It might be worth the trouble for some, who have access to used cooking oils.
20 year ago I drove Powerstroke 7.3 and Mercedes diesel sedan with mechanical injection pump. They were good candidates for veggie, so I researched the subject.
Found UK Mercedes owner who drove on straight cooking oil and installed special fuel heating module, using standard Glow Plugs for heating. That worked for him, when combined with cardboard covering his radiator on cold day. Shall I said that cardboard did not make good impression?
Other member set some old water heaters on his property to make bio diesel. That was stinky business and don't do it if you have neighbor closer than 1/2 mile away.
At the time I bought few barrels of 100% biodiesel and run it on those vehicles. Power loss was pretty noticeable, but smell of French Fries was actually nice.
But the source of bio dried out and since most of my fill-ups at the time were far away from home, I figured it out not worth the trouble.
YMMV