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Ethanol By-Product Reprocessing Expands to Pilot Stage

Harvesting fungi (Jeni Maiers/Iowa State University)

Harvesting fungi from ethanol byproducts (Jeni Maiers/Iowa State University)

A process developed by engineers at Iowa State University in Ames to turn by-products of corn ethanol into into animal feed has moved from the lab to a pilot plant. The process, called MycoMeal, developed by engineering professor Hans van Leeuwen and his team, has two patents pending and won several industry and academic awards.

In this process, van Leeuwen’s faculty, postdoc, and grad student researchers produce a fungus — Rhizopus oligosporus – that makes a high-protein animal feed from the leftovers of ethanol production. The process of growing the fungus also cleans water from ethanol production so that the water can be recycled back into fuel production.

Ethanol production has leftovers, known as stillage, that contains solids and other organic material. Most of the solids are removed by centrifugation and dried into distillers dried grains that are sold as livestock feed. The remaining liquid, known as thin stillage, still contains some solids, organic compounds, and enzymes. Because the compounds and solids can interfere with ethanol production, only about half 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 Iowa State researchers add fungus to the thin stillage that grows quickly — in less than one day — into a thick mass. 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 rich in protein, 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 advanced from the lab to the Iowa Energy Center’s Biomass Energy CONversion (BECON) facility, located in Nevada, Iowa. BECON has large-scale conversion systems that process agricultural-related biomass into fuels and chemicals, and now animal feeds like MycoMeal. The team has begun using screens to harvest pellets of the fungus (pictured above) from the project’s 20-foot high reactor. They’re feeding some of the fungus pellets to chickens and will soon start feeding tests with hogs.

Van Leeuwen estimates the production technology can save U.S. ethanol producers up to $800 million a year in energy costs. He says the technology can also produce ethanol co-products worth another $800 million or more per year.

Read more: Prof Creates High-Value Chemicals from Biomass

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