This bill amends the Clean Air Act to revise provisions concerning alternative fuel.

Currently, a change to the original configuration of a certified vehicle or engine, including alternative fuel conversion, may be a potential violation of the Act's prohibition against tampering with devices used to control emissions from vehicles. The bill prohibits the aftermarket conversion of a vehicle to alternative fuel operation from: (1) being considered tampering under the Act if the conversion technology is matched to an appropriate vehicle and does not degrade emission performance, or (2) requiring the issuance by the Environmental Protection Agency (EPA) of any certificate of conformity. The bill also establishes labeling requirements for an aftermarket conversion.

The EPA may not prohibit or control biomass fuel under the Act. Biomass fuel is produced by conversion of certain organic matter which is available on a renewable basis.

If a fuel choice enabling manufacturer (certain manufacturers of vehicles that operate with alternative fuels) is in compliance with applicable fuel economy standards, the vehicles it makes are deemed to be in compliance with greenhouse gas regulations established by the EPA under the Act. The requirements governing the calculation of average fuel economy are revised, including by giving an average fuel economy bonus for those manufacturers.

The bill amends the Internal Revenue Code to adjust the excise tax on liquefied natural gas to 24.3 cents per energy equivalent of a gallon of diesel.

The Clean Air Act places Reid vapor pressure limitations, or gasoline volatility limits, on gasoline during the summer ozone season. Gasoline blended with 10% ethanol (E10) may exceed this limitation by a certain amount under the Act. The bill extends this waiver to gasoline blended with more than 10% ethanol.