Introduction: A sustainable energy future with a stable global climate is central to the present worldwide debate on climate change due to the emissions of carbon dioxide (CO2), which is the main greenhouse gas (GHG) from human activities. The grand challenges faced by mankind in the coming years are the creation of a sustainable energy system caused by the depletion of fossil fuel resources (or their availability at a reasonable cost) due to the rapid growth of the world population and the related strong increase in energy demand and the negative impacts on the global climate due to large uncontrolled. | Hydrogen Economy M Conte Casaccia Research Center Rome Italy 2009 Elsevier . All rights reserved. Introduction A sustainable energy future with a stable global climate is central to the present worldwide debate on climate change due to the emissions of carbon dioxide CO2 which is the main greenhouse gas GHG from human activities. The grand challenges faced by mankind in the coming years are the creation of a sustainable energy system caused by the depletion of fossil fuel resources or their availability at a reasonable cost due to the rapid growth of the world population and the related strong increase in energy demand and the negative impacts on the global climate due to large uncontrolled GHG emissions from using conventional fossil fuels. According to the International Energy Agency IEA Energy Outlook the world s primary energy demand is likely to double in the next 50 years with fossil fuels still having a large share - up to 80 depending on the implementations of specific climate change policies with an increasing contribution from coal coupled with decarbonization processes due to its lower price. The depletion of fossil fuels will continue despite higher efficiencies in usage being reached in the coming years. Energy consumption rise will depend on societal and economic changes in the world together with a significant growth of the global population which is expected to increase from today s billion to peak at billion in 2050. Independent of the effective time frame for reaching peak reserves and the shortages in the availability of fossil fuels in the future key issues are related to security in supply from producing countries and affordable costs. Carbon dioxide is essential for life on our planet. Animals plants volcanoes oceans and forests control in a delicate system of complex equilibrium the carbon dioxide concentration in the atmosphere too low or too high values can lead to global climate changes and then to a cooling or warming of the .
