15 th International Conference on Environmental Science and Technology Rhodes, Greece, 31 August to 2 September 2017 CEST2017_00509 Exergy & Environmental Based Comparison of Hydrogen Production from Natural gas, Carbon and Nuclear energy Nanakı E. 1* , Koroneos C. 1 , Xydıs G. 2 1 University of Western Macedonia, Dept. of Mechanical Engineering, Bakola and Salviera, 50100, Kozani 2 School of Pure and Applied Sciences, Open University of Cyprus, Nicosia, Cyprus *corresponding author: e-mail: evananaki@gmail.com Abstract Hydrogen is an important energy carrier which could play a very significant role in the reduction of emissions of greenhouse gases. The route by which hydrogen is produced is the determining factor for its environmental performance. Hydrogen can be produced through methane reforming, coal gasification or through the electrolysis of water with the use of electricity. However, as these processes involve environmental and energy security concerns, it is of great importance to assess their environmental and energy performance. In this study, the environmental and exergy performance of auto thermal reforming of natural gas, coal gasification and thermochemical water-splitting are evaluated. It is noted that in the thermochemical water-splitting, decomposition reactions take place to produce H2, according to the method of sulphur-iodine. The increased temperature requirements are covered by a nuclear reactor H2-MIR. The calculations reveal that the exergy efficiency of CO2 sequestration reaches 70.3%; whereas the exergy efficiency of carbon gasification process to comes up to 35.8%. Keywords: Exergy Analysis; LCA: Hydrogen production; Carbon Sequestration; Nuclear energy 1. Introduction Concerns about security of energy supply, increased fuel prices, and the impact of emissions of carbon dioxide on global climate change has forced European Union (EU) to search for alternative energy sources. The impact of above factors on the energy sector is going to be intensified in the short and medium term as a result of increased energy demand (European Commission, 2003) and the continuing reliance on fossil fuels. Based on the abovementioned, EU, in order to improve the energy sustainability, has focused on the development of hydrogen energy sources to complement electricity and liquid fuels. It can be used in almost every sector where energy is required—transport, households and services, and in industry. Hydrogen can be produced by using three different energy-supply system classes, namely, fossil fuels (coal, petroleum, natural gas and as yet largely unused supplies such as shale oil, natural gas from geo-pressured locations, etc.), nuclear reactors including fission reactors and breeders, and renewable energy resources (including hydroelectric power, wind power systems, ocean thermal energy conversion systems including biomass production, photovoltaic energy conversion, solar thermal systems, etc.). The successful deployment of the hydrogen-including economy in Europe necessitates the identification of the promising production pathways, both on the large and small scale, that are likely to contribute to the successful penetration of hydrogen in the energy market in the short and medium term. In this context, this study aims to perform a comparative environmental impact study of three different hydrogen production methods. The goal is to provide useful and practical recommendations to policy makers in terms of research and development. Environmental impacts (global warming potential, GWP and acidification potential, AP) as well as exergy efficiencies of three different methods are compared. The method include: the production of hydrogen via natural gas steam reforming, coal gasification, thermochemical water-splitting and the sulphur-iodine method in a nuclear reactor. All three methods are catalytic and they take place at high temperatures. 2. Background : Hydrogen Production Methods under study 2.1. Steam reforming Steam reforming is the most common method to produce hydrogen. In steam reforming, natural gas is first cleaned of impurities, mixed with steam and passed Figure 1. Hydrogen production via natural gas (Spath and Mann, 2001) over an externally heated reactor, carbon monoxide (CO) and hydrogen (H2) are generated. After this step, a catalytic water - gas shift reaction converts the CO and water to hydrogen and carbon dioxide (CO2). The hydrogen gas is then purified. With this technology, it is possible to reach yields higher than 80% in large reformers (Royal Belgian Academy, 2006). The process (Fig.1) takes