The US National Academy of Sciences has produced a study Water Implications of biofuels production. The key points are:
Water is an increasingly precious resource used for many purposes including drinkingand other municipal uses, hydropower, cooling thermoelectric plants, manufacturing, recreation,habitat for fish and wildlife, and agriculture. The ways in which a shift to growing more energycrops will affect the availability and quality of water is a complex issue that is difficult tomonitor and will vary greatly by region.
In some areas of the country, water resources already are significantly stressed. Forexample, large portions of the Ogallala (or High Plains) aquifer, which extends from west Texasup into South Dakota and Wyoming, show water table declines of over 100 feet. Deterioration inwater quality may further reduce available supplies. Increased biofuels production adds pressureto the water management challenges the nation already faces.
In the next 5 to 10 years, increased agricultural production for biofuels will probably notalter the national-aggregate view of water use. However, there are likely to be significantregional and local impacts where water resources are already stressed.
All else being equal, the conversion of other crops or non-crop plants to corn will likelylead to much higher application rates of N, which could increase the severity of the nutrientpollution in the Gulf of Mexico and other waterways. However, it should be noted that recentadvances in biotechnology have increased grain yields of corn per unit of applied N and P.
In addition, biotechnologies are being pursued that optimize grain production when thegrain is used for biofuel. These technologies could help reduce water impacts by significantlyincreasing the plants’ efficiency in using nitrogen, drought and water-logging tolerance, andother desirable characteristics.
A biorefinery that produces 100 milliongallons of ethanol per year would use the equivalent of the water supply for a town of about5,000 people.
Cellulosic feedstocks, which have a lower expected impact on water quality in most cases(with the exception of the excessive removal of corn stover from fields without conservationtillage), could be an important alternative to pursue, keeping in mind that there are manyuncertainties regarding the large-scale production of these crops
.That is a good point about excessive removal of corn stover, or other types of cellulose for future biofuel production, if too much is taken then soil quality will decline. I particularly like the report’s calls for more imagination than a straight cash payment per gallon of ethanol produced, and the policy might call for payments when policy goals are achieved and
To move toward a goal of reducing water impacts of biofuels, a policy bridge will likelybe needed to encourage development of new technologies that support cellulosic fuel productionand develop both traditional and cellulosic feedstocks that require less water and fertilizer andare optimized for fuel production. Policies that better support agricultural best practices couldhelp maintain or even reduce water quality impacts. Policies which conserve water and preventthe unsustainable withdrawal of water from depleted aquifers could also be formulated.
For most of these points the volume of biofuels produced is the key as more is produced then the effects will be greater.
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