Here's yet another complicated and confusing question about the transition to a post-greenhouse gas world: Is what's billed as low-carbon gasoline good or bad for the environment?

That's the question lawmakers in several Democratic-led states are asking themselves, and no easy answers are appearing.

New Mexico, New York, and Minnesota, to name a few, have debated new standards that would encourage the adoption of more climate-friendly auto fuels, either through blending with ethanol or with another type of biofuel. But in all of these states, these measures failed amid opposition from environmentalists, who say a new fuel standard would simply delay the abandonment of fossil fuels altogether.

On today's Parts Per Billion, our biweekly environmental law podcast, we hear from reporter Zach Bright about why low-carbon fuel standards are struggling to gain traction at the state level, despite support from high-level Democrats. Bright also talks about the states that have managed to adopt their own standard, and how they did it.

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