The energy short-falls of the 1970's made clear both individual and national vulnerability when reliance is on a single energy source such as petroleum. Further, the situation was a sharp reminder that fossil fuels are finite and that their supplies will become limiting. Whether short supplies are for political, economical, or geological reasons, they signal the need to plan for a future with diverse options so.that needs can be met without disruptive consequences when supplies of one source become limiting. Conservation plays a major role in any strategy; however, it should be recognized that such steps can only "buy time" by extending the supply - not create new energy supplies. Proven petroleum reserves in the United States currently are stated to be equivalent to only 8~ years consumption at current rates assuming no imports or additional petroleum discoveries. Another important strategy is to develop biomass, solar and other alternative energy supplies and integrate their use into contemporary society. A fundamental difference between fossil fuels and biomass involves the concept of stock versus flow resources. For example, the amount of crude oil is basically a fixed or stock level which is being rapidly mined.
