The Copenhagen accord disappointed most of us for various reasons. What rankled me above all was the absence of a pivotal climate change ingredient – water. Copenhagen delegates deliberated on reducing the carbon footprint but neglected the water footprint embedded in any unit of energy. We failed to appreciate that water, energy and climate change are inextricably linked.
Water and energy are cardinal to every aspect of human life. Both are interdependent – water is used in the generation of energy while energy is needed to supply water. Their use depends upon and impacts our eco-system, which is already under stress and running short of both these resources. Further, limitations on water usage are restricting our plans of generating more energy, while energy shortages are curbing our supply of clean water. And this intense competition between the two resources is amplifying with increasing global demand for water and energy, coupled together with climate change effects.
Water Used in Energy
The thermoelectric power sector is the second largest consumer of water resources in the United States, irrigation being the largest. More than 40% of freshwater is used for thermoelectric power generation; albeit a large part of this is recovered with degraded quality and higher temperatures. Water is used extensively, from cradle to grave, in all stages of energy production: resource extraction, refining, processing, electricity generation, storage and transport. Of course, with advancements in technology the fraction of water consumed by power plants is decreasing. However as demand for water increases, it is expected that water will limit our solutions for producing more energy.
Before looking at our water footprint for energy, it is noteworthy to understand two different estimates of water usage available widely – “water consumption” and “water withdrawal.” The former pertains to water that is used-up in energy production (either due to evaporation or contamination etc.) and unfit for returning to the original source. Water withdrawal, on the other hand, refers to removal of water from its original source; whether this water is later consumed or recovered is not accounted for.
Based on this definition, let us look some major water-consuming power plant types and their “water withdrawal” and “water consumption” rates, per MWh of electricity. Although analyzing water consumption would perhaps make more sense, a large part of the existing literature discusses “water withdrawal” rates. I have compiled these numbers together from various sources: EPRI, “Water & Sustainability;” NEI, “Water Use, Electric Power, and Nuclear Energy;” World Economic Forum & Cera, “Thirsty Energy;” Scientific American, “Energy versus Water.”
The industrial and mining sector, which accounts for water consumed in fuel extraction and production, is another water intensive domain. Every day 800 million gallons of petroleum products are refined in the U.S. which consumes 1 to 2 billion gallons of water daily – i.e. 2 to 2.5 gallons of water to produce a gallon of gasoline. And with the ageing of oil and gas wells, this water consumption will increase.
Future energy advancement will put new and higher demands on water. A biofuels and hydrogen economy necessitate considerably more water usage than the fossil fuels used in transportation. Replacing gasoline with biofuels would mean switching to a more water-intensive system. Ethanol or biodiesel production requires 3.45 gallons of water per gallon of biofuel. Similarly, oil shale needs more than 6 gallons of water for every gallon of gasoline.
Countries like China which are facing a severe water crisis have halted their plans of Coals to Liquids primarily because of the strain it would put on their northern water infrastructure. Moreover, low carbon technologies like Carbon Capture and Storage that many nations are depending upon to meet their carbon commitments also require 25% to 33% more water.
The Water-Energy Dilemma…
Our earth has about eight million cubic miles of fresh water. Unfortunately most of our freshwater is not easily accessible and sealed in underground reservoirs and glacial ice. Furthermore, most of the available water is usually not clean and often exists in regions that are far away from human settlements. Cleaning water and transporting it to population centers entails large energy consumption. We cannot build more water cleaning and delivery systems without affecting our energy demand.
Water and Energy: Inseparable Twins
The relationship between water, energy and the environment has been unfortunately watered down time and again in our policy planning process. Water experts need to sit with energy and environment specialists and integrate their planning processes. Otherwise, we will be responsible for implementing contradictory, self-defeating strategies – such as scrubbing coal-fired chimneys to clean coal energy and dumping the sludge in landfills, contaminating water; and of course the controversial use of hydraulic fracing. Incidentally, The Energy and Water Integration Act of 2009 (introduced in March, 2009) which tries to explore the nexus between water and energy, is an indication that this issue is on the government’s radar.
As better policy coordination begins, various solutions could be looked into – viz. switching power plants to dry or hybrid cooling; re-utilizing waste-water (if not for human consumption then at least for power plants and other industries); more efficient desalination of sea water; smart grids intertwining energy and water systems; putting a pragmatic price on water and above all cultivating the discipline of water conservation.
An average American uses 575 liters of water daily, while almost 1.1 billion people lack adequate access using less than 19 liters per day. Due to the abundance of water and its everyday usage, we fail to comprehend its significance and even less of its energy companion. Remember every time you turn on the faucet – you are using energy as well, not just water.
Benjamin Franklin said, “When the well is dry, we learn the worth of water.” Rephrasing in present day context: “When the taps are dry, we will learn the worth of water.”
Energy, Technology, & Policy 
It’s amazing the coverage CO2 gets, yet the immediate impacts of human systems on ecosystem depletion, water cycling and other resource use (which are comparatively well understood, I would argue) seem to not be of concern.
And I just had to say, that water footprint image is awesome.