The present application generally relates to the introduction of a renewable fuel oil as a feedstock into refinery systems or field upgrading equipment. For example, the present application is directed to methods of introducing a liquid thermally produced from biomass into a petroleum conversion unit; for example, a refinery fluid catalytic cracker (FCC), a coker, a field upgrader system, a hydrocracker, and/or hydrotreating unit; for co-processing with petroleum fractions, petroleum fraction reactants, and/or petroleum fraction feedstocks and the products, e.g., fuels, and uses and value of the products resulting therefrom.