Different Options for Producing Hydrogen with Reduced CO2 Emission

CHAPTER 1 INTRODUCTION 93 Hydrogen production worldwide is currently totalling 500·10 Stm/year. As shown in table 1.1, the main sources for hydrogen production are fossil fuels, with natural gas covering the 48% of the total. Hydrogen is currently not used as a fuel, but is generally used in chemical synthesis processes (methanol, ammonia) and in oil refineries (table 1.2). However, due to the increasing concerns for the anthropogenic greenhouse effect, interest is growing in the use hydrogen as a future energy carrier and in technologies to mitigate CO emissions. 2 Table 1.1: Hydrogen production worldwide (2002) [1] 93 Source 10 Nm/year % Natural Gas 240 48 Oil 150 30 Coal 90 18 Electrolysis 20 4 Total 500 100 Table 1.2: Hydrogen utilization [2] 93 H utilization 10 Nm/year % 2 Ammonia production 254 51 Refineries (H produced in dedicated plants) 98 2 36 Refineries (H obtained as a by-product) 83 2 Methanol production 37.5 7.5 Others (chemical, electronics, steel, food, glass…) 27.5 5.5 The anthropogenic greenhouse effect, which is considered the main reasons for climate change, is ascribed to the increasing CO concentration in atmosphere (see 2 figures 1.1 and 1.2), due to the combustion of fossil fuels. Various strategies and technologies have been proposed for reducing CO emissions from power generation 2 plants: (i) energy saving; (ii) use of renewable resources; (iii) improvement of plant thermal efficiency; (iv) use of fuels with a low carbon content; (v) carbon capture and sequestration. Several studies have analyzed the impact and the effectiveness of these strategies on the reduction of greenhouse effect. However, due to the increasing world population, energy consumption and use of fossil fuels, most scenarios suggest that strategies (i)-(iv) will not be able to achieve the necessary reduction of CO emissions, without carbon capture and sequestration. 2 1