Oh, there's no way to make it carbon neutral in and of itself, that's just corporate / marketing bullshit. Replacing oil with biofuel doesn't get away from using carbon (and you've got all the industry involved in agriculture to go with it, plus a new set of refining processes), because carbon is at the core of polymers. What it does do is stop moving carbon from ancient sequestration back into the current atmosphere, which is something of an improvement, if already far too late.