Liquid costs of biofuel grasses
Some biofuel crops could help to free us from oil but end up exacting an unacceptable cost by devouring precious water resources says a new study into two such crops which are tipped for large scale biofuel production.
A University of Illinois study carried out a detailed analysis effects on water supplies associated with growing miscanthus and switchgrass, which have been tipped as a possible alternative to corn as a biofuel crop.
The team, who publish their results in the Proceedings of the National Academy of Science (PNAS), found that the dense foliage and consequent transpiration (the natural evaporation of water from a plants leaves) of large amounts of water means growing the plants for fuel might not be as efficient as previous analysis has suggested.
"While we are looking for solutions for energy through bioenergy crops, dependence on water gets ignored, and water can be a significant limiting factor," said Praveen Kumar, the Lovell Professor of civil and environmental engineering at the University of Illinois.
"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."
Growing large crops of miscanthus and switchgrass produces a better yield of usable biomass than corn, but will leave soils dry and the air humid says Kumar. And, as climate change starts to affect global weather conditions, the negatives will increase according to the sophisticated modelling pioneered in this study. While, some climates will still be able to support production of these two crops, areas which rely on irrigation will simply find the thirsty plants too expensive.
"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."
Top Image Credit: Miscanthus grass intended for fuel growing in a field © hmproudlove