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National Research Council Warns on Water Impact of Accelerating Biofuels Production

Irrigated land in the US. Click to enlarge. Source: NRC

Although biofuels production currently entails a marginal additional stress on water supplies at the regional to local scale, the significant acceleration of biofuels production could cause much greater water quantity problems depending on where the crops are grown, according to a new report from the National Research Council of the US National Academies.

Growing biofuel crops in areas requiring additional irrigation water from already depleted aquifers is a major concern. Furthermore, if projected future increases in the use of corn for ethanol production do occur, the increase in harm to water quality could be considerable, the report authors conclude.

The National Academies comprise the National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council. The Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering.

Noting that water is an increasingly precious resource, the National Research Council convened a committee to study how shifts in the nation’s agriculture to include more energy crops, and potentially more crops overall, could affect water management and long-term sustainability of biofuel production. In support of the work, the Water Science and Technology Board (WSTB) of the National Research Council convened a colloquium in July 2007 to address five basic issues:

  1. Crop water availability and use. How much water and land might be required to grow different kinds of biomass in different regions? Where is water availability likely to be a limiting factor?

  2. Water quality. What are the possible, or likely, water quality effects associated with increases in production of different kinds of biomass?

  3. Reducing water impacts through agricultural practices. What promising agricultural practices and technologies might help reduce water use or minimize water pollution associated with biomass production?

  4. Water impacts of biorefineries. What are the water requirements of existing and proposed production plants, and what water quality problems may be associated with them?

  5. Key policy considerations. What policy, regulatory, and legal changes might help address some of these water use and water quality issues?

The report is based on the findings presented at the colloquium.

Crop water availability and use. The committee found that agricultural shifts to growing corn and expanding biofuel crops into regions with little agriculture, especially dry areas, could change current irrigation practices and greatly increase pressure on water resources in many parts of the United States.

In the next 5 to 10 years, increased agricultural production for biofuels will probably not alter the national-aggregate view of water use. However, there are likely to be significant regional and local impacts where water resources are already stressed.

The water resource is already stressed in many agricultural areas. For example, large portions of the Ogallala (or High Plains) aquifer, which extends from west Texas up into South Dakota and Wyoming, show water table declines of over 100 feet. Colorado River reservoirs are at their lowest levels in about 40 years. And over-irrigation in areas such as the San Joaquin Valley of California has led to salinization of the soils. This should be kept in mind when utilizing today’s water use as a baseline for comparison of future water-availability scenarios.

Regional irrigation water application for various crops for six regions of the United States. Irrigation application is normalized by area, and is in feet. Click to enlarge. Source: NRC

The amount of rainfall and other hydroclimate conditions from region to region causes significant variations in the water requirement for the same crop, the report says. For example, in the Northern and Southern Plains, corn generally uses more water than soybeans and cotton, while the reverse is true in the Pacific and mountain regions of the country. Water demands for drinking, industry, and such uses as hydropower, fish habitat, and recreation could compete with, and in some cases, constrain the use of water for biofuel crops in some regions. Consequently, growing biofuel crops requiring additional irrigation in areas with limited water supplies is a major concern.

Even though a large body of information exists for the nation’s agricultural water requirements, fundamental knowledge gaps prevent making reliable assessments about the water impacts of future large scale production of feedstocks other than corn, such as switchgrass and native grasses. In addition, other aspects of crop production for biofuel may not be fully anticipated using the frameworks that exist for food crops. For example, biofuel crops could be irrigated with wastewater that is biologically and chemically unsuitable for use with food crops, or genetically modified crops that are more water efficient could be developed.

Water Quality Impacts. The quality of groundwater, rivers, and coastal and offshore waters could be impacted by increased fertilizer and pesticide use for biofuels, the report says. High levels of nitrogen in stream flows are a major cause of hypoxic regions, commonly known as “dead zones”. (Earlier post.)

The report notes that there are a number of agricultural practices and technologies that could be employed to reduce nutrient pollution, such as injecting fertilizer below the soil surface, using controlled-release fertilizers that have water-insoluble coatings, and optimizing the amount of fertilizer applied to the land.

One metric that can be used to compare water quality impacts of various crops are the inputs of fertilizers and pesticides per unit of the net energy gain captured in a biofuel. Of the potential feedstocks, the greatest application rates of both fertilizer and pesticides per hectare are for corn. Per unit of energy gained, biodiesel requires just 2 percent of the N and 8 percent of the P needed for corn ethanol. Pesticide use differs similarly. Low-input, high-diversity prairie biomass and other native species would also compare favorably relative to corn using this metric.

The switch from other crops or non-crop plants to corn would likely lead to much higher application rates of highly soluble nitrogen, which could migrate to drinking water wells, rivers, and streams, the committee said. When not removed from water before consumption, high levels of nitrate and nitrite—products of nitrogen fertilizers—could have significant health impacts.

Agricultural practices. The reports points to many agricultural practices and technologies that, if employed, can increase yield while reducing the impact of crops on water resources.

