University of Illinois at Champaign’s Praveen Kumar has some non-enthusiast news, “While we are looking for solutions for energy through bioenergy crops, dependence on water gets ignored, and water can be a significant limiting factor.”

Kumar, the Lovell Professor of civil and environmental engineering at UI Champaign said, “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 led a study, published this week in the Proceedings of the National Academy of Science Early Edition, detailing effects to the hydrologic cycle of large-scale land conversion, both now and as growing conditions change in the future.  Briefly, the study found that miscanthus and switchgrass lose more water to the air than corn and predicts a resulting reduction in soil moisture and runoff, but an increase in atmospheric humidity. Areas that rely on irrigation could have less water to meet higher demands, which could increase the net cost of land conversion and put pressure on already stressed water resources.

Simple adoption isn’t likely to work – some forethought and planning will be required to trigger a cultivation of miscanthus and switchgrass.  And not all the forecasted area is going to work out.

Switchgrass Growing in Front of Miscanthus. Click image for more info. More photos on the U of I press release page.

Lots of energy researchers and environmental advocates are excited about the prospect of gaining more efficient large-scale biofuel production by using large grasses like miscanthus or switchgrass rather than corn. They have investigated yields, land use, economics and more, but one key factor of agriculture has been overlooked: the rain water.

Miscanthus and switchgrass have a very different aboveground foliage structure from corn – more surface area and much denser growth. This is good for maximizing the amount of biomass that an acre of land can produce, but it also increases water use. Miscanthus and switchgrass intercept light and rain differently from corn, and lose more water through transpiration, causing them to pull more water from the soil. The result of large-scale adoption would be a reduction in soil moisture and runoff, but an increase in atmospheric humidity.

Kumar, who also is affiliated with the UI department of atmospheric sciences speaks to the consequences, “All these together account for the changes in hydrology, just from land-use change. Then, if you impose further – higher carbon dioxide in the atmosphere, higher temperatures and changes in rainfall patterns – they add further modulation to the water use pattern.”

Kumar’s group used a sophisticated model it developed to study crops’ fine sensitivities to temperature and carbon dioxide changes in the atmosphere. The model incorporates the acclimation response of plants to changing climate.

Using their predictive model, Kumar’s research group found that the net water use would increase further as a result of rising temperatures and carbon dioxide. Higher levels of carbon dioxide alone make the plants more water-efficient, since their pores are open less time to absorb carbon dioxide. However, rising temperatures counteract this effect, as the plants will transpire more while their pores are open, losing more water than they save.

This additional water loss compounds the increase in water usage from land conversion. In the U.S. Midwest, rainfall should remain sufficient to meet water demand, according to Kumar. However, areas that rely on irrigation could find they have less water to meet higher demands, which could increase the net cost of large-scale land conversion and put pressure on already stressed water resources.

“If we’re going to solve energy problems through bioenergy crops, there are collateral issues that need to be considered,” Kumar 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. The cost of that should be factored in to the decision making.”

On the other hand . . . Professor Kumar went pretty far.  Going into climate change from the research is pushing the envelop into incredulity for most thoughtful assessment.  Presumption of anthropological forcing of changing the climate serves masters other than the citizens of the state and nation.  Yet the hard science, insofar as discussed does tell us that rainfall, soil moisture and water respiration back into the air deserves some forethought on the potential of the great grasses.

From the study we can ascertain that miscanthus and switchgrass are going to be even more susceptible to rain events.  Watching the markets of today of the contemporaneous crops of corn and soybeans that demand less rain tells us that pricing will be weather dependent to some extent.  That OPEC might seem benign compared to mother nature for many.   Soil composition from the surface down into the plants root zones, across the arable surface, have vastly different water holding capacities.  This is another consideration for farmers and cultivars.  But no comparison of net product was presented in the press release, leaving readers with no sense of the benefits from the choices between current crops and a change to the great grasses.

For most observers the Professor and his team offer important work and worthy results.  Those on the land would be asking questions on these topics before adopting a farming plan.  Maybe observers should wonder what the producers in the future might be considering – just as Kumar and his team have done.


1 Comment so far

  1. MattMusson on August 30, 2011 7:48 AM

    It is important that this type of evaluation is done prior to large scale conversion to these crops.

    If your aim is to lower the amount of CO2 in the atmosphere, you don’t want to use all the water and deplete the soil in the process.

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