Biodiesel often is made from soybean or vegetable oil, with crude glycerin
the resulting by-product. This compound, which currently is used in such things
as hand lotions, cosmetics and shampoo, is a pure energy source.
According to Mark Honeyman, animal science professor and coordinator of Iowa
State's Research Farms, with an increase in biodiesel production comes a surplus
of crude glycerine.
Brian Kerr, an ARS research leader and collaborating associate professor of
animal science, directed the glycerin feed trials
Metabolism trail with laying hens
Kristjan Bregendahl, assistant professor of poultry nutrition, conducted a
metabolism experiment with 48 laying hens. Typical feed rations that included
corn, soybean meal, meat and bone meal, and four levels of crude glycerin - 0,
5, 10, or 15% - were fed to the hens to determine the energy value of the
"We found the energy in crude glycerin was used with high efficiency by the
hens," Bregendahl said. "And we saw no adverse effects on egg production, egg
weight, egg mass or feed consumption in this short experiment."
However, the consistency of the feed was an issue. Bregendahl described the
laying-hen diets that included 10-15% crude glycerin as "rather sticky."
Honeyman said that the 10% inclusion level of glycerol may be the upper
Caution when using glycerin
Another issue was that when biodiesel is produced from soybean oil, methanol
is used in the process. Methanol can be toxic, so Honeyman said swine and
poultry producers interested in trying glycerin as part of a feed ration would
need to work with the biodiesel plant to make sure methanol levels are below the
Food and Drug Administration approved level of 150 parts per million in the
Iowa State researchers, have a series of funding proposals in the works to
further examine the use of crude glycerin in diets for nursery and finishing
pigs, sows, broilers and layers.
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