Ultrasound improves biofuel production

Pretreatment technique reduces processing time and increases efficiency

US Engineers have used ultrasound to significantly improve the production of biofuels such as ethanol and biodiesel from feedstocks such as switch grass, corn stover and soft wood.

Researchers from Iowa State University pretreated the feedstocks with high-frequency sound waves to “break down” plant materials and found that the process consistently enhanced the chemical reactions necessary to turn them into biofuels.

In one instance, the technique was shown to increase the efficiency of removing lingin, a chemical which binds plant cell walls, in solution. Usually, enzymes or chemicals are used to remove lingin in a process which dissolves sugars into the biofuel and lasts hours. The dissolution process was reduced to minutes once pretreated with ultrasound.

In the production of ethanol, use of ultrasonics “greatly accelerated” the the hydrolysis of corn starch by replacing the jet cookers normally used to produce a mash for processing. The corn was sonically smashed into tiny particles in the same way that surgeons use ultrasound to shatter kidney stones. The smaller corn fragments created a greater surface area  for enzymatic action, resulting in fermentation yields comparable to jet cooking.

A further application in biofuel production was the use of ultrasound to accelerate transesterification, the main chemical reaction for converting oils to biodiesel. In the production of biodiesel from soybean oil engineers reduced the time from 45 minutes to less than one.

Researcher lead, David Grewell, associate professor of Agricultural and Biosystems Engineering at Iowa State University, said: “Economic models have shown that once implemented this technology could have a payback of less than one year.”