Maize is now a major source not only of food and animal feed, but also of renewable energy and fuel. However, this state of affairs is not without controversy; campaigners have claimed that a reliance on maize for energy is leading to new land being converted to agriculture to make up the deficit in food production, and is contributing to food price volatility.

Arguments over the multiple uses of maize have raged for years now, and researchers at the University of Illinois have this week waded into this ‘food versus fuel’ debate, having quantified and compared different issues along the entire production system of maize grown for food and for fuel.

As part of a National Science Foundation project studying the environmental impact of agriculture in the U.S., Civil and environmental engineering professor Praveen Kumar and graduate student Meredith Richardson from the University of Illinois used an ‘ecosystem services’ model called ‘critical zone services’ to look at crops’ impacts on the environment in monetary terms.

Prof Kumar explained, "The critical zone is the permeable layer of the landscape near the surface that stretches from the top of the vegetation down to the groundwater. The human energy and resource input involved in agriculture production alters the composition of the critical zone, which we are able to convert into a social cost."

Discussing how they compared the energy efficiency and environmental impacts of maize grown for food and biofuels, Meredith Richardson said, "There are a lot of abstract concepts to contend with when discussing human-induced effects in the critical zone in agricultural areas. We want to present it in a way that will show the equivalent dollar value of the human energy expended in agricultural production and how much we gain when corn is used as food versus biofuel."

Kumar and Richardson accounted for numerous factors in their analysis, including assessing the energy required to prepare and maintain the landscape for agricultural production for maize and its conversion to biofuel. Then, they quantified the environmental benefits and impacts in terms of critical zone services, representing the effects on the atmosphere, water quality and the crop's societal value, both as food and fuel.

In monetary terms, their results show that the net social and economic worth of maize for food in the U.S. is $1,492 (£1,178) per hectare, versus a $10 per hectare loss for biofuel corn production, so a gap of $1,502/ ha between the two.

"One of the key factors lies in the soil," Richardson said. The assessment considered both short-term and long-term effects, such as nutrients and carbon storage in the soil. "We found that most of the environmental impacts came from soil nutrient fluxes. Soil's role is often overlooked in this type of assessment, and viewing the landscape as a critical zone forces us to include that.”

"Using corn as a fuel source seems to be an easy path to renewable energy," said Richard Yuretich, the NSF program director for Critical Zone Observatories. "However, this research shows that the environmental costs are much greater, and the benefits fewer, than using corn for food."