Biogas Investment Tax Credit Act of 2013 - Amends the Internal Revenue Code to allow: (1) an energy tax credit through 2018 for investment in qualified biogas property, and (2) financing of qualified biogas property with new clean renewable energy bonds. Defines "qualified biogas property" as property comprising a system which uses anaerobic digesters or other processes to convert biomas into a gas which consists of not less than 52% methane and which captures such gas for use as a fuel.
Directs the Secretary of the Treasury to enter into an agreement with the National Renewable Energy Laboratory to undertake a study of biogas and to submit a report to Congress on such study.