Not really diesel related but an article about greenwashing. The relevant part is quoted below
Yet errors have plagued efforts to green the planet. On the personal front, although recycling is better than tossing aluminum, plastic, glass and paper in the trash, the order of priority is "reduce, reuse, recycle." Instead of recycling two-quart juice bottles, we should have been telling people to buy 12-ounce concentrates and refill that bottle 100 times before putting it in the blue bin. Even hybrid electric cars aren't a clear plus. If your outlet gets its juice from the standard U.S. electricity mix (half of which is generated by burning coal), hybrid electrics emit half the greenhouse gases as standard gasoline cars. But if your utility burns dirty coal inefficiently, hybrid electrics are worse. If you plug in at night, when most people do, you'll also be using more coal-generated electricity. Perhaps the greatest folly, in time lost and dollars wasted, has been the push for ethanol to replace gasoline. In the United States, almost all ethanol comes from corn. When you tote up the carbon emissions caused by clearing land to grow corn, fertilizing it and transporting it, corn ethanol leaves twice the carbon footprint as gasoline.
The greenwashing doesn't end there. Only half of all hybrid vehicles on the U.S. market are more fuel-efficient than their non-hybrid versions, researchers at the Union of Concerned Scientists find: some models pair a big gas-guzzling engine with hybrid technology in a way that enhances only performance, not fuel economy, explains UCS's David Friedman. "Don't assume that because something's a hybrid it's better for the environment," he says (though the Prius is). The Web site fueleconomy.gov sorts out the true greens from the impostors.