We “know” that petroleum as a fuel source is running out. Not as fast as we once thought- only because as the price rises, sites and sources that were out of reach (economically) become more feasible. Think Athabascan tar sands, coal to gas, fracking (water fracturing of structures to release natural gas). But, we still need alternative sources, not only as a national security issue, but to reduce our carbon footprint and maintain/improve our air quality.