Balancing the energy-water nexus

Energy and water. Water and energy. Both are critical to human development, and both are strongly interrelated.

With few exceptions, water is necessary to generate and distribute energy. In turn, water can’t be collected, purified and transported without energy. A term has even been coined to describe the relationship: the Energy-Water Nexus.

For a company like ours, operating a network of 27 biorefineries with the capacity to annually produce 1.6 billion gallons of ethanol, strategic thinking about water is a necessity. We spend a lot of time thinking about how we use water and where it comes from. More specifically, we focus on conserving water by using less and drawing it from alternative sources.

An ethanol biorefinery needs water primarily for three things: to create the aqueous environment necessary for fermentation, to generate steam in the boilers and to subsequently cool the process systems by removing heat. The perception exists that it takes a lot of water to make ethanol, and at one time that was true. In 1988, our first year of operation, our biorefinery required 18 gallons of water for every gallon of ethanol produced.

But at that time, the industry was in its infancy, technology was unreliable and virtually no ethanol plants were operating profitably. Significant gains had been made by 2009; so that same gallon of ethanol produced in one of our facilities required just over three gallons of water.

How did we do it? How were we able to decrease our water use by more than 80 percent? It was through a sustained focus on both the efficiency of the entire ethanol production process and the specific issues related to water use.

Efficiency improvements in the overall process have contributed significantly to the decrease in water use. In many cases, sustainability can involve trade-offs. But in the case of the Energy-Water Nexus, a decrease in energy use often leads to a corresponding decrease in water use and vice versa.