to date, and the amount of N applied to the land is also at or near its highest level. If not addressed through policy and technology development, this effect could accelerate as biofuels expand to 15 percent of domestic usage to meet President Bush’s 2017 goal, or to 30 percent of domestic fuel usage as proposed by President Bush as the ultimate goal.

If projected future increases in the use of corn for ethanol production do occur, the increase in harm to water quality could be considerable. Expansion of corn on marginal lands or soils that do not hold nutrients can increase loads of both nutrients and sediments. To avoid deleterious effects, future expansions of biofuels may need to look to perennial crops, like switchgrass, poplars/willows, or prairie polyculture, which will hold the soil and nutrients in place.

To move toward a goal of reducing water impacts of biofuels, a policy bridge will likely be needed to encourage development of new technologies that support cellulosic fuel production and develop both traditional and cellulosic feedstocks that require less water and fertilizer and are optimized for fuel production. Policies that better support agricultural best practices could help maintain or even reduce water quality impacts. Policies which conserve water and prevent the unsustainable withdrawal of water from depleted aquifers could also be formulated.

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