Are Biofuels Crops Sustainable?
A Sustained Effort
New crops produce biofuels,
but are they sustainable?
Established in 2007, Oak Ridge National Laboratory's Bioenergy Science Center (BESC) could be viewed as the heir to decades of innovative environmental research at the laboratory. The first environmental studies at ORNL were conducted in the 1950s. Over the past three decades, researchers developed a comprehensive portfolio of research data from their studies of biofeedstock options and dedicated bioenergy crops. Today the center has more than 80 staff members working on diverse aspects of bioenergy, including systems biology, transportation analysis, and the impact of various bioenergy options on the environment. Their work provides a significant contribution to national and international policy debates. Among the most notable examples of these contributions is the "Billion Ton Study," a 2006 document that explored issues associated with the possibility of sustainably producing one billion tons of biomass feedstock annually in the United States.
Building on this legacy, ORNL's Center for BioEnergy Sustainability (CBES) is emerging as a valuable resource for understanding the challenges of sustaining the growth of biofeedstocks and the environmental considerations necessary for the production and distribution of biofuels and other bio-based products. "One of the center's primary goals is to foster communication among scientific teams at the laboratory as well as among national and international research groups who are studying many of these same issues," says CBES Director Virginia Dale. "We would like to expand their research focus to elements of sustainability along the entire supply chain."
The CBES performs work designed to complement the research at BESC, where scientists are seeking to unlock the secrets of cellulosic biofuels. CBES studies of how soils, economic factors and land use affect where energy crops can be grown dovetail nicely with BESC's development of new and improved poplar and switchgrass feedstocks. "CBES provides valuable information about available land where biomass can best be grown to enhance sustainability," Dale says. "Our researchers employ a suite of computer models to arrive at these determinations. Databases maintained at ORNL and elsewhere contribute to these models, as does the long history of involvement in feedstock development." Robin Graham, leader of ORNL's Renewable Energy Systems group, notes that the Environmental Sciences Division was asked by the Department of Energy in the late 1970s to identify which feedstocks would be suitable for bioenergy. Over the next three decades researchers considered a range of issues, including which species would be good bioenergy candidates, their potential for improvement, the cost of production and factors associated with harvesting and transportation to the biorefinery. "ORNL has always been the lab upon which DOE relied to determine which feedstocks are available now and which ones might be options in "she says.
In recent years, CBES has collaborated with the University of Tennessee and other institutions to design large-scale experiments that examine the environmental, social and economic consequences of biomass production. The experiments enable researchers to compare plantings of traditional crops with bioenergy crops to determine the relative effects on soil, water quality and yield per acre. "When BESC has a bioenergy crop ready for field tests," Dale says, "we have locations and experimental designs for studies that include 'control' groups of traditional crops, along with native and hybrid switchgrass. The studies enable us to compare the effects of growing different bioenergy crops." Designing experiments on a large scale makes it possible for CBES researchers to incorporate ecological factors that are not practical in smaller "field plot" experiments. This analysis in turn provides the BESC with information about the sustainability of potential feedstocks.
"There are always tradeoffs," Dale says. "We would like to find crops and management systems that are compatible with good water quality and soil conditions and that provide a desirable habitat for birds, beneficial insects and other animals. Ideally, growing and harvesting the crop would also result in low greenhouse gas emissions, while allowing farmers to use their existing equipment. And of course, the crops must generate a profit for the farmer. We are working on analytical approaches that consider these tradeoffs."
Graham adds that the data CBES provides on sustainability can be of use to BESC at several stages in the feedstock development process. "Some of the studies we conduct on land use and logistics provide BESC with a framework of desirable characteristics for crops that have high potential for cultivation in a particular area," she says. "Conversely, once the plants are created, we can test them in the field and provide feedback on their potential implications for economic, environmental and social factors."
CBES has an international perspective on developing flexible approaches to cultivation of bioenergy crops. Experience has shown that crops and management practices do not migrate smoothly to every location, requiring different strategies for various regions. The optimum biofeedstock depends on a range of unique factors, including local needs for food crops, soil quality, and the crops local farmers are accustomed to growing.
"International groups are currently in the process of developing standards for feedstocks," Dale says. "We are part of their teams, which is important because conditions for farmers in the U.S. differ greatly from those of farmers in Africa and South America. Considering the full range of approaches is critical to the fieldwork and the modeling of feedstock production."
Both Dale and Graham agree that concerns about the sustainability of feedstocks are intensified by America's goal of replacing a large fraction of oil imports with biofuels. Perhaps fortunately, these concerns are not unique to the United States. The international community has an increasing need for data on the sustainability of biofeedstock production, as well as on the production, use and sustainability of biofuels. Addressing this need will likely shape the next generation of environmental research at Oak Ridge National Laboratory.