Isobutanol comes to light as a new, corn-derived ‘drop-in' fuel

By Sara Wyant

© Copyright Agri-Pulse Communications, Inc.

WASHINGTON, May 2, 2012 -Recent attention in the media and across the biofuels industry ‑ particularly that related to an advanced biofuels refinery set to open in Minnesota next month ‑ is putting a new spotlight on isobutanol. It's an alcohol fuel that can be made from corn and has “drop-in” attributes, meaning it can be used in engines that do not require modification.

Theoretically, isobutanol can be burned at up to a 16% blend rate with gasoline, more than the 15% restriction currently imposed by EPA on ethanol blends - and that rate (E15) is allowed only for cars or light trucks built in 2001 or later. E15 is not allowed for use in older vehicles, motorcycles and off-road vehicles, as well as in marine engines and small engines, like those used to power lawn mowers, weed trimmers and other gas-powered equipment.

Isobutanol is said to have more energy than ethanol and because it is a “drop-in” fuel, it poses no risks to engines from which E15 is currently barred by the EPA.

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The National Marine Manufacturers Association released a report in November 2011 that showed after testing for emissions and performance in a harsh marine environment, isobutanol has “great promise” as a petroleum blendstock for the boating industry. The results were encouraging enough for one official with the trade group to call isobutanol “the fuel of the future.”

The marine engine industry has a vested stake in the research, being one of the groups fighting EPA's implementation of the E15 waiver allowing the restricted use of the higher ethanol/gasoline blend. The industry fears the accidental introduction of E15 into a boat engine could cause permanent damage.

Adding to the argument for isobutanol is research presented in 2009, scientists with the DOE's Argonne National Laboratory in Illinois tested isobutanol in motor vehicle engines and said the fuel “may prove to be a more attractive alternative than ethanol due to fuel characteristics that closely resemble gasoline.”

Isobutanol, researchers say, does not absorb water like ethanol; has not been shown to date to cause corrosion in engine parts; and it evaporates much more slowly than ethanol. Isobutanol provides greater energy than ethanol, though it still comes in at about 17% less than gasoline (compared to ethanol's 20-25% reduction in energy compared with gasoline). Still, because it mixes well with gasoline, it can be sent through existing pipelines (ethanol requires a separate infrastructure).

So, is isobutanol the wider solution for getting beyond the limitations currently imposed on ethanol? Is it a better crop fuel destination for corn growers than ethanol?

One of the few complaints with isobutanol is its slightly lower octane rating than ethanol, suggesting it needs to be blended with gasoline that has a higher rating - a potential hurdle to wide distribution of isobutanol to gas pumps.

But Andy Aden, a bioenergy facilities expert at the National Renewable Energy Laboratory in Golden, Colo., says he does not believe the isobutanol octane level is a hurdle for blending.

“While it's not as high as ethanol (112-113), it is still relatively high compared to gasoline,” Aden said. “Isobutanol has an octane rating of 102 and gasoline is in the range of 91-99.” The differences are not so great that the lower octane rating outweighs the benefits of using isobutanol, he said.

Furthermore, Aden noted that ethanol has issues with Reid vapor pressure (RVP), a common measure of the volatility of gasoline. Refiners can more readily manipulate isobutanol blends for RVP, depending upon the time of the years - high RVP is needed for easier starting in winter months, while low RVP in summer averts the possibility of vapor lock and a disabling of the vehicle's fuel pump.

From a production standpoint, Aden says isobutanol poses greater toxicity, meaning it more quickly kills the organism used to ferment sugars into fuels and bio-based products. That requires a greater occurrence of process shutdowns to replace organisms. In turn, he said, that reduces yield, noting that theoretically, ethanol plants produce .51 grams of ethanol per one gram of sugar, while isobutanol facilities produce .41 grams of their product for each gram of sugar, a 20-percent decline.

However, Aden says research continues and the technology advances to reduce that difference. He said one way to bring down costs is to convert existing ethanol plants to isobutanol production rather than build a new plant. Another, he said, is to sell to multiple higher-end markets - isobutanol is a valuable platform intermediate for jet fuels and commodity chemicals.

One organization betting on the development of isobutanol is Gevo, a Colorado-based biofuels company that is reportedly putting some $40 million into the conversion of a 22-million-gallon-per-year, Luverne, Minn., ethanol plant into what the company says will be the first commercial-scale, corn-to-isobutanol plant in the country. Set to open the plant next month, Gevo plans to produce 18 million gallons annually and has said it hoped to sell isobutanol to other industries make other products. In December 2011, Gevo agreed to provide Coca-Cola with isobutanol to make a chemical to be used in the creation of a bottle derived from plant material.

Gevo, which is the first company to register isobutanol as a fuel with EPA (the company is in a legal dispute with BP and DuPont's Butamax alleged patent infringement), also has struck a deal to provide marina's with marine fuel.

Aden says expanding the use of isobutanol to include widespread gasoline blends could come within a few years. But he sees it as one of many options. “The greater variety of fuel choices for consumers, the better off we'll be,” he said.


Original story printed in May 2nd, 2012 Agri-Pulse Newsletter.

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