Powering Mobility: Water and Your Daily Commute

Air & Water Quality

Posted on: Wednesday, September 14, 2011

Have you ever wondered how much water your vehicle uses? Considering most vehicles are powered by gasoline, the question of how much water they use seems strange. However, when scrutinized, it does indeed take water to extract, produce and transport gasoline and other transportation fuels. So, in reality, all vehicles use a certain amount of water when getting you from A to B.

According to the EPA, “Water is used throughout the energy sector, including in resource extraction, refining and processing, electric power generation, storage, and transport” (U.S. Environmental Protection Administration, “Energy Demands on Water Resources: Report to Congress on the Interdependency of Energy and Water," December, 2006).

By the time you put gasoline into your car and drive 100 miles, you will have used 10.5 gallons of water (King, C.W., Webber, M.E., “Water Intensity of Transportation," Environmental Science and Technology. 42(21): 7866-7872). Diesel is actually slightly less water intensive at 8 gallons per 100 miles driven.

When gasoline is combined with the EPA-required 10% ethanol blend (meaning the ethanol is manufactured from irrigated corn), water usage skyrockets to 200 gallons of water for each 100 miles driven (GWPC, Matthew Mantell, P.E., “Deep Shale Natural Gas and Water Use”). Interestingly enough, the EPA is considering rules that would increase the percentage of ethanol blended with gasoline to 15%.

It is also interesting to note that electric cars use three times more water than gasoline powered cars. This is primarily due to increased water cooling of thermoelectric power plants that generate the electricity (King, C.W., Webber, M.E., “The Water Intensity of the Plugged In Automotive Economy,” Environmental Science and Technology. 42(12): 4306-4311). It is not hugely detrimental that electric cars have a higher water usage; however, it is important to recognize the potential impact on regional water resources.

It turns out that compressed natural gas (CNG) is one of the most efficient transportation fuels in terms of water usage, using 3 gallons of water for every 100 miles driven. Only biodiesel from non-irrigated soybeans uses less water. Unfortunately, biodiesel from non-irrigated soybeans is not scalable to be a significant transportation fuel. On the other hand, CNG is scalable due to the vast supplies of natural gas that have been discovered in gas shales around the country.

At one stage or another, it is inevitable that energy needs water to be produced: “The fact is that all forms of energy use water in its extraction, processing and transportation,” notes the EPA. “Refinery use of water for processing and cooling is about 1 to 2.5 gallons of water for every gallon of product. The United States refines nearly 800 million gallons of petroleum products per day" (EIA, 2006). Therefore, refining uses 1 to 2 billion gallons of water per day. Natural gas processing and pipeline operations use an additional 0.4 billion gallons per day.

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When it comes to electricity generation, the amount of freshwater required is significant: 59 billion gallons of seawater and 136 billion gallons of freshwater per day, according to the EPA (EPA, 2006).

“While these plants do not consume large volumes of water, the availability of large volumes of water is critical to plant operation. Additionally, the intake and discharge of large volumes of water by these plants have potential environmental consequences. Aquatic life can be adversely affected by impingement on intake screens or entrainment in the cooling water and by the dis-charge of warm water back to the source.”

In conclusion, all forms of energy production use water; therefore, all forms of motorized transportation use water. However, the amount of water used for transportation varies greatly depending on what type of transportation fuel. Ethanol uses a significant amount of water, as do electric vehicles. Gasoline and diesel powered cars and trucks use 8 to 10 gallons of water per 100 miles driven whereas CNG (compressed natural gas) vehicles use only 6.5 gallons per 100 miles driven.