[Campion]

but once you use anything higher than B20 ( 20% biodiesel) I understand that the emissions are much higher than a regular diesel engine.

No, they're lower. But fuel mileage suffers a bit, and some engines have problems with rubber seals swelling and the like.

[bamaintx]

i belive if you go and check many of the large diesel manufacture ( big diesel engines, 8 liters and larger) like the one that is the opposite of dog you will see that they recommend not to use more than B5 in their engines.
This is due to a few reason, power, performace, longevity, maintenance, fuel economy, and emission all suffer.