Renewable Fuel Pipelines Act of 2008 - Amends the Energy Policy Act of 2005 to allow federally-guaranteed loans for renewable fuel pipeline construction without regard to whether an appropriation for the cost has been made. Includes ethanol and biodiesel as renewable fuel.
Allows a maximum guarantee by the Secretary of Energy of 90% of the project cost and more than one guarantee for a project (as long as the total guaranteed amount does not exceed 90%).
Sets forth factors to be considered in guarantee determinations, including volume and quality of fuel, size of markets served, experience of the entity working with renewable fuel, and associated storage, production, and terminal facilities.
Expresses the sense of Congress concerning appropriations for such guarantees.
Directs the Secretary to publish a final rule for carrying out the loan guarantee program (or modify existing applicable rules and regulations in accordance with this Act).