stephen judkinsProfoundly depressing to see the argument that we need to keep running diesel buses, with their significant carbon emissions (40 passenger-mpg in Portland) and carcinogenic diesel pollutants spewed into dense neighborhoods, because the alternative is a 20% higher capital spend (or decades-long project to put up catenaries)
😀🚲@stephenjudkins how are the pollutants from renewable diesel vs petro? In any case we're probably going to be the last major us city to figure out trolleybuses.
@stephenjudkins did you mean catenaries?
@enobacon yes autocorrect
@enobacon I assume they're probably equally bad, given how similar the two fuels are chemically.
And I doubt many more trolley buses are going in anywhere, almost everywhere is going to go straight to batteries
@stephenjudkins I have my doubts about wireless electric transit and freight but show me a bus full of batteries every five minutes and how we charge them I guess
@stephenjudkins I can't seem to find much about renewable diesel that doesn't smell like soybean lobby but I can smell petro diesel exhaust quite acutely and R99 is different, without the nox of biodiesel. If the carcinogens are produced in imperfect combustion vs impurities in the fossil fuel, IDK. Maybe slightly better for that it combusts better at least.
I guess it's a question of whether it produces more, and which, particulates. I think biodiesel has less need for dpf regen, so is that ester vs paraffin or is it impurities that don't burn and aren't in the bio source feedstock?
@stephenjudkins https://ntp.niehs.nih.gov/ntp/roc/content/profiles/dieselexhaustparticulates.pdf
@stephenjudkins https://ntp.niehs.nih.gov/ntp/roc/content/profiles/dieselexhaustparticulates.pdf
Benjamin Ross@enobacon @stephenjudkins Biological lipids tend to have oxygens, where diesel is more straight hydrocarbon. Both generate polycyclic aromatics as products of incomplete combustion - there's a literature about PAHs formed by grilling meat. I doubt there's a simple answer about which generates more.
@BenRossTransit I'm wondering about renewable diesel though, which is the same feedstock as biodiesel but cooked down in the same refinery equipment as petrodiesel, which removes oxygen. Petrodiesel gets 5% bio lubricity additive (used to be sulphur or something related pre ulsd) but R doesn't? Anecdotally so far, it smokes less. Better combustion seems likely to produce lower particulate output, but I would like to see studies. Bio sources locally seem to have switched to R.
@stephenjudkins
@stephenjudkins
Number One Shoup Fan@stephenjudkins I'd put it that right now no city wants to go first with battery busses. The tech just doesn't seem quite there. Seems like it would be worth it for the feds to step in and fund some larger project to get the kinks out.
yarrriv@OneShoup @stephenjudkins I think phrasing it as just a matter of paying 20% more is disingenuous, there are range issues and obviously you need capital investment in charging stations. For places with cold winters in particular I think it's not there yet, though for Portland it might work
@OneShoup @stephenjudkins and then on particulate emissions, if we removed every single diesel bus would air quality in Portland (or anywhere) change significantly? This will be more convincing if we had car-free cities, or once the majority of private cars on the road are electric. But that's still a decade or two away I think