The realization of dwindling fossil fuel supplies and their adverse environmental impacts has accelerated research and development activities in the domain of renewable energy sources and technologies. Global energy demand is expected to rise during the next few decades, and the majority of today's energy is based on fossil fuels. Alternative energy sources and technologies can play a vital role in lowering or eliminating our reliance on fossil fuels. However, such a transition will require a large investment and will not be reversible. The benefits of hydrogen and other liquid fuels as transportation fuels are not marginal, but the real urgency in greenhouse gas reductions and fossil fuel replacement should not be translated into an energy infrastructure based on unsustainable sources in the long run. It is wise to examine each option thoroughly and objectively now and discard those with little potential so our focus and effort may be placed elsewhere. (Contains 7 figures and 1 table.)