A laboratory process to ferment highly concentrated mash, with greater than 30% solids, has been developed [38]. Very-high-gravity (VHG) fermentations produce 21 to 23% ethanol under optimal fermentation conditions. The VHG process requires a mash with high sugar concentration and low viscosity, which can be achieved by adding enzymes (e. g., proteases, glucanases, and amylases) or by double mashing, in which the solids are removed from an initial mash, and the liquids are used to prepare the second (VHG) extract. VHG fermentations use less water than conventional fermentations. Energy costs also decrease because there is less volume to cool for fermentation and then distill.