20/20 Biofuels Challenge Act of 2005

20/20 Biofuels Challenge Act of 2005 - Directs the Administrator of the Environmental Protection Agency to promulgate regulations ensuring that motor vehicle fuel sold or dispensed to consumers in the contiguous United States, on an annual average basis, contains specified volumes of renewable fuel for calendar years 2006-2020.

Amends federal transportation law to require that personal and commercial land and water transportation and shipping vehicles and vessels, as well as large farm equipment manufactured after model year 2010, and capable of operating on either gasoline or diesel fuel, also be capable of operating on a flexible fuel mixture.

Directs the Secretary of Transportation to prescribe regulations requiring a vehicle or vessel manufacturer to include certain consumer information concerning a vehicle's capability of operating on a flexible fuel mixture (alternative biofuels).

Directs the Secretary of Agriculture to: (1) support development of cellulosic feedstock by directing that erosion-preventing, renewable fuel-producing crops be grown on certain arable land in a specified conservation reserve program established under the Food Security Act of 1985; and (2) implement an integrated 10-year research program to improve crop productivity and cost for cellulosic-based ethanol and biodiesel feedstock.

Instructs the Secretary of Energy to implement an eight-year research and development plan to improve significantly processes for converting: (1) cellulosic feedstock into ethanol production; and (2) biodiesel feedstock into biodiesel fuel.