NOVELTY - Making a fatty ester involves: processing an alcohol production substrate to produce an alcohol composition comprising an alcohol; providing the alcohol composition, without refining the alcohol composition, to a fatty ester production host; providing a fatty ester production substrate to the fatty ester production host; and processing the fatty ester production substrate in the presence of the alcohol to produce a fatty ester.    USE - For making a fatty ester i.e. ethyl ester useful as biofuel (claimed) e.g. biodiesel.    ADVANTAGE - The method allows for the production of fatty esters from unrefined or relatively impure alcohol sources, which can provide a more economical starting material for fatty ester production than refined or purer forms of alcohol. The method does not require high purity, high concentration, and/or refined alcohol and uses impure and/or unrefined alcohol compositions in the production of fatty esters using a fatty ester production host. In this method one can use an impure alcohol composition to synthesize the fatty ester. This allows to take an alcohol composition directly from its source and to use that alcohol as a substrate for a fatty ester production host to produce a fatty ester. The alcohol is not refined prior to its use in the fatty ester production.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a production system (100) comprising a fatty ester production vessel (164); a fatty ester production host; and a source of impure alcohol in fluid communication with the fatty ester production vessel; and    (2) a fatty ester composition comprising an alcohol production host; and a fatty ester, where the fatty ester is at least 40% by volume of the fatty ester composition.    DESCRIPTION OF DRAWING(S) - The figure shows a production system for producing fatty esters.    Production system (100)    Alcohol production system (102)    Fatty ester production system (104)    Production substrate storage unit (110)    Alcohol production vessel (126)    Production host seed vessel (128)    Fatty ester production vessel (164)