Never be misled: at core, the Sierra Clubbies and other green weenies are core are opposed to all human economic activity, and whenever they support one energy mandate (e.g., ethanol fuels, wind, solar, etc.) it's because they think that energy is totally economically non-viable, and will thus simply result in people not driving, not using electricity, etc.
They'll never be happy until we all live in mud huts and ride bicycles for transportation.
In this they're like the so-called automotive safety and emissions mavens, whose real interest is not in cleaner, safer cars but in setting targets so unrealistically high that the cost of meeting them results in unaffordable cars, and we're back to the bicycles thing.
OK, I need to check grammar before I post a little more often...