Hydromethane: A bridge towards the hydrogen economy or an unsustainable promise? Carlo Villante*, Antonino Genovese ENEA, Italian Agency for New Technologies, Energy and Environment, Low Impact Vehicles Lab, Casaccia Energy Research Center, V. Anguillarese, 301, 00123 Rome, Italy article info Article history: Received 20 October 2011 Received in revised form 4 March 2012 Accepted 10 March 2012 Available online 22 April 2012 Keywords: Hydromethane H 2 enriched methane mixtures Energy analysis Sustainability abstract Last decade enthusiasm about hydrogen-based economy on FC has partially been lost and spotlight is now back on using pure hydrogen or hydrogen mixtures in ICE. Pure hydrogen use in spark ignition (SI) ICE requires a dedicated engine design to optimize the high speed flame and the high pressure and temperature inside the combustion chamber. But, on the other end, may lead to high exhaust emissions of nitrogen oxides NOx. Moreover, hydrogen fueled vehicles also suffer of a very low mileage due to the very low energy density of the fuel, since hydrogen as a compressed gas at 200 atmospheres and ambient temperature has around 5% of the energy of gasoline of the same volume. All these motivations, together with the now capillary diffusion of natural gas (NG) distribution for residential and transportation purposes (especially in Europe) is making more and more interesting the option of H 2 using as an additive to natural gas: NG powered vehicles, in fact, reached a very high maturity with high reliability and environmental performances. In recent years experimentations were conducted in many laboratories and research centers to verify the positive effects of hydrogen when blended with natural gas. The maturity achieved by H 2 eNG mixtures is also stated by commercialized gas which is available in USA with the registered trademark of Hythane Ò (a mixture of 20% H 2 e80% NG in volume). In this paper the hydro-methane option is fully outlined, a complete energy analysis and environmental sustainability is realized, considering all the main possible options available in mixture production and final use. Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction 1.1. From past to future: mixtures of hydrogen for power generation One of the first applications of H 2 mixtures in thermal cycles was the so-called “water gas”, which is a synthesis gas produced by solid fuels (coal or biomasses) gasification. The process occurs in a stream of air and water vapor used to control flame temperature and reactants concentration to crack the fuel reducing it to its lightest components (mainly H 2 and CO). It is so possible to obtain a syngas which is usable within thermal cycles in reciprocating Internal Combustion Engines (ICE). Its use, during the past years, was made mainly for transportation purposes, in vehicles equipped with an on- board gasifier. Those engines were affected by a reduced efficiency, mainly due to the low heating value of the fuel (less than the half of that of traditionally used fuel for transport uses). Moreover, the imperfect gasification of the fuel caused too frequent maintenance stops for the engine. Other * Corresponding author. Tel.: þ39 (0) 6 30486873; fax: þ39 (0) 6 30484327. E-mail addresses: carlo.villante@enea.it (C. Villante), antonino.genovese@enea.it (A. Genovese). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 11541 e11548 0360-3199/$ e see front matter Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2012.03.066