With higher energy content and better blending compatibility with gasoline than ethanol and widespread applications for synthesis of chemicals and polymers, it’s no wonder that bio-based butanol has created a lot of buzz.

In addition to an energy density 48 percent greater than ethanol, butanol has a lower vapor pressure, is less susceptible to water contamination, and is less corrosive – properties that make it more attractive for use in the existing transportation infrastructure, including pipelines, storage tanks, and vehicles.

In August 2005, Ohio inventor and entrepreneur David Ramey drove his ’92 Buick Park Avenue 10,000 miles across the U.S. exclusively on 100 percent butanol.

He averaged 24 miles per gallon, beating his average of 22 miles per gallon on gasoline. Ramey wanted to prove that bio-butanol was a superior alternative to ethanol. “That event demonstrated to the public that a power-grade fuel alcohol made from corn is already available – butanol – with the potential to replace gasoline, gallon for gallon,” he wrote afterwards.

Since then, this alternative fuel has made great strides. In 2012, the U.S. EPA approved 16 percent butanol blending in gasoline and 20 percent blending in diesel fuel. That same year, a 24 percent bio-butanol gasoline blend was used at the Olympic Games in London.

Besides its use as a fuel, butanol is used as a building block to make chemicals for the $85 billion paints and coatings market and the $700 billion polymers and plastics market. Industry also uses butanol to produce key derivatives, including acrylates, acetates and glycol ethers. Two different isomers of butanol are most common – n-butanol, a straight chain molecule; and iso-butanol, a branched molecule. Each has similar fuel properties but different applications in the chemical industry.

Given its versatility, it is not surprising that small and large companies worldwide are racing to scale up this renewable source of butanol.

The big players include Butamax (U.S. – U.K.), Gevo (U.S.), Cobalt Technologies (U.S.), and Green Biologics (U.K.), Cathay Industrial Biotech (China), Metabolic Explorer (France), and Tetravitae (U.S., now part of Eastman Chemicals).

Smaller companies are also offering innovative solutions including Optinol, Microvi Biotechnologies, Butrolix, Elcriton, Calysta, Butalco, EnerGenetics, and Gourmet Butanol. Ramey’s company, Environmental Energy, became Butyl Fuel, which later merged with the biotechnology company Green Biologics and focused on butanol and other four-carbon bio-based chemicals.

Bio-based butanol was first discovered in 1862 by famed microbiologist Louis Pasteur. Microbes capable of producing acetone, butanol and ethanol (A-B-E) were used industrially as early as 1902, to make solvents and for making synthetic rubber and cordite (smokeless gunpowder). The A-B-E fermentation went on to become the second largest fermentation industry next to ethanol. A-B-E was viable until the 1950s, when the industry could no longer compete with the lower cost of the petroleum-derived molecules.

The Butanol Isomer Family

Today’s bio-butanol companies have several advantages. First, they can leverage the existing highly efficient infrastructure for corn ethanol. Second, companies in the 1950s were limited to naturally occurring strains. New tools in metabolic engineering, better controls for the fermentation, and improved methods for solvent recovery have improved efficiency. Third, new material markets, combined with better life-cycle performance, government incentives and higher oil prices have improved the economic opportunities for bio-butanol.

The example was set by Butamax and Gevo, arguably the most contentious rivals in advanced biofuels. In 2010 Gevo collaborated with ICM to acquire and retrofit an 18 million gallon per year ethanol plant from AgriEnergy in Luverne, Minn., for isobutanol production. Butamax, a joint venture between BP and DuPont formed in 2009, partnered with Highwater Ethanol LLC, to retrofit a 50 million gallons per year corn ethanol plant in Lamberton, Minn., to produce isobutanol in 2011.

Butamax has engaged ten other ethanol facilities, with a combined production capacity of up to 900 million gallons per year, as part of an Early Adopter Group for its technology. It’s not the first time the two companies have taken similar strategies. Both have invested in metabolic engineering, microbial strain improvement, and solvent separation technologies: advances at the heart of an extensive patent dispute.

Advances in cellulosic technology and the availability of other feedstocks will further expand opportunities for bio-butanol and its derivative products. This little four-carbon molecule could very well end up a giant in the future bio-economy.




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