Ultrasound can improve biodiesel production

Researchers at Iowa State University have begun experimenting with the use of sound waves in the creation of biodiesel. The team involved is exploring whether high-frequency sound waves can be used to successfully break down plant matter for the creation of high grade biofuels.

Associate professor of agriculture and biosystems engineering, David Grewell, is leading the team involved in the research. So far the research has successfully demonstrated that using ultrasound to pretreat certain feedstocks can lead to enhanced chemical reactions. These chemical reactions are a necessity in terms of converting the feedstocks into biodiesel products and other chemicals. The plant matter that has responded successfully to this process includes corn stover, soft wood and switch grass.

The process enables lignin - the chemical compound in plant cell walls that binds hemicellulose and cellulose together - to be removed in a solution more efficiently. Lignin is usually removed from biomass by the use of enzymes or chemicals. The sugars that are freed by lignin removal are then able to be dissolved ready for processing into biofuel products.

The researchers found that using high-frequency sound waves instead of chemicals or enzymes for lignin removal is a superior method as it enables the freed sugar to dissolve in minutes. With traditional methods, the sugar can take hours to dissolve to a state that it is ready for further processing.   

Researchers also found that ultrasound can speed up the hydrolysis of corn starch as it breaks the corn down into smaller fragments, in comparison to the traditional method of steaming. The smaller fragments are then broken down better by the enzyme process, which is used to release glucose for fermentation.

Ultrasound has also been found to accelerate transesterification, which is the principal chemical reaction involved in turning oil products into biodiesel. The researchers found that soybean oil was able to be turned into biodiesel in under a minute when subjected to ultrasound, in comparison to the 45 minutes the transformation takes using traditional methods.