|Fig. 1: Glenmorangie Distillery. (Source: Wikimedia Commons).|
Distillery wastewater is a byproduct of the industrial production of alcohol. As you might have guessed, distillery wastewater is produced in distilleries, like the Glenmorangie Distillery seen in Fig. 1. Surprisingly, it is one of the most polluted waste products to dispose because of the low pH, high temperature, dark brown color, high ash content and high percentage of dissolved organic and inorganic matter.  Not only is distillery wastewater quite potent, but it is also quite plentiful. For every liter of alcohol produced, about 15 liters of spent wash is released.  Keeping in mind the vast quantity of alcohol that is consumed every year, this is an incredible amount of waste.
From the description of distillery wastewater above, it is clear that this substance has serious environmental implications. However, surprising enough, it also has implications for fossil fuels. Technology has emerged that allows for the simultaneous treatment of wastewater and production of electricity. Researchers have combined two systems, the microbial fuel cell and the anaerobic fluidized bed, resulting in a COD removal efficiency from 80 to 90%, and a maximum power density of 124.03 mW/m2 under an external resistance of 120 Ω and a variety of system operational settings.  In layman's terms, this combination has resulted in an efficient water treatment and electricity producing device. On one hand, this technology kills two birds with one stone: it substantially reduces the amount of pollution literally pouring out of thousands of distilleries around the world, while at the same time producing electricity without the use of traditional fossil fuels, providing a cleaner and eco-friendly source of power. On the other hand, when breaking down the actual amount of power produced per liter of spent wash, the number is quite small. Assuming a COD of 100 g/L, every kg or wastewater produced by distilleries contains about 0.1 kg of oxidizable dry waste.  For every kg of dry waste, the energy extractable by any means is less than about 2.2 × 107 joules. In 2012, the United States produced 1.1085 × 1010 gallons of distilled spirits, or 
For every liter of alcohol produced, about 15 liters of wastewater is produced.  Each Liter has a mass of 1 kg. The energy potential from this waste is thus
The price and efficiency of extracting energy from this waste aside, the US energy need (around 1020 joules) is 72 times greater. Once you take into account the cost of materials involved in the process (materials such as significant amounts of platinum), this does not appear to be a viable large-scale power generator, or the United States would have already seen a booming distillery wastewater power industry.
Despite its shortcomings, this technology serves a third purpose. It reminds us that positives can always be made out of negatives, a message that is truly important to remember when pursuing alternative methods of power generation in a world crippled by emissions.
© Jack Dreyer. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 Y. Kharayat, "Distillery Wastewater: Bioremediation Approaches," J. Integr. Environ. Sci. 9, 69 (2011).
 J. Huang et al., "Electricity Generation During Wastewater Treatment: An Approach Using an AFB-MFC For Alcohol Distillery Wastewater," Desalination 276, 373 (2011).
 "Statistical Report - Distilled Spirit," U.S. Department of the Treasury, Alcohol and Tobacco Tax and Trade Bureau, TTB S 5110-12-2012, April 2013.