A systems approach to biofuels sustainability

By Lisa Gibson
Biofuels sustainability can be addressed by considering the agricultural, energy and environmental sectors as one large system, according to "Biofuels, Land and Water: A Systems Approach to Sustainability," a study by Argonne National Laboratory researchers. A problem for one sector could be a resource for another.

"We could find solutions to pressing problems of each [sector] that are not addressed while we keep the sectors compartmentalized," said M. Cristina Negri, one of the researchers who conducted the study. For example, nutrients in impaired water from agricultural runoff could be reused on biofuel crops, providing a