Patents Show that an Abundant Plant Is a Focus as a Biofuel Feedstock

By Richard Maldanis, Ph.D., Nerac Analyst

As fuels derived from renewable resources take on a greater role on the global energy stage, it is critical that researchers continue to design novel ways to generate biofuels to meet this demand. Of those renewable resources, switch grass has many advantages as an ethanol source. In fact, a look at intellectual property disclosures citing novelties using switch grass for ethanol production shows that indeed researchers are examining this abundant source.

In January, Chemical & Engineering News reported that researchers from the University of Nebraska discovered that a net energy surplus resulted when switch grass was used as a feedstock for ethanol production. Their five-year study found that 540 percent more renewable energy was generated as compared to the energy needed to grow and harvest the switch grass feedstock. While a net energy surplus is one criterion that must be met to commercialize a feedstock for bioethanol production, other factors such as increasing the extractability of cellulose from the lignin matrix and the ability to ferment the sugars to ethanol must be enhanced for this conversion process to succeed in industry.

Three Companies Dominate Patent Activity

An examination of U.S. and International patents found 39 patents filed in the past five years dealing with ethanol generation from switch grass precursors. While switch grass is noted as a feedstock used in these inventions, other feedstock materials are claimed as well, including lignocellulosic feedstock sources such as wood, and waste agricultural fibers such as wheat straw and oat hulls. Currently, researchers are particularly interested in utilizing readily available and renewable biomass starting materials to generate ethanol. Of these, Iogen, EI du Pont de Nemours (DuPont) and Novozymes have the most patents disclosing novelties on this technology.

Iogen has nine patents, only one of which was filed in the United States. Most of Iogen’s disclosures were filed as European or World patent applications, an indication of where the company thinks the market will develop. Iogen patents disclose inventions for alternative methodologies to pretreat feedstock prior to ethanol formation as described in World Patent Application 2005099854/WO-A1. After treating a feedstock such as switch grass with hot concentrated sulfuric acid steam to reduce the material’s particle size, a metal sulfate impurity can form and become entrapped in the chemically treated feedstock. This can affect the transformation in fuel ethanol. One of Iogen’s patents describes a pre-treatment extraction method to recover these inorganic salts, which can then be used for fertilizers.

Pretreatment Is a Common Focus

Another Iogen invention claims novel ways to pretreat feedstock sources before ethanol formation (European Patent 01364072/EP-B1). This patent is based on reducing the amount of acid needed to pretreat feedstocks, because acid compounds can degrade xylose, an essential component in ethanol production. To create lignocellulosic feedstocks of suitable particle size for ethanol production, the patented methodology subjects the precursor to milling techniques that mechanically treat the biomass material.

One of DuPont’s more recent disclosures (the company has three World patent applications published between 2006 and 2007) also addresses treating biomass resources for ethanol formation. Published in 2006, World Patent Application 2006110900/WO-A2 describes a method of pre-treating biomass with ammonia compounds and digesting it with a saccharification enzyme to generate fermentable sugars. The fermentable sugar is then biocatalyzed by adding biocatalysts that include bacteria, filamentous fungi, and yeast to produce ethanol. The patent describes using switch grass, but the bio-source could also be wastepaper, corn cobs, corn husks, corn stover, wood chips, or animal manure.

Also assigned to DuPont is World Patent Application 2007149450/WO-A2 published in December 2007. The patent notes that bacterial growth is a concern of ethanol fermenters because microbe formation during the fermentation process can convert sugars to non-ethanol products including organic acids. This patent describes using chlorine dioxide to prevent microbe formation during cellulosic feedstock fermentation. It also states that switch grass or other biomass resources can be used in this process, including potatoes or whey.

Novozymes is also a player, having filed two World patent applications in 2006 involving ethanol formation from switch grass, focusing on ways to pretreat lignocellulosic material before fermentation. Cellulase and xylose isomerase can be combined in pretreating biomass materials to result in an increase in available five-carbon sugars. These sugars then can be fermented into ethanol using enzymes such as saccharomyces cerevisciae. The patent states that switch grass, as well as office paper, or pine wood can be used as the feedstock resource for this process.

Watch for Non-U.S. Patents

Through patent applications, researchers are currently disclosing ways to pretreat feedstock materials including switch grass to enhance the availability of cellulosic extractables. Most inventions were not filed in the U.S., so it is important for companies seeking to monitor their competitors to review international disclosures. Companies are most interested in increasing the amount of extractable five-carbon sugars as these have been shown to be most effective in fermentation to ethanol. Further R&D efforts on using switch grass for ethanol production is expected to continue as commercial interest grows in the generation of biofuels that use sources having a minimal impact on food production.