Given the very small amounts of grease used in a bicycle, I think that the environmental friendliness of the grease (however defined) is of such minute impact that there is little point in worrying about it. It's the "consumable" petroleum products that are more worth worrying about (i.e., things burnt as fuel, or even lubricants that are renewed/changed much more frequently). I'm not trying to say that it's not worth worrying about at all - just that other things have much bigger potential impact. Even chain lube choice would be of much bigger impact, given the higher frequency of lubing a chain, versus re-packing BB's and wheel hubs. Just my $0.02...