Iowa State University engineering professor Hans van Leeuwen is leading a research team that has developed a process that uses a fungus to make a high-protein animal feed from the leftovers of ethanol production.
Growing the Rhizopus oligosporus fungus also cleans the water used in the ethanol production process so that it can be recycled back into fuel production. The process, called MycoMeal, could one day produce a low-cost nutritional supplement for people.
For every gallon of ethanol produced, there are about five gallons of leftovers known as stillage. The stillage contains solids and other organic material. Most of the solids are removed by centrifugation and dried into dried distillers 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. But because the compounds and solids can interfere with ethanol production, only about 50 per cent of thin stillage can be recycled back into ethanol production. The rest is evaporated and blended with dried distillers grains to produce dried distillers grains with solubles.
To resolve that issue, the researchers add the fungus to the thin stillage and it feeds and grows into a thick mass in less than a day. The fungus removes about 60 per cent 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 is rich in protein, certain essential amino acids and other nutrients. It can also be blended with dried distillers grains to boost its value as a livestock feed and make it more suitable for feeding pigs and chickens.
Van Leeuwen said the production technology could save US ethanol producers up to $800m (£494.5m) a year in energy costs. He also said the technology can produce ethanol co-products worth another $800m or more per year, depending on how it is used and marketed.
Now that the project has moved from a campus lab to the Iowa Energy Center’s BECON facility in Nevada, van Leeuwen said researchers are working to improve the process at larger scales.
Even so, the process has been refined enough already so that the researchers can use simple screens to harvest pellets of the fungus from the project’s 20ft-high reactor. Currently, the researchers are feeding some of the fungus to chickens and will soon start feeding tests with pigs.
As the project has been successfully scaled up, so has van Leeuwen’s optimism that the process could significantly help the biofuels industry.