Water and Biofuels

Biofuels are grown from biologic feedstock and all living things require water. It is also true that production processes require water as well. Thus, a great deal of water is required to produce fuel from biologic feedstock. With an ever increasing population, limited supplies of clean and fresh water, and increasing energy demands, the sustainability of biofuels is in question if requirements for water cannot be decreased.

Estimates

Water Requirements for Various Biofuel Feedstock Used to Produce Ethanol

Crop

Gallons of Water/Gallon of Ethanol

Corn

1,500

Sugar Beet

1,300

Jatropha

900

Of the estimates in these charts, less than 5% of the total water use is required for processing and delivery of the biofuels. The vast majority of the water used is consumed during agricultural steps. In the U.S. 25-50% of all water is used for agriculture. In Europe, the number is somewhat less than 25%. In regions like South America, the Middle East, and China the amount ranges from 75% to 90%.

Another way of looking at water use is in terms of gallons of water used per mile driven. This offers a unique way of comparing water use of biofuels to water use of petroleum fuels. Comparisons are made for a small car and for a standard pickup truck.

Water Use by Mile for Various Fuels

Fuel Source

Gallons of Water per Mile (Car)

Gallons of Water per Mile (Truck)

Corn

283

444

Grain

0.17

0.28

Cellulosic Biofuel

0.26

0.42

Petroleum

0.04

0.07

Oil Shale

0.08

0.21

Data from Sandia National Laboratories, U.S. Department of Energy and Energy Information Administration

Algae are no better either. To produce just 5% of the fuel needed for the United States transportation sector would require 123 billion liters of water. That is the equivalent of roughly 3.15 liters of water for every liter of biofuel produced in the worst case scenario. In the worst case scenario, up to 3,600 liters of water are needed per liter of fuel produced. That level of water use is simply unstainable.

Already Short

Even without biofuels, the world is experiencing water shortages. Problems are particularly severe in parts of Africa, Southeast Asian, and South and Central America. Estimates are that roughly one-third of less developed countries will have enough water to meet their needs in the year 2025.

Bottom Line

From the charts above, it should be obvious that certain biofuel feedstock cannot be used to sustainably produce biofuels. Some feedstock, like cellulosic feedstock (generally just left over after food crops are harvested) uses much less water, but cannot be obtained on a large-enough scale to meet current fuel demands.