Biofuels don't scale very well. You can indeed produce some "for free" from waste, but once you start planting areas solely for producing biomass to turn into biofuels, you're environmentally much better off to leave the land to nature and put up some PV or wind turbines there.

But yes, a tiny sliver of fuel demand can be satisfied from plants. You're right about that. I'm less convinced that you're better off burning the fuel in an ICE than turning it into electricity in a large power plant and running an EV. Large generators are more efficient than small ones. If you manage to do something useful with the waste heat of your power plant (e.g. use it for district heating), there is no way a small ICE can compete, even if you take into account transmission and charging losses.