Corn - Photo Credit: MarS via Flickr
We at SDU are big fans of ethanol - if it is made from cellulosic materials. Corn ethanol is problematic. Making ethanol from corn consumes a lot of energy so the pay-off, or the net increase in energy, is small compared with other biofuels. To make corn based ethanol more energy efficient, researchers at Washington University are demonstrating a process used in breweries and wastewater treatment facilities: oxygen-less vats of bacteria that naturally feed on organic waste produced from the fermentation process.
This "new" process is one we have covered many times. (Link) The WU team is using a simple biodigester after the fermentation process. The biodigester uses bacteria in the absence of oxygen to produce methane.
As the bacteria break down waste, methane is released, which can be used to power the distillation process. The methane generated can offset much of the energy required to make ethanol.
From Technology Review:
Largus Angenent, a professor of chemical engineering, and his team at Washington University have tested anaerobic digestion on waste from ethanol plants and found that the process could cut down an ethanol facility's use of natural gas by 50 percent. The team has published the results in the recent issue of the journal Environmental Science and Technology.
Angenent says that the process would serve as a short-term solution until more-efficient biofuel, such as cellulosic ethanol, is commercially viable. "Rather than have hope for new technology that comes to fruition in 10 or 20 years, we need technology we can implement now," says Angenent, who recently became an assistant professor of biological and environmental engineering at Cornell University. "This is an interim process, and it's off the shelf."
Nearly all ethanol biofuel in the United States is made from corn. Typically, the ethanol production yields organic waste that is then consolidated into two parts: a dry, cake-like substance and a syrupy solution, called thin stillage, that's layered on top. The concoction is used as animal feed. Angenent says that a large portion of this feed, particularly thin stillage, which is laden with salts, provides low nutritional value but may have high energy potential for powering a plant when broken down via anaerobic digestion.
To test this theory, the researchers cultivated thermophilic bacteria from a wastewater treatment plant in two small, five-liter anaerobic digesters. Angenent and his colleagues then slowly began feeding waste samples into the digesters, which were kept at 55 °C to maximize the bacteria's activity. As the digesters ran, the team measured the amount of methane released.
Via: Technology ReviewCheck: Sustainable Design Update