CNN: It wasn’t so long ago that biofuels were being heralded as the savior of the planet and a thoroughly green solution to our climate woes. But fair winds have been replaced by persistent storms of criticism. But is it justified? Principal Voices has spoken to three people — an economist, a scientist and an environmental campaigner — at the heart of the biofuels debate. Here, they have their say on biofuels. Have yours at bottom of the page. Keith Wiebe is the service chief in the …