I don’t really know how much it would cost today to build a reactor. If you’re technical, you can build a reactor out of scrap. If you can weld, you can make a better one. I think the hardest part is just sourcing reliable used fryer oil from restaurants.

Unfortunately, all the best resources online are dead now and the remaining ones are bad. How the hell is Journey to Forever still up, but Biodiesel.infopop.cc is down? You can probably still get all the info from Waybackmachine.