How Green Are Billboard's Greenest Musicians?

I love the Roots, but I wonder how green some of Billboard's greenest musicians really are, especially the ones being honored for using biofuels. [Click on the image for a larger version of the cartoon. The text reads: "The day after Earth Day, Billboard named the ten greenest musicians, and I was excited that the Roots made the list because they speak out about nonviolence and vegetarianism, and I'm not a Radiohead fan, but I'm glad they were on the list too because it was pretty radical to make a downloadable-only album and they also pretty much refuse to travel, but a lot of the musicians on the list just do things like carbon offsetting and using biodiesel in their tour buses, which reminds me of that Live Earth concert last year when thousands of people traveled thousands of miles and made a negative environmental impact so they could tell people not to make a negative environmental impact, and while I understand the motive for Willie Nelson's biodiesel, there are food riots going on because we might not be able to use our crops to keep all these cars and trucks going, so we should probably try to be more like my gerbil because the only wheel he keeps rolling is the one he powers himself."]