It just seems so grossly unfair that most of the current ways to purify water for human consumption are incredibly energy-inefficient.
I am thinking about this as I read a white paper from Dow Water & Process Solutions called "A Different Look at Water, Part 1: Water for Cities and the Water-Energy Nexus." Obviously, this is not a disinterested white paper (then again, what water paper IS disinterested). But there is a sobering statistic within that I would like to share: According to Dow, it takes 140 gallons of water to produce one megawatt-hour of power using natural gas. The good news is that it only takes 30 gallons with photovoltaic solar technology.
This mathematical challenge is the so-called water-energy nexus, and it will be one of the biggest challenges that we all face as more of the world's population migrates to urban areas. As the human population requires more clean water, it will take more energy to produce it. So, for all our focus on cutting power usage, we'll be at square one again.
While many of us tend to think of the water-energy nexus as a developing world problem, the fact is that established cities in the United States (and Europe for that matter) are just as vulnerable.
A report in October 2010 by Ceres, 24/7 Wall St. and the National Resources Defense Council figures that 10 of America's biggest cities face severe water shortages in the future. Those cities (based on population growth, average annual precipitation and anticipated water consumption) are:
- Los Angeles
- New York
- Fort Worth, Texas
- San Diego
- Las Vegas
- Tucson, Arizona
So what do we do about this? Technology will be one big answer, of course. Last week in my GreenTech Pastures blog for ZDNet, I wrote about three green technology companies that are working on innovations that will make better use of urban wastewater, by either creating energy from it or by purifying it for reuse. Those three companies juts received some funding as part of the 2010 Water-Energy Nexus Prize. They are:
- Hydrovolts, which is experimenting with turbines that create energy from water currents
- Blackgold Biofuels and FOGbusters, both of which are focused on taking fat, oils and grease out of wastewater to make it suitable for other uses
There are other big companies applying innovative muscle to the problem, notably companies like Dow and ITT. Generally speaking, the Dow white paper offers some tips for municipal planners to make better decisions that ride the line of good water and energy policy. Here are some of the issues and technologies that were are all like to hear a lot more about in the coming years, as people wake up to this problem:
- Seawater desalination and reverse osmosis. Desalination is an approach being used by many of the countries in the Middle East. The biggest drawback: The process uses an enormous amount of energy. Think about this: Producing four gallons of desalinated seawater could take as much energy as running a lightbulb for one hour. But by using different approaches to reverse osmosis (for example adjusting the water pressure hitting the membrane), you can improve the efficiency of these systems.
- Urban power selection. The electricity supplies that a city chooses will have a direct impact on its water consumption. The National Renewable Energy Lab (obviously a biased source) puts forth this statistic: Each day, the American electricity production from fossil fuels and nuclear energy requires 190 million gallons of water, which is approximately 39 percent of all the freshwater withdrawn. So, in some areas of the country, it could take as much water to turn on a light bulb as you use watering your lawn.
- Water reuse strategies: If you look at the annual corporate sustainability reports of the big beverage makers, notably The Coca-Cola Co. and PepsiCo, you'll notice that they have put a lot of emphasis on using the water they already use in better ways. So, for example, taking the graywater produced by some of their manufacturing processes and using it for cleaning purposes later on in the process. The way that we think about water clarity -- what's potable and what's not -- will probably change dramatically in the coming years.
By the way, this discussion doesn't even consider the whole separate challenge: water for agricultural uses. But the fact remains: we need freshwater to stick around, and it's time we got more serious about it.