by Marianne Lavelle National Geographic Society When President Obama unveiled his long-awaited climate change strategy this week, he never mentioned biofuels. (See “Obama Unveils Climate Strategy.”) But with nearly a third of U.S. greenhouse gas emissions due to burning petroleum for transportation, a key and controversial question is what role plant-based alternatives can play in cutting the nation’s carbon emissions. As part of National Geographic’s Great Energy Challenge initiative, we brought together two dozen experts from industry, academia, and environmental organizations to discuss whether biofuel can be a sustainable part of a cleaner energy future. (See in-depth coverage at Biofuels at a Crossroads, and vote and comment here: The Big Energy Question: Are Biofuels Worth the Investment?“) The forum Wednesday at National Geographic’s Washington, D.C. headquarters was timely, not just because the group convened the day after the President’s long-awaited climate …