First we need to find wheat seeds
With a little luck, these can be found in the first village.
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Now we need to build a workbench in the inventory crafting menu.

Next, we craft a planter box. In my case, I went straight for the large planter box.

After we have set up the planter box we can pick up the wheat seeds and plant them with a left click.
And now we have to wait until they are fully grown.

Now we can craft an Alembic in the workbench
and place these.
Now we can produce ethanol

Now we can simply go to any vehicle and refuel it

You can refill the empty ethanol canister at a tanker truck.
(Crafted empty canisters cannot be refilled at a tanker truck.)
There are currently five tanker trucks on the map. Here are two examples.