Ethanol leftovers: From fungus to feed

IOWA STATE (US) — Fungus grown from ethanol leftovers is being used to make animal feed. Researchers believe it may be possible to develop the process further to be used as a low-cost nutritional supplement for people.

The production technology, called MycoMeal, has the potential to save U.S. ethanol producers up to $800 million a year in energy costs and could produce ethanol co-products worth another $800 million or more per year, depending on how it is used and marketed.

“We’re learning we can reliably produce good quality and good quantities,” says Hans van Leeuwen, professor of engineering at Iowa State University.

For every gallon of ethanol produced, there are about five gallons of leftovers known as stillage that contains solids and other organic material. Most of the solids are removed by centrifugation and dried into grains that are sold as livestock feed, primarily for cattle.

The remaining liquid, known as thin stillage, still contains some solids, a variety of organic compounds and enzymes. Because the compounds and solids can interfere with ethanol production, only about 50 percent of thin stillage can be recycled back into ethanol production. The rest is evaporated and blended with distillers dried grains to produce distillers dried grains with solubles.

The researchers add fungus to the thin stillage and it feeds and grows into a thick mass in less than a day—what van Leeuwen calls “lightning-speed farming.”

The fungus removes about 60 percent of the organic material and most of the solids, allowing the water and enzymes in the thin stillage to be recycled back into production.

The fungus is then harvested and dried as animal feed that’s rich in protein, certain essential amino acids and other nutrients.

It can also be blended with distillers dried grains to boost its value as a livestock feed and make it more suitable for feeding hogs and chickens.

The project has moved from a campus lab to the Iowa Energy Center’s Biomass Energy Conversion (BECON) facility in Nevada, where van Leeuwen says researchers are working to improve the process at larger scales.

“We’re adding and subtracting, doing things differently and redesigning our process all the time,” he says.

The process has developed enough that researchers can use simple screens to harvest pellets of the fungus from the project’s 20-foot high reactor. They’re feeding some of the fungus to chickens and will soon start feeding tests with hogs.

A next step could be testing the fungus for human consumption. (University leaders have tried the fungi and researchers regularly eat it).

“Implementation of this process addresses criticism of biofuels by substantially lowering energy inputs and by increasing the production of nutritious animal feed,” van Leeuwen says. “The MycoMeal process could truly revolutionize the biofuels industry.”

Fungi grown on the leftovers of ethanol production. (Credit: Jeni Maiers)

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