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Study Finds Water Use for Switchgrass Ethanol Production Approximately the Same as for Gasoline

23 August 2009

Consumptive freshwater use for ethanol and petroleum gasoline production. Data: Wu, ANL/ESD/09-1. Click to enlarge.

In the US, producing one gallon of ethanol from switchgrass consumes approximately the same net amount of water as does producing a gallon of gasoline from conventional crude or oil sands oil, according to a study by Argonne National Laboratory researchers presented at the 238th national meeting of the American Chemical Society last week.

The production of both bio and petroleum feedstocks and fuels requires substantial water input. Biofuel feedstocks such as corn, switchgrass, and agricultural residues need water for growth and conversion to ethanol; petroleum feedstocks such as crude oil and oil sands also require large volumes of water for drilling, extraction, and conversion into petroleum products. In many cases, the Argonne team noted, crude oil production is increasingly water dependent.

Competing uses strain available water resources and raise the specter of resource depletion and environmental degradation. Water management has become a key feature of existing projects and a potential issue in new ones.

—Wu et al. ANL/ESD/09-1

Consumptive freshwater use for switchgrass ethanol and petroleum gasoline production. Data: Wu, ANL/ESD/09-1. Click to enlarge.

The work examined the growing issue of water use in energy production by characterizing current net consumptive water use in bioethanol produced from corn and from cellulosic feedstocks, gasoline from Canadian oil sands, Saudi Arabian crude, and US conventional crude from onshore wells. The Argonne researchers evaluated water requirements and consumption for two major production stages: feedstock production and feedstock conversion.

The study focused on three USDA farming regions for the production of corn in the United States, in which 89% of corn and 95% of ethanol are produced. For petroleum oil, they selected regions representing 90% of US onshore crude production and 81% of refinery output, 100% of Canadian oil sands production, and 52% of Saudi Arabian oil production. The analysis takes into account regional variations and historic trends in water consumption for the selected fuels.

They examined corn ethanol produced via dry milling and cellulosic ethanol produced via biochemical and thermochemical conversion technologies. The analysis revealed that the amount of irrigation water used to grow biofuel feedstocks varies significantly from one region to another and that water consumption for biofuel production varies with processing technology.

Our study underscores that one of the benefits of using perennial biomass crops, such as switchgrass, is lower water consumption.

—May Wu

Other findings included:

  • Consumptive water use for feedstock and fuel production varies considerably by region, type of feedstock, soil and climatic condition, and production technology for ethanol, as well as by age of oil well, recovery technology, and extent of produced-water reinjection and steam recycling for petroleum gasoline. There are significant regional differences, however, particularly for corn production.

  • Conservation measures to reduce consumptive water use are needed to achieve sustainable ethanol and gasoline production. Improved water management is needed for corn irrigation, particularly in those areas where water is scarce. Cellulosic feedstocks may need to be grown in their native habitat to reduce irrigation. Groundwater use and management are especially critical in arid regions and in locations with high concentrations of biofuel or oil production facilities.

  • In fuel-production facilities, both petroleum gasoline and starch-based ethanol consume little water as a result of historically persistent efforts toward water optimization. For example, ethanol-producing facilities have reduced water consumption by 48% during the past 10 years. This trend is likely to continue and could result in facilities that effectively use net-zero water, at least in some locations in the foreseeable future.

  • Water consumption can be reduced by increasing the use of such measures as steam condensate reuse and treated process water recycling, and by implementing process modifications by means of existing commercial technologies. For cellulosic biorefineries, an integrated process that optimized for water use should be encouraged. Finally, the use of produced-water re-injection for oil recovery should be increased.

  • Groundwater management is extremely important in arid regions and in locations with high concentrations of biofuel or oil production facilities, where a rapid increase in water demand as a result of growing energy demand could have a compounded impact on resources and the environment.

The energy industry is a major consumer of water. As shown in this analysis, consumptive water use varies by process, region, and technology. How a rapid increase of consumptive water use affects water quality is less clear...nutrient releases and toxic contaminant leakage into waterways (surface water and groundwater) can have devastating environmental impacts and, production process discharges have distinctive chemical profiles that can affect downstream wastewater treatment needs, opportunities for treated wastewater recycling, and final solids disposal. At the extreme, degraded water quality can also affect the treatment needed for input water.

Although the required quality of input water varies with type of fuel and feedstock, agricultural crops and biofuel feedstocks generally require higher quality water than that needed for oil E&P (for example, injection water for oil recovery can allow higher levels of total dissolved solids than irrigation water for crops). A study is underway to access potential synergies from using contaminated groundwater for biofuel development. Further investigations will address the impacts on water quality due to various liquid-fuel production processes not only from individual projects, but also from multiple projects for entire regions and over extended periods.

—Wu et al. ANL/ESD/09-1

Projected consumption in 2030. A separate study from Argonne presented at the ACS meeting estimated and compared projected amounts of domestic freshwater consumed in the production of biofuels with the amounts consumed in the production of fossil fuels, electricity generation, and non-energy sectors.

This study found that while total US water consumption is expected to increase by 20% over the 2005-2030 time period, water consumption for energy production is projected to increase by more than 150%, and water consumption for biofuels (biodiesel, corn-based ethanol, and cellulosic ethanol) production is projected to increase by more than 300%. Most of the water consumed in biofuels production (about 70%) is projected to be for corn-based ethanol, with most of this amount for crop irrigation. Between now and 2030, the West North Central Region of the United States is expected to consume the highest amount of water for biofuels production.

The water projected to be consumed in producing corn-based ethanol in 2030—nearly 19 billion gallons per day—is about the same as that projected to be consumed by industrial and commercial production, domestic and public use, and livestock watering combined.