Many of these technologies have already been developed and applied to various crops, especially corn, and they could be applied to cellulosic feedstocks. Technologies include a variety of water-conserving irrigation techniques, soil erosion prevention techniques, fertilizer efficiency techniques, and precision agriculture tools that take into account site-specific soil pH (acidity, alkalinity), soil moisture, soil depth, and other measures.

Biorefineries. For biorefineries, the water consumed for the ethanol production process—although modest compared with the water used growing biofuel crops—could substantially affect local water supplies, the committee concluded. A biorefinery that produces 100 million gallons of ethanol a year would use the equivalent of the water supply for a town of about 5,000 people. Biorefineries could generate intense challenges for local water supplies, depending on where the facilities are located. However, use of water in biorefineries is declining as ethanol producers increasingly incorporate water recycling and develop new methods of converting feedstocks to fuels that increase energy yields while reducing water use, the committee noted.

Policy considerations. As total biofuels production expands to meet national goals, the long-term sustainability of the groundwater and surface water resources used for biofuel feedstocks and production facilities will be key issues to consider, according to the report.

From a water quality perspective, it is vitally important to pursue policies that prevent an increase in total loadings of nutrients, pesticides, and sediments to waterways. It may even be possible to design policies in such a way to reduce loadings across the agricultural sector, for example, those that support the production of feedstocks with lower inputs of nutrients.

The authors suggest that creative alternatives to a simple subsidy per gallon produced could help protect water quality. For example, performance subsidies could be designed to be paid when specific objectives such as energy conversion efficiency and reducing the environmental impacts of feedstock production—especially water quality—are met.

Biofuels production is developing within the context of shifting options and goals related to US energy production. There are several factors to be considered with regard to biofuels production that are outside the scope of this report but warrant consideration. Those factors include: energy return on energy invested including consideration of production of pesticides and fertilizer, running farm machinery and irrigating, harvesting and transporting the crop; the overall “carbon footprint” of biofuels from when the seed is planted to when the fuel is produced; and the “food vs. fuel” concern with the possibility that increased economic incentives could prompt farmers worldwide to grow crops for biofuel production instead of food production.

The study was sponsored by the McKnight Foundation, Energy Foundation, National Science Foundation, US Environmental Protection Agency, and National Research Council Day Fund.



Harvey D

This could mean that current "oil wars' may be replaced with future 'water wars'to keep biofuel guzzlers on American roads and produce enough affordable price food.

Lets hope that North American drivers will change their attitude and start driving smaller-lighter more efficient PHEVs and BEVs before we get to that point. Will we?

Wonder if the Groenland + South pole glaciers could be harvested before they melt or slide into the ocean.
It may be a better solution than a 'water war' with Canada to gain access to Canadian fresh water?

Rafael Seidl

This is what happens when you subsidize specific crops (corn) and then throw in protectionist tariffs on the specific products produced from them (ethanol).

Remove or at least reduce the incentives and he negative side effects will ease considerably. There are other ways to buy votes in the Midwest, e.g. by paying farmers for sequestering airborne CO2.


Yes Harvey, it is nothing short of a miracle that the US has not already invaded Canada to steal its oil resources. That is, after all, what America does.

fred schumacher

Except for Nebraska, most irrigated land is not for corn production. In the west it's primarily for alfalfa, vegetables and fruit tree crops.

The corn ethanol boom is a temporary phenomenon. Already the bloom has come off the rose and future expansion has been scaled backed. The long term future of American-sourced biofuels (other than algae origined) will be from perennial crops, which are low-fertility plants, quite the opposite of corn.

A shift from cereal agriculture to perennial biomass crops will result in a reduction in water demand and fertilizer and chemical run-off.

Harvey D

fred S.

I agree with you. A massive switch to cellulosic ethanol and/or butanol using higher nitrogen fixation tall grass and similar perennial biomass crops would use less fresh water, less fertilizer and would reduce unwanted nitrogen runoffs. Almost too good to be true!

However, since cellulosic ethanol production cost much more than the corn-grain-cane approach, we all know that production cost + profit will dictate for many more years.

Running out of fresh water may be one of the element required for the switch to cellulosic. Don't you think that some politicians + corn lobbies may prefer a 'water war'?


The US doesn't need to invade Canada for oil or anything else. If there's a resource they want, they'll lean on a Canadian politician to sign a "free trade" agreement. (free access to Canadian resources in exchange for access to US markets when it suits the US - google "softwood lumber dispute") Whoops, they've already done that, we've already lost control over our oil resources. Now some US state department guy is running around saying that the US has no designs on our water. Ya, right. Big powers don't have friends, just interests.

tom deplume

A couple questions come to mind from looking at the map. Are the irrigation figures based on only one year's use or an average of many years? Two areas seem out of place, eastern Arkansas and southern Florida. Aren't these some of the rainiest parts of the country?

Harvey D


Neil may have the answer to your question. Existing Free Trade Agreement may be used to justify diverting (exporting) billions of tons of fresh water south of the border every year.

If we could get a high enough price i.e. something like (10%) of what we are getting for oil (4 to 6 cents/L), it may pay for our national health care system @ $110+ billion/year. This would be about equivalent to our oil export to USA @ $100 to $120/barrel

Oil, Water, electricity and uranium may be our future major exports to USA, if the price is right.


