Environmental impact of energy distribution using hydrogen

As an example of estimating the environmental impact of hydrogen energy, we have estimated the emission of CO/sub 2/ from the energy system using hydrogen. For the analyses, electric power and natural gas (city gas) systems are compared. For longer period of utilization the hydrogen system may result in the less emission, while new facility construction may be necessary. Estimation results on the energy transportation using hydrogen pipeline is also summarized, which indicates that for the longer distance the pipeline has the advantage over the electric power system from the view point of CO/sub 2/ emission and also the energy loss if adequate pipes and initial pressures are selected.