  • May M. Wu, Marianne Mintz, Michael Wang, and Salil Arora. Water consumption in the production of bioethanol and petroleum gasoline (ACS 238, FUEL 309)

  • M. Wu, M. Mintz, M. Wang, and S. Arora (2009) Consumptive Water Use in the Production of Ethanol and Petroleum Gasoline (ANL/ESD/09-1)

  • Deborah Elcock. Projected water consumption for ethanol and biodiesel production relative to other sectors in 2030 (ACS 238, FUEL 308)

August 23, 2009 in Biodiesel, Biomass, Cellulosic ethanol, Ethanol, Fuels, Water | Permalink | Comments (11) | TrackBack (0)


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Why was corn based ethanol (the most used today) water consumption (up to 324 times more water than ethanol) was left out of the second graph.

Most other fuel sources varied between 5.8 to 9.8.

How can one claim that corn based ethanol at 324 is about as about same water consumtion as others sources having a max average of about 7.10 ?

Most people would think that there is a great difference between 324 and 7?

"Why was corn based ethanol water consumption was left out of the second graph[?]"

Um... because it would make it identical to the first graph? The article is titled "Water Use for Switchgrass Ethanol Production Approximately the Same as for Gasoline". The second graph makes that point clear.

Counting angels on the head of a pin here. Commercially viable cellulosic ethanol is and probably always will be five years away. Seems rather unproductive to do all these studies and make all of these predictions about something that does not even exist:

Well, if this is the case, then H2 is quite water-effective:

1kg of H2 = 1 gallon of gasoline; 1kg of H2 will require 9kg of water, since molecular wt. of H2 is 2 and water is 18. 9kg of water = 9 liters = 2.4 gallons of water for every kg of H2.

The second graph plots the same data as the first, but omits corn ethanol because of the scale problem. In other words, with the large range of corn ethanol water consumption represented in the first chart, you can't really see the switchgrass ethanol and gasoline plots.

Pretending that ethanol is not a food because it is made from grass and has chemicals added to it to make it deadly does not eliminate the food fuel issue. Ethanol provides some of the calories that keep many people functioning. There are many people without incomes that would like buy ethanol at $2.00 a gallon to supplement their bread not their gasoline. It also does not eliminate the issue that there is not enough land in the US to supply its energy with biofuels at a cost which will keep the economy running. Stop driving at more than 60 mph if you are truly interested in promoting lower CO2 releases and lower oil imports. ..HG..

Very funny, HG! Pretending that Ethanol is a food in the same straight face that you've pronounced that radiation is not dangerous to health. Ethanol is a poison, HG! Methanol is a far deadlier poison, while Ethanol is a weaker poison which will kill you slowly over a few years, if you imbibe it on a daily basis below lethal dose while building up your tolerance. Many people, though, have died from acute alcohol (Ethanol) overdose, while too many others have killed innocent victims from DUI's (Driving Under Intoxication). As much as 1/2 of motor vehicular fatalities may have been linked to Ethanol intoxication!

People without incomes should not buy Ethanol at all! They should apply for food stamps, and visit food banks frequently, or souplines, until their foodstamp applications are approved, which may take months in this current economic difficulty.

Waste biomass can supply 1/3 of transportation fuel at the current rate in the USA. If waste biomass is converted into H2 and used in FCV's, perhaps 2/3 of transportation fuel requirement will be satisfied, since FC's are twice as efficient as ICE.

Good point Roger. Eventually, couldn't waste biomass be converted directly to electricity for 320 mpg PHEVs + BEVs and many other uses?

Why go through the liquid fuel cycle if (or when) you don't have to?

What is lost in the discussion is that gasoline has a much higher heating value than ethanol.

It would be interseting to see a comparison between bio butanol and gasoline whose heating values are almost the same. Further butanol can be mixed in any quantity with gasoline without causing engine or fuel system problems.

The overwhelming majority of corn is grown without irrigation, relying solely on rainfall. Switchgrass would be even less dependent on irrigation. C4 photosynthesis pathway perennial grasses, like switchgrass (Panicum virgatum) are very water utilization efficient and also have low fertility demand, unlike corn, which requires high fertility.

I am a retired native grass seed farmer who grew unirrigated switchgrass as a commercial crop in southeastern North Dakota. It is possible to increase yields of switchgrass by tapping into two phenomena: winter hardiness and plant phenology.

The ideal cellulosic feedstock is sterile, like Miscanthus giganteus, a naturally occurring sterile hybrid, because seed production makes a huge demand on a plant and requires high fertility. Cellulose production, on the other hand, is comparatively easy on a plant. It is possible to force artificial sterility on switchgrass by taking advantage of its high winter hardiness.

Plant phenology is 95% determined by accumulated heat units, measured in growing degree days. Plant height and volume is determined by water availability and insolation. A southern cultivar of switchgrass can be moved north, ensuring the plant never gets to seed production phase, while at the same time benefiting from the long summer days, but still surviving winter and maintaining its perenniality. Cellulose yields should go up by 50 to 100 percent.

REAP-Canada discovered this phenomenon when testing multiple cultivars of switchgrass at its fields in Quebec. The highest biomass yielder was Cave-in-Rock, of southern Illinois origin, while the lowest yielder was Dacotah of North Dakota origin.


Thank you for the explanation on the second graph. It is logical.

Some switchgrass could be modified to grow on poor land without too much water but yield may go down vs irrigated fields or vs areas with more rain falls.

Possibilities are interesting if small local cellulosic plants can be built and operated by local farm cooperatives on small budgets.

Still cant see how the world could produce enough agrofuels to meet demands without (first) reducing current liquid fuel consumption significantly. PHEVs and BEVs may help to do that.

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