Method for producing renewable fuel

A process for preparing hydrocarbons from an oxygenated hydrocarbon feedstock, such as animal fat, having a high nitrogen impurity is described. Hydrotreatment of the oxygenated feedstock occurs in a first hydrotreating bed arranged downstream of a polishing bed. A gaseous phase is removed and the liquid hydrotreated phase is fed to the polishing bed arranged upstream of the first hydrotreating bed together with fresh hydrogen. The process effectively removes nitrogen impurities from the resultant hydrocarbon product causing an improved cloud point after isomerisation, and the arrangement makes efficient use of fresh hydrogen for polishing, providing a polished hydrocarbon product rich in dissolved hydrogen. Part of the product can be used as hydrocarbon diluent in the downstream hydrotreating bed, and/or withdrawn between the polishing and hydrotreating bed and isomerised in an isomerisation reactor.