The “Blending Wall”: US Lacks Infrastructure for more Bioethanol use

A study by Purdue University finds that the US has hit the “Blending Wall” needs more infrastructure to increase bioethanol use; if this problem isn’t solved then federal targets will be missed.

The “Blending Wall” refers to the saturation of ethanol demand in fuel. Most bioethanol use is from blending it with gasoline, but there is a limit on how high this blend can go without modifying the engines of the cars it is used in. Flex-fuel vehicles using E85 fuel are another consumer, but the numbers of these are low, making up just over 3% of all vehicles on the road in the US. To compete for mileage with gasoline, E85 would have to be produced far more cheaply than gasoline as E85 is less energy dense.

The US currently has around 2,000 E85 pumps, but to meet the targets for 36 billion gallons of renewable fuel a year by 2022 the US will need 2,000 new pumps a year according to the study. As numbers of flex fuel cars increase the rate of increase in the number of these stations will increase as well, but this will take time. Currently ethanol content in fuel is capped at 10% ethanol but an increase to 15% is being considered, but even if this happens the “Blending Wall” will be reached again in 4 years.

Ethanol alone can’t be used to meet these targets: Biobutanol production is increasing and can be used in blends with gasoline. Biodiesel is similar enough to petro-diesel that it can be used in conventional diesel engines without engine modification or blending, avoiding the infrastructure and blending wall problems of bioethanol. Other biofuels are under development, for example conversion of biomass to chemicals so similar to gasoline that infrastructure and blending is no longer an issue.