Abstract: A method of firing a melting furnace to which flux or fining additions are made, comprising supplying the burner systems with a fuel mixture containing at least 10% glycerin wherein the glycerin contains sodium chloride (NaCl), potassium chloride (KCl), or a combination thereof. The glycerin can advantageously be raw glycerin, a by-product of biodiesel production. It can be co-fired with natural gas or fuel oil or fired alone in traditional combustion burner systems. Alternatively, the glycerin may be supplied with NaCl and KCl in the same proportion as the flux used in the melting furnace. Significant fuel cost savings and potential flux cost savings may be realized using this method. The method is applicable to furnaces used in the production of aluminum or glass having similar burner systems and utilizing NaCl and/or KCl additions as part of the melting process.