Risk assessment by means of Bayesian networks: A comparative study of compressed and liquefied H 2 transportation and tank station risks Hans J. Pasman*, William J. Rogers Mary Kay O’Connor Process Safety Center, Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA article info Article history: Received 14 January 2012 Accepted 7 April 2012 Available online 31 May 2012 Keywords: Risk assessment Bayesian networks Decision making Land use planning abstract Rational decision making in land use planning and licensing of H 2 infrastructure sur- rounded by other industrial activities and by population should take account of individual and societal risks. QRA software packages produce a risk matrix of potential consequences versus event probabilities without indicating uncertainty, and results are therefore shrouded in ambiguity. Due to the ‘black-box’ effect of a package, the calculations also lack transparency. Bayesian Belief Network (BBN) software modeling cause-consequence chains allow easy inspection of intermediate results and sensitivity tracking, and it can take account of data distributions instead of point values. For support of decision making, risk analysts should in addition determine the utilities of decision alternatives. Utilities describe desirability of benefits on a single scale. Rationally weighing risks versus benefits results in more transparent and defendable decisions. Example risk analyses of two types of refueling stations and three hydrogen supply transportation types applying BBNs are worked out. Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction New technology involving hazardous materials comes with certain risks, especially when it is introduced on a large scale and becomes widely distributed to involve many people. In such circumstances, just as a consequence of large numbers, incidents and accidents will be unavoidable despite inherent safety measures built into the system. One accident with fatalities and spectacular effects dramatized in the media will stir up public concern and generate process ‘viscosity’ in land use planning and licensing processes resulting in delays. Risks should therefore be assessed not only in planning stages, design, and construction, but even more in operation and use. Hydrogen is a very clean and useful replacement of common fuels such as gasoline and can be applied as a fuel in (micro-) Combined Heat and Power (CHP) systems for dwell- ings and offices. Its use could therefore become widespread, certainly as a means to counter the climate change problem. In most applications, it will have to be stored in a compressed gaseous state, and due to its size as a molecule, it will be leak prone. Alternatives are liquefied (boiling temperature 20 K) and absorbed, e.g., as a hydride. When mixed with air, its properties are known from a hazard point of view: high reactivity, low ignition energy, and wide explosive limits. Explosions in the open and fire cannot be excluded. Both the USA EPA RMP rule [1] and the EU Commission Seveso * Corresponding author. Tel. þ1 979 845 3489. E-mail address: hjpasman@gmail.com (H.J. Pasman). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 17415 e17425 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.2012.04.051