Lignin from hemp could be a possible bitumen replacement: https://gizmodo.com/a-compound-from-plants-could-replace-bitumen-to-make-ro-1693050702 https://gizmod

Lignin from hemp could be a possible bitumen replacement: https://gizmodo.com/a-compound-from-plants-could-replace-bitumen-to-make-ro-1693050702 https://gizmodo.com/a-compound-from-plants-could-replace-bit... Looks like hemp is 5-30% lignin depending on the type, with female hemp having roughly double the lignin content by dry weight: https://www.sciencedirect.com/science/article/pii/S2238785414000982 https://www.sciencedirect.com/science/article/pii/S223878541... https://www.hempbasics.com/hhusb/hh3fiber.htm https://www.hempbasics.com/hhusb/hh3fiber.htm Also algae oil can be converted to a bitumen-like tar with roughly 55% efficiency, so if we assume the best algae is 50% oil by weight then we end up with about 25% tar by weight (I can't find confirmation of this, so they might mean 55% tar from algae directly): http://news.algaeworld.org/2015/04/algae-bitumen-could-soon-pave-roads/ http://news.algaeworld.org/2015/04/algae-bitumen-could-soon-... Perhaps these could be combined with recycled plastic to make an asphalt derived purely from biomass and recycled materials.