Just the Gulf of Mexico has 384 million acres. Microbes containing oil probably float, and there's plenty of free farm fertilizer runoff. The final replacement for petroleum will probably involve the open ocean because that's where all the energy in petroleum originally came from.
Won't ever happen though. Detroit City is too addicted to government handouts, like the Province of Quebec, here in Canada. The powers that be that run such places would lose their power base, if their voters were freed of welfare. Kinda like Washington, District Cesspool!