This chapter discusses hydrogen-methane blends for use in the transportation industry. The use of fossil fuels in hydrogen production may limit the advantages of this technology. However, a more sustainable approach is being developed in the use of renewable sources to supply energy for electrolysis. An energetic and environmental assessment of hydro-methane is necessary to determine its sustainability, and the information collected must be used to drive technological choices. © 2014 Woodhead Publishing Limited All rights reserved.