Civil and environmental engineering professor Ximing Cai, left, and graduate student Xiao Zhang performed a global analysis of marginal land that could produce biofuel crops. Credit: L. Brian Stauffer
Using detailed land analysis, Univ. of Illinois
researchers have found that biofuel crops cultivated on available land could
produce up to half of the world’s current fuel consumption—without affecting
food crops or pastureland.
Published in the journal Environmental
Science and Technology, the study led by civil and environmental
engineering professor Ximing Cai identified land around the globe available to
produce grass crops for biofuels, with minimal impact on agriculture or the
Many studies on biofuel crop viability focus on biomass
yield, or how productive a crop can be regionally. There has been relatively
little research on land availability, one of the key constraints of biofuel
development. Of special concern is whether the world could even produce enough
biofuel to meet demand without compromising food production.
“The questions we’re trying to address are, what kind of
land could be used for biofuel crops? If we have land, where is it, and what is
the current land cover?” Cai said.
Cai’s team assessed land availability from a physical
perspective—focusing on soil properties, soil quality, land slope, and regional
climate. The researchers collected data on soil, topography, climate, and
current land use from some of the best data sources available, including remote
The critical concept of the Illinois study was that only marginal land
would be considered for biofuel crops. Marginal land refers to land with low
inherent productivity, that has been abandoned or degraded, or is of low
quality for agricultural uses. In focusing on marginal land, the researchers
rule out current crop land, pasture land, and forests. They also assume that
any biofuel crops would be watered by rainfall and not irrigation, so no water
would have to be diverted from agricultural land.
Using fuzzy logic modeling, a technique to address
uncertainty and ambiguity in analysis, the researchers considered multiple
scenarios for land availability. First, they considered only idle land and
vegetation land with marginal productivity; for the second scenario, they added
degraded or low-quality cropland. For the second scenario, they estimated 702 million
hectares of land available for second-generation biofuel crops, such as
switchgrass or miscanthus.
The researchers then expanded their sights to marginal
grassland. A class of biofuel crops called low-impact high-diversity (LIHD)
perennial grasses could produce bioenergy while maintaining grassland. While
they have a lower ethanol yield than grasses such as miscanthus or switchgrass,
LIHD grasses have minimal environmental impact and are similar to grassland’s
natural land cover.
Adding LIHD crops grown on marginal grassland to the
marginal cropland estimate from earlier scenarios nearly doubled the estimated
land area to 1,107 million hectares globally, even after subtracting possible
pasture land—an area that would produce 26% to 56% of the world’s current
liquid fuel consumption.
Next, the team plans to study the possible effect of climate
change on land use and availability.
“Based on the historical data, we now have an estimation for
current land use, but climate may change in the near future as a result of the
increase in greenhouse gas emissions, which will have effect on the land
availability,” said graduate student Xiao Zhang, a co-author of the paper.
Former postdoctoral fellow Dingbao Wang, now at the University of Central
Florida, also co-wrote the paper.
“We hope this will provide a physical basis for future
research,” Cai said. “For example, agricultural economists could use the
dataset to do some research with the impact of institutions, community
acceptance and so on, or some impact on the market. We want to provide a start
so others can use our research data.”
The Energy Biosciences Institute at U. of I.
and the National Science Foundation supported the study.