If you don't grow your own but would like to eat organic produce then there is a growing number of ecological farms that sell to the public.

In Tortosa there is La Sort, huge selection of own grown produce plus produce brought from other suppliers, in Xerta there is at least one just on the edge of the village, in L'Aldea there is another (not sure exactly where). I was recently told about another on the outskirts of Roquetes, heading towards Els Reguers.

I believe there are some that deliver.