Companies reach for process improvements

By Holly Jessen | April 15, 2010
The ethanol industry continues to aim for efficient and environmentally sound production methods. In March, two companies, Poet LLC and Biodynamics Inc., a newly formed coproduct enhancement developer, announced projects to reduce water use in ethanol production, and Didion Ethanol LLC embarked on a yearlong project to reduce energy consumption by 25 percent.

The first goal of Poet's new sustainability initiative, Ingreenuity, will be to cut water use for ethanol production by 22 percent over the next five years. If successful, that adds up to an annual water savings of 1 billion gallons. Poet engineers developed a total water recovery process to recycle cooling water, rather than discharging it. The system has been installed in three Poet plants, which now average 2 to 2.5 gallons of water per gallon of ethanol. The company is also looking into offering its total water recovery process to other ethanol producers.

In 2009, Poet plants used an average of 3 gallons of water for every gallon of fuel producedan 80 percent reduction from 1988, when the company started producing ethanol. In addition, several plants use alternative sources of water, such as water recycled from other industries or waste water treatment plants.

Poet plans to go beyond just reducing water use at the company's ethanol plants. Feedstock producers will be surveyed to determine how much irrigation is used. In addition, over the next five years, Poet will donate more than $420,000 to a non-profit, Global Health Ministries. Part of the money will be used to repair, construct and maintain 90 water wells in Nigeria.

Iowa-based Biodynamics announced two Midwest ethanol plants have agreed to let the company install production units using fungi to process thin stillage, recycling water and creating a new single-celled protein coproduct. Biodynamics will finance, install and operate the technology in demonstration units at the unnamed dry mill facilities. The company expects commercial scale testing to be completed in the third quarter of 2010.

The fungus, Aspergillus oryzae, is commonly used to treat industrial waste water, said Trevor Cassel, project director for Biodynamics. In the ethanol process, it will remove organic solids from the thin stillage, leaving water that is clean enough to be used again, reducing water use by 75 percent. The company says to create 2.8 gallons of ethanol, the process uses only 2.1 gallons of water. In addition, one bushel of corn will result in 13.5 pounds of distillers grains and 3.5 pounds of the coproduct coming from the thin stillage treatment. That coproduct could be used as a meat substitute for human consumption in some settings, but Biodynamics will use it as animal feed.

In Courtland, Wis., Didion Ethanol began an $11 million project to save energy by increasing the efficiency of its evaporators and dryers, said Chad Carter, plant controller. The energy efficiency project at Didion includes four dryer projects and two evaporator projects. The company is adding corn oil extraction to reduce the load on the dryers, meaning distillers grains can be dried more efficiently and with less energy. Didion will also add two centrifuges and a second whole stillage tank and upgrade the conveyor system. This will allow stockpiling of stillage so it can be fed into the dryer at 100 percent capacity, Carter explained. By adding fermentation capacity, the company hopes to increase the amount of corn solids being turned into ethanol by 3.8 to 5 percent, while also reducing the load on the dyers. Finally, the company will optimize the dryer's fluid bed by re-piping and re-engineering it so it is fed just enough air to function properly. On the evaporation side, Didion will add a fourth evaporator to lower overall temperatures and reduce energy use. Finally, Didion will replace the liquid jet eductor in the evaporator with a liquid ring vacuum pump that will cut energy use in half.