TOWERING CHALLENGE: What needs to be done if we are to reduce our dependence on fossil fuels?
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Climate change. Energy independence. Air pollution. There are countless arguments for moving beyond fossil fuels for our energy needs. Unfortunately, there are just as many hurdles that must be cleared before we can feasibly count on other sources to supplant oil, coal and natural gas, which currently provide the lion's share of U.S. electricity generation and transportation fuels.

To illuminate the scope of the task, Scientific American recently surveyed a number of top executives at firms engaged in developing and implementing energy technologies—solar, wind, nuclear, geothermal, biofuels—that could reduce our global dependence on fossil fuels.

The execs were asked to describe some of the challenges facing their industries. In a time of worldwide economic turmoil, many of those challenges are financial, but others are technical, infrastructural and even cultural. Taken together, the surveys provide a blueprint of steps companies, policymakers and consumers must take to wean the U.S. and the world off of fossil fuels or at least limit their use.

This week and the next, we will present the energy executives' surveys in their entirety. Check back as we roll out their responses as follows:

Monday, April 20:
Eric McAfee, chairman and CEO, AE Biofuels
Gerald Grandey, president and CEO, Cameco Corporation (uranium production)

Tuesday, April 21:
Barry Cinnamon, CEO, Akeena Solar
Aris Candris, president and CEO, Westinghouse Electric Company (nuclear)

Wednesday, April 22:
Alan Hanson, executive vice president, AREVA (nuclear)
Harrison Dillon, co-founder, president and chief technology officer, Solazyme (microbial fuel production)

Thursday, April 23:
David Crane, president and CEO, NRG Energy (nuclear)
Leon Steinberg, CEO, National Wind

Friday, April 24:
John Melo, CEO, Amyris Biotechnologies (renewable fuels)
Daniel Kunz, president and CEO, U.S. Geothermal

Monday, April 27:
John McDonald, CEO, ExRo (wind)
Sanjay Pingle, president, Terasol Energy (biofuels)

Tuesday, April 28:
William Johnson, president, chairman and CEO, Progress Energy (nuclear)
David Mills, founder and chief scientific officer, Ausra (solar thermal)

Wednesday, April 29:
Bob Gates, senior vice president for commercial operations, Clipper Windpower
David Ratcliffe, president, chairman and CEO, Southern Company (nuclear)

Thursday, April 30:
Lucien Bronicki, chairman and chief technology officer, Ormat Technologies (geothermal and recovered energy)