Abstract

Based on a Danish study, the potentials and limitations for energy conservation and reduction of CO2-emissions by means of fuel cycle efficiency improvements and introduction of renewable fuels in the transport sector are studied. Different energy cycles (based on e.g. electric propulsion, hydrogen, biofuels) are compared. Also, the scope for resolving transport sector problems by means of renewable fuels and energy cycle efficiency improvements is assessed, especially with a view to the time perspective. Fuels based on both fossil and renewable energy are evaluated. The main aspects covered are fuel use, energy cycle emissions (particularly CO2) and land requirements. For renewable fuels, the land requirement - which can be considerable - is a particularly important factor, especially in densely populated countries.

It is concluded that, among the energy carriers for renewable fuels, electric and hydrogen propulsion (including fuel cells) have much higher energy cycle efficiencies than biofuels and other biomass derived fuels, thus requiring less resource inputs to met given fuel demands (especially land use). Comparing electric and hydrogen, it is not possible to choose one single "best candidate" since they perform supplementary roles in a strategy for sustainable transport. Electric vehicles generally represent the most efficient energy cycle but they are lim-ited to short driving ranges, at least when based the present battery technology. If longer ranges are required, hybrid and hydrogen propulsion can be options. Technological development (batteries, hydrogen storage and fuel cells) can influence these priorities. Moreover, technological measures should be regarded as a supplement to, and not substitute for, other transport planning measures. In particular, the issue of the transport demand is important, especially in the short term where most of the technological improvement measures are found to have limited effect.

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Panels of

Panel 1: Policy (incentives, normative measures, policy mixes to achive CO_2 reduction)

Panel 2: Technologies and Products (innovation, marketing, market transformation)

Panel 4: Environmental Perspective (externalities and life cycle approaches, local and global impacts and incentatives)

Panel 3: Dynamics of Consumption (social and cultural perspectives, actors and their interactions)

Panel 5: Land use,Transportation and infrastructure (urban and regional planning, approaches to change in well entrenched systems)