The problem with the premise of the original question (biodiesel vs hybrid emissions) is that there's no common standard in the US for what constitutes "biodiesel" in the first place (notwithstanding the propaganda from the commercial biodiesel industry); the German car companies who probably have the most experience with passenger car diesel engines, like VW, won't warranty a car in North America with a more than 5% biodiesel blend. Period. And in Europe, there are just now being agreed upon manufacturing standards for what is called "biodiesel".

So, not knowing what exactly constitutes biodiesel fuel, it's impossible to make accurate predictions as to how the new Ultra Low Sulfur Diesel emission-equipped cars (model year 2009 VW, for instance) will perform when using non-standard fuel. From what I've been reading, the new emission systems are even less tolerant of biodiesel than were the Low Sulfur Diesel equipped cars previous.

And all this talk of comparing biodiesel cars with hybrids is nonsense anyways; Joe Sixpack or Soccermom Sally aren't going to mess with gelled fuel filters in the cold months, and having to worry about blend ratios when the temperature begins to fall. They just want a vehicle that will take them from point A to point B with minimal hassle. Until biodiesel is manufactured to international agreed to standards, and cars are specifically engineered for their use (which the new ULSD emissions-equipped cars ARE NOT), it's just pie in the sky.

BTW, VW MY 2008 diesel passenger cars introduction to the US are being delayed, due to problems during long-term emissions testing. Latest word is fall of 2008, which is MY2009.

~Joe

1998 VW Jetti TDI owner