The rapid expansion of ethanol and biodiesel plants has led to questions about the use of byproducts from alternative fuels.

So far, the use of ethanol byproducts in animal feed has garnered the most attention. But researchers at Iowa State University and the USDA’s Agricultural Research Services (ARS) are studying a biodiesel byproduct in swine and poultry feed.

“With an increase in biodiesel production comes a surplus of crude glycerin,” says Mark Honeyman, animal science professor and coordinator of Iowa State’s Research Farms.

Crude glycerin is a pure energy source currently used in hand lotions, cosmetics and shampoos.

“With an increase in ethanol, comes higher corn prices,” he says. “Since corn is fed to pigs primarily for its energy value, we’re studying the possibility of replacing corn with glycerin in swine feed.”

Brian Kerr, ARS research leader based at Ames, IA, conducted glycerin feed trials. In a metabolism study, both nursery and finishing pigs were fed levels of 5, 10 and 20% glycerin. Pigs readily consumed glycerin and energy value was similar to corn.

Since 20% glycerin won’t flow well in a dry feeder, the 10% inclusion level may be the upper limit, Honeyman says.

Results are pending on the impact of glycerin on meat quality.