GAO Report on 21st Century Energy Demand

From a GAO report on energy demand in the 21st century (from the abstract):

[A]ll of the major fuel sources--traditional and renewable--face environmental, economic, or other constraints or trade-offs in meeting projected demand. Consequently, all energy sources will be important in meeting expected consumer demand in the next 20 years and beyond.

Thanks to Lynn Kiesling for the link.