Bioisobutanol as a Gasoline Additive Receives Big Boost

On June 12, EPA Administrator, Scott Pruitt, in a letter to Butamax Advanced Biofuels LLC, a joint venture of BP and DuPont, announced the registration of isobutanol (a 4 carbon alcohol) as an additive for blending into gasoline up to a maximum 16 volume percent. This ruling fell under what is known as the OCTAMIX waiver granted by the EPA in June, 2012 allowing a variety of alcohols to be blended into gasoline at up to an oxygen concentration of 3.7 wt.%. This translates to the 16 vol. % for isobutanol, also known as isobutyl alcohol (iBA)

When iBA is produced from renewable resources, the prefix bio in added to its designation and as such bioisobutanol qualifies as a renewable fuel under the Renewable Fuel Standard (RFS). With the properties of isobutanol closer to gasoline than ethanol it has several significant advantages over ethanol as a gasoline blend component:

  • Its energy content is 25 % higher than ethanol and only 82% of gasoline on a volumetric basis. With its higher density than gasoline, when blended at 16 vol.%, fuel consumption increases by only 3.5%.
  • Isobutanol has a lower blending vapor pressure than ethanol and does not increase the vapor pressure of gasoline at any blending level. The 1 psi Reid Vapor Pressure (RVP) summer time exception that ethanol enjoys need not apply with iBA. Furthermore refiners may be able to use less expensive, lower vapor pressure blend stock with iBA.
  • With gasoline/iBA blends, no phase separation occurs if any water is present. This means that iBA can be blended at the refinery and transported safely in pipelines. This is contrasted with ethanol’s affinity for water which could result in harmful potential phase separation with any moisture present. Due to its polarity, ethanol is typically splash blended at terminals.
  • While iBA’s blending octane is not as high as ethanol’s, its Research Octane Number (RON) of 114 and Motor Octane Number (MON) of 94 (R+M/2 = 104) is more than adequate for production of regular to high octane gasolines.

Butamax Advanced Biofuels LLC (Butamax) has developed and patented technology for producing isobutanol from fermentable sugars. Another company that can benefit from this latest EPA ruling is Gevo Inc. They have developed a yeast biocatalyst to produce isobutanol from fermentable sugars at high concentration and yields.

For several years there was a patent dispute between Butamax and Gevo which was ultimately settled and all litigation ended in August, 2015 when Butamax and Gevo entered into a global patent cross licensing and settlement agreement in order to accelerate development of markets for bio-based isobutanol. Under the agreement, Butamax and Gevo have cross licensed all of their respective patents to each other. Among other items, it was agreed that Butamax will take the lead in licensing bioisobutanol for any on-road gasoline blendstocks while Gevo will take the lead in licensing any application of bioisobutanol for ATJ (Alcohol-to-Jet Fuel) with each party and sub-licensees paying royalties to the lead party.

Soon after the formation of the Butamax joint venture by DuPont and BP, a demonstration plant was built in the UK and a fermentation laboratory in Brazil was used for testing their technology. In April, 2017, Butamax acquired the 10 million gal/yr. Nesika Energy ethanol plant in Scandia, Kansas and started detailed engineering to add the production of bioisobutanol.

Gevo, in collaboration with ICM, Inc. retrofitted a 1 million gal/yr. ethanol plant in St. Joseph, Missouri for production of bioisobutanol. They have also purchased the Agri-Energy, LLC 15 million gal/yr. ethanol facility in Luverne, Minnesota. This plant has a separate 1.5 million gal/yr. line dedicated to isobutanol. While Gevo is currently concentrating on ethanol production, eventual plans are to convert the entire plant to the production of bioisobutanol.

Most of the isobutanol produced at Luverne is likely destined for eventual conversion into synthetic jet fuel at Gevo’s jointly operated (with South Hampton Resources) biorefinery in Silsbee, Texas. See my Dec. 13, 2016 blog, Renewable Jet Fuel Tested on a Commercial Airline, for a description of how isobutanol is converted into synthetic jet fuel (ATJ).

The recent EPA ruling may encourage other companies to retrofit their ethanol plants for bioisobutanol production. In 2011, Butamax formed an Early Adopters Group (EAG) which consists of 10 ethanol facilities with 750 million gal/yr. of ethanol production volume. The companies in the EAG are likely candidates for conversion to bioisobutanol.

Prior to the recent ruling, the EPA had approved isobutanol blending in gasoline at 12.5 vol% (2.7 wt.% oxygen content). At this lower level, and with comparative prices for bio isobutanol and ethanol, the economics were somewhat questionable compared to ethanol blending at 10 vol%. This was even with refiners earning higher Renewable Fuel Standards (RFS) credits for blending bioisobutanol versus ethanol: respectively 1.3 RINs/gal versus 1.0 RINs/gal.

Now, however, with bioisobutanol blending allowed at 16.0 vol.% (3.7 wt.% oxygen content), the economics should shift more favorably to bioisobutanol especially with its other advantages compared to ethanol as outlined above. This will be enhanced as both Butamax, Gevo, and perhaps other existing ethanol producers ramp up production of bioisobutanol, thereby insuring amble supplies for refiners to blend.

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