Renewable diesel is in use among numerous government agencies along with West Coast and elsewhere, but renewable gasoline is still mostly unheard of. The City of Seattle experimented with the fuel last year in an effort to reduce petroleum fuel use, finding a 33% reduction in carbon emissions during a pilot using a blend of renewable isobutanol and gasoline.

What is renewable gasoline and what does its development and use mean for government entities looking to reduce emissions?

According to Austin Vaillancourt, business development manager for Gevo, a producer of the renewable gasoline that Seattle uses, there are various blends of renewable gasoline. The company produces a 16% isobutanol blend (blended with 84% gasoline) and is developing RG50, a 50% blend of isooctane.

“We're further developing additional products with the objective of replacing the whole gallon of gasoline with 100% renewable gasoline in the coming years,” Vaillancourt said

Understanding Isobutanol Blends

Vaillancourt said isobutanol is ideal for blending with gasoline because of its low reid vapor pressure, above-average octane, and superior energy density. In comparison to ethanol-blended gasoline, isobutanol results in fewer operational issues associated with water solubility, materials compatibility, and corrosion, he said. This low water solubility and low oxygen content means a higher fraction of isobutanol and gasoline can be blended for the same oxygen content that ethanol would provide.

“This product is being used today in ethanol-free gasoline markets,” he explained. These are markets throughout the country that do not want ethanol in their gasoline but must comply with the Environmental Protection Agency’s reformulated gasoline regulations that require oxygenation. This includes in transportation, marine applications, and small engines.

Developing Higher Isooctane Blends

The second renewable gas option is isooctane, a 50% blend, which is currently in development.

“In the case of our renewable isooctane, there literally is no difference to gasoline,” Vaillancourt said. That’s because it’s a pure hydrocarbon molecule already present in gasoline and is used to make premium-grade gasoline, he explained.

Its blending advantages include low reid vapor pressure, excellent octane, and high energy density.

Vaillancourt said the company is developing the higher isooctane blend to meet demand from the public sector. “With municipal fleet managers and in municipal markets, they have their own mandates to reduce the greenhouse gas emissions within their fleet. So we have to be able to provide a fuel that has a higher renewable fraction than 16% in order to meet their goals,” he explained.

Where and When Is it Available?

Gevo is based in Luverne, Minn., where the isobutanol is manufactured using local corn. This then gets sent to a facility in Texas, which converts the isobutanol to isooctane and jet fuel. Blending with gasoline takes place in various locations, depending on use — for Seattle, it’s blended in that region, Vaillancourt said.

The fuels are both available to the City of Seattle under a long-term contract as well as a company that supplies fuel to Formula One racing vehicles and for outdoor equipment. Just with its current contracts, the company has reached its current production capacity. However, fleets looking to test out the fuel might be able to.

“There are opportunities for demonstrations with various fleet owners, but volumes beyond that are going to have to come from future expansions planned in 2020 and 2022,” Vaillancourt said.

Although Vaillancourt declined to state how much both fuels would cost, in its pilot, the City of Seattle paid $1.50 more per gallon for the isobutanol blend than it would regular gasoline. Vaillancourt said the company is hoping RG50 will be covered under low carbon fuel credits available in California and Oregon, which could significantly reduce the cost of the fuel.

Once it ramps up production this year, Gevo plans to deliver about 200,000 gallons of isobutanol to the City of Seattle. Once blended, this would result in 1.2 million gallons of fuel. Additionally, Gevo will deploy RG50 to help Seattle further reduce its carbon emissions, following a pilot of the second fuel.