At the end of last year, NRDC joined the Center for Biological Diversity, Earthjustice, Friends of the Earth and Oceana in petitioning EPA to address heat-trapping emissions from aircraft. While its contribution to global warming pollution is small relative to surface transportation vehicles (cars, trucks and heavy trucks), it has an important role given interest among some in the industry -- and even moreso in the Air Force -- in dirtier alternatives to jet fuel from conventional oil.

Thankfully, a daring entrepreneur with a lot of pull is heading in the right direction. Lord Branson plans to fly a plane from London to Amsterdam powered in part by biofuel.

One might ask: What kind of biofuel, and where will it come from? Virgin Atlantic and Boeing, partners in the initiative, aren't saying. This is fueling speculation about a particularly intriguing option: Biofuel using algae as a feedstock, which has been written about before among other places in the pages of In Business magazine.

To learn more, read this great piece by Bruce Falconer for Mother Jones online, "Virgin Airlines: Powered by Pond Scum?"