positive charge, the two are strongly attracted to each other.

Think of how two oppositely-charged magnets stick together. Or how magnets stick to the kitchen fridge. The scientists’ special filtering material works the same way. It clings to all the little positively-charged metal particles—like those from copper and zinc—which might be floating around in polluted water. This special filtering material might even be able to mop up mercury particles, which many researchers and health workers are worried about.

Just think—there may come a day when we can thank chickens for helping us clean up the environment!

—By Erin Peabody, ARS Information Staff.


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Last Modified: 8/12/2016
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