Very true, Harvey.

Most (not all) Canadian regions adjasent to US border have huge surplus of surface water flow. It is much more sensible to sell last year snow, rather than finite mineral resourses.


Wasn't there a suggestion that the US dig a canal from the gulf of Baja to the Sonora desert, so as to bring in salt water for alga culture? Sounds hugely expensive, but then, we built canals in earlier eras to to save fuel and time for shipping, and this could be replace billions of barrels of imported it could possibly make economic sense. California has 3 canals that run hundreds of miles from the moist North to the dry South...same deal.

I wonder how much water is needed to process the oil crops and ferment the alcohols? Is a big part of the research going to be about refining biofuels with minimal water lost in the refining process?
Growing Elephant grass or switch grass without irrigation won't help us much if the cracking and fermenting processes require vast amounts of fresh water.

Harvey D

Since current tranportation vehicles use about 35 times the energy used to feed USA/Canada people, agrofuel will not be a sustainable solution unless we can drastically reduce or change the energy used by transport vehicles.

A better approach would be the progressive (but quick) ELECTRIFICATION of most if not all ground transportation vihicles. Electric vehicles are much cleaner and about 2.20 to 2.43 times more efficient than the most efficient ICE units.

Current Solar panels produce clean electric energy much more efficiently than grain and even cellulosic ethanol and ICE vehicles and it is sustainable for many centuries to come. A few hundred billion $$ invested in Solar Power R&D and Solar energy production and distribution would do much more to reduce GHG and global warming than 1000 ethanol plants.

Of course, we could complement Sun Power with a mixture of Wind, Geothermal, Waves, Hydro and Nuclear power. Dirty coal fired plants should shut down unless their GHG can be captured and safely stored or transformed.


I recently saw an article about the limitations of replacing fossil fuel consumption with fresh plant agrofuels. Thought it may be of interest to anyone who wanted some more source material. I personally don't like the use of crop plants for fuel production though I can see its short term benefits in creating infrastructure and awareness. Hopefully we can move away from it to more sustainable ways as well as realizing that a harder look into the way our lifestyles effect fuel consumption and what we can do to lessen our impact.

As for the surplus of water. Just look at the complaints of the use for it for tar sands oil production. There is a limit on how much can be diverted south into the US without major costs being incurred somewhere. Even presently, Canada and the US have treatys describing what can be diverted for what (like in Niagra Falls) although there seems to be ambiguity at a national level about water exploitation protection in Canada.

Paper prepared for the 20th Round Table on Sustainable
Development of Biofuels: Is the Cure Worse than the Disease? OECD.


Switchgrass grew on the American plains long before irrigation. There are 50 million acres growing it now to preserve the soil. Mow it and make fuel.


First of all, it should be made clear that corn and soybeans are already well established crops/commodities in our country. They are grown regardless of the renewable fuels industry for animal feed. An entire infrastructure is already in place to grow, harvest and transport these crops.

Now add in the renewable fuels of biodiesel and ethanol. In the case of soybeans the grain is crushed and the oil is washed out of the flakes. Most animals cannot digest the fat in soybeans so this process has always been used in the feed industry. The oil was once considered a waste product and often dumped for lack of a market, but now it is refined and used as fuel. This process is not taking food from anyone’s plate nor is it taking more fuel to produce than it makes. According to the US Dept of Energy and USDA for every unit of petroleum fuel used to grow the crop, harvest it, transport it, refine it and get it to market 3.2 units of bio energy are gained. Ethanol is made from corn using a fermentation process and is not quite as efficient as biodiesel with 1.67 units of bio energy gained but once again yields valuable animal feed called dried distiller’s grains. The food chain remains unbroken here as well.

In light of this information how can you complain that these renewable resources are not viable? In fact, if you know the crops will be grown regardless and will continue in the food chain you could go so far as to only include the process of refining the fuel and bringing it to retail market into the energy ratio. Then look at the fact that these fuels are cleaner burning, even when blended as low as 5 or 10% with petroleum fuel in your vehicle’s tank, how can you afford to dismiss them? Conversely, some recommend growing switchgrass for biomass and cellulosic ethanol instead of soybeans and corn. I question the logic behind using a plant stock that has no other value. Switchgrass is not a plant to grow for any kind of livestock forage or feed, why not choose a feedstock with multiple uses including seed oil, biomass AND food?

Active pursuit of all sources of renewable fuels is urgently needed. Algae, wind, biomass - you name it we need to look at it. However we are able to make ethanol and biodiesel RIGHT NOW, how far off are other fuels? I often wonder how much we would have gained had we taken “gasohol” seriously back in the seventy’s. I am happy to hear of ongoing research in multiple forms for renewable energy, especially when we started thirty years after our first wake up call on petroleum fuels!


Again a total disregard for semi arid agricultural methods! Africa, India and even Texas has plenty of potential for Jatropha that actually stabilises soil and reduces water runoff. Like wize elephant grass root system actually benefits soil enabling parallel food crop growth. Just look at Kenyan projects!

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