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A Smooth Transition from Fuel to Feed

Published on 8 June, 2009, Last updated at 03:47 GMT
By Sandy Miller Hays
U.S. Department of Agriculture

It's often been said of the pig that you can use every part of that versatile animal except the squeal. Unfortunately, that's not always the case with production of other materials — biofuels being a prime example.

Biofuel research isn't just a matter of finding the right basic ingredient, whether that's corn, soybeans or grass cuttings. The scientists also have to figure out what to do with all the "leftovers" that result from turning natural products into fuels.

And there can be mountain upon mountain of those leftovers. For example, in the Midwest alone, the production of ethanol generates 10 million tons of dried distillers' grains left over after grain such as corn or sorghum is converted into ethanol.

The same type of byproduct surplus can occur with the production of biodiesel from soybeans. Producing a gallon of biodiesel from soybean oil yields around two-thirds of a pound of crude glycerin. The good news is that this glycerin can be refined to 99 percent purity and used in a wide variety of products, including pharmaceuticals, foods, drinks, cosmetics and toiletries.

And now, it seems, you can use the leftovers from biofuel production to make... more pigs! (And chickens, too, for that matter.)

That's according to the scientists of the Agricultural Research Service (ARS), who have teamed up with university colleagues to see whether crude glycerin could be used to supplement livestock feed. They wanted to take a look at using the coproducts of biodiesel production as feed supplements because no such data was available to the livestock industry.

Livestock and poultry producers are always looking for ways to supplement their animals' feed while saving money and boosting nutrition. Some scientists have shown that it's possible to supplement pig diets with the dried distillers' grains left over from ethanol production, but the downside is a potential increase in manure production — and higher levels of volatile organic compounds in the manure, which can increase the odor emissions.

To test crude glycerin's potential as a feed supplement, the ARS scientists fed it to pigs at different stages of growth in five different experiments. The pigs that ate the crude glycerin were able to digest it efficiently, and it gave them just as much caloric energy as did corn grain.

A followup study showed no adverse effects on weight, carcass composition and meat quality in pigs that ate diets containing either 5 percent or 10 percent crude glycerin from weaning until they were ready to head to market.

The ARS scientists and their university partners also looked at the potential of crude glycerin as an additive to poultry feed. They used 48 laying hens and 1,392 broilers in four different studies.

After feeding four levels of crude glycerin to the laying hens, they compared the birds' feed consumption, egg production, egg weight and egg mass (that's calculated by multiplying egg production by egg weight). They found no significant differences among the four groups. Similar positive results were garnered in the three studies with the broilers.

The bottom line, according to the ARS scientists: Crude glycerin is an excellent source of energy in swine and poultry diets and can be used without harming the animal's performance, carcass composition and meat quality.

From a nutritional standpoint, using glycerin in this way provides an alternative dietary energy source that could lower feed costs (and perhaps meat costs, if we're lucky).

This isn't entirely a "done deal" — there are still questions to be resolved. For example, crude glycerin contains small amounts of methanol and salt, which could potentially limit its use as a feed supplement. Additional studies may be needed to assess how much methanol the livestock can safely consume in glycerin supplements, which would help regulators refine the U.S. standards for using crude glycerin in livestock feed.

But as our national thirst for biofuels continues to grow, using crude glycerin supplements in livestock and poultry feed could be a win-win situation for biodiesel producers and farmers alike. The ARS scientists say swine and poultry producers are already very interested in supplementing their animals' feed with glycerin.

Imagine that: a way to use crops for fuels and feed at the same time!


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