Actually, if you look at the results of the tests conducted by the people who did them, you will see that they were not done for statistical accuracy, or for any kind of consistency. Additionally, the NOx increase was within one standard deviation, leading to beleave that it could easily be an anomaly.
There have been numerous reports that say that biodiesel does NOT increase NOx emissions versus ULSD
Also a good read:
http://www.nwventurevoice.com/archives/2005/05/nrel_says_biodi.html
We should also not that, in every other type of emissions test, Biodiesel resulted in a great decrease of every other contaminate tested by CARB states.
I gladly run biodiesel in my TDI, and feel good for it.