University of Illinois researchers say they've conducted a study of the water cycle involved in large-scale land conversion to those grasses, and found that while it can maximize the amount of biomass an acre of land can produce, it also increases water use, a UI release reported Monday.
"While we are looking for solutions for energy through bioenergy crops, dependence on water gets ignored, and water can be a significant limiting factor," Praveen Kumar, a professor of civil and environmental engineering, said.
Miscanthus and switchgrass have a very different above-ground foliage structure from corn -- more surface area and much denser growth.
But this means they lose more water through transpiration, causing them to pull more water from the soil.
"There are many countries around the world that are looking into biofuel energy, but if they are adopting these (large grasses) into their regular policy, then they need to take into account the considerations for the associated demand for water," Kumar said.
"If we're going to solve energy problems through bioenergy crops, there are collateral issues that need to be considered," he said. "Water is a significant issue. It's already a scarce resource across the globe, and the need for it is only going to increase."