A US scientist, Thomas R. Sinclair has warned countries that are rushing into cultivating biofuels in their efforts to reduce dependence on fossil fuels to take into consideration the multiple limits to plant production on earth.
In an article titled “Taking Measure of Biofuel Limits” published in the “American Scientist,” the magazine of Sigma Xi, The Scientific Research Society, he said, “before nations pin big hopes on biofuels, they must face some stark realities, however. Crop physiology research has documented multiple limits to plant production on Earth. To ramp up biofuel crop production, growers must adapt to those limits or find ways around them.”
Professor Sinclair who is a visiting professor in agronomy at the University of Florida and an adjunct professor in crop science at North Carolina State University was also raised on a farm in Indiana.
He writes “in a justified rush to cut fossil fuel consumption, some nations are embracing biofuels as a petroleum alternative at the gas pump. Using sugarcane, Brazil already produces 24.5 billion liters of ethanol a year to fuel car and truck engines.”
“In the United States, annual ethanol production has reached 40 billion liters, or 10 billion gallons. The U.S. Energy Independence and Security Act calls for 144 billion liters of ethanol per year in the U.S. transportation fuel pool by 2022. That equals 25 percent of U.S. gasoline consumption today. No more than about 40 percent is to be produced with maize, an important food and export crop. Non-grain feedstock is supposed to supply the rest,” he added.
In Professor Sinclair’s view there are no means by which humans could bypass the limits of crop production, arguing that “such advances may not be as simple as some predict. Plants and their evolutionary ancestors had hundreds of millions of years to optimize their biological machinery. If further improvements were easy, they would probably already exist.”
He insists that no matter what techniques are developed to expand biofuel feedstock, some basic physical and physiological limitations will still apply.
“Plants cannot be grown without three crucial resource inputs: light, water and nitrogen. Each of those inputs will be needed in substantial quantities, yet their availability in the field is limited. As important, so far plants make use of those resources only at established rates,” he says.
He further states that no matter what techniques are developed to expand biofuel feedstock, plants cannot be grown without three crucial resource inputs: light, water and nitrogen. Each of those inputs will be needed in substantial quantities, yet their availability in the field is limited. As important, so far plants make use of those resources only at established rates. In fact, the close relationship between the available amounts of these resources and the amount of plant mass they can produce—not human demand—will determine how much biofuel the world can produce.
Citing the US as an example he writes, “light, water and nitrogen will be essential for growing biofuel feedstocks. The availability of these resources will be critical to achieving ethanol production goals set by the U.S. Energy and Security Act. Even if the current increase in maize yield can be sustained at 0.1 tonne per hectare per year, the equivalent of 40 percent of today’s U.S. maize crop will be required for ethanol production while other domestic and export demands for maize also must be met.”
Professor Sinclair is emphatic that identifying land area for cellulosic plant production will be even more challenging. Depending on the efficiency of ethanol production from cellulosic feedstock, somewhere between 25 and 50 million hectares of new land must be brought into high and sustainable agricultural production to achieve the required yields.
“Since this land-use conversion would need to take place roughly over a decade, it would be the most extensive and rapid land transformation in U.S. history,” he says.
To complicate matters, land used for cellulosic feedstock must be in regions with sufficient rainfall to achieve needed yields. The amount of water transpired by those crops could be large enough to influence the hydrologic balance of farming regions. An unanswered question is whether stream and aquifer flows from these areas would also remain adequate to meet all local freshwater needs, he writes.
Professor Sinclair’s arguments obviously are worth looking at by biofuel advocates. Besides, it also calls for a critical and objective look in view of the fact that biofuels are competing for scarce land for food cultivation in the face of a global food crisis.