The City of Seattle has completed its isobutanol blended gasoline pilot project on its fleet vehicles and is gearing up for phase two of the pilot. The city reduced carbon emissions at its Cedar Falls location by 33% during phase one of the pilot, which consisted of using the gasoline blend on four standard combustible engine vehicles for four months.

The city used a blend of 20% Gevo renewable isobutanol with 80% gasoline to reduce carbon intensity levels. The blend costs about $1.50 per gallon above the cost of conventional gasoline.

"The outcome of the trial was overwhelmingly positive. The testing vehicles saw no adverse effects on their engines, filters, driving performance, driver satisfaction, nor the existing fuel pipelines. We are now ready to move to a higher blended fuel and begin Phase II ahead of schedule,” said Timothy  Cesarek, chief commercial officer of Gevo, in a release.

For the second phase, set to begin within two months, the same vehicles will be tested using 50% renewable content to further reduce carbon levels, although not all the renewable content will be isobutanol, according to Gevo. Gevo’s goal is to replace 100% of each gallon of gasoline with renewable content.

Philip Saunders, green fleet program manager for Seattle, stressed that fleet electrification is still the city’s No. 1 goal for its fleet. If all goes well, the city will use renewable gasoline on emergency vehicles.

“For most people in the fleet business, they know emergency and police vehicles are using the most fuel,” Saunders said. “This would definitely affect our carbon footprint.”

The City of Seattle’s goal is to reduce fleet emissions by 50% by 2025. It was awarded the 2019 Green Fleet Award, ranking No. 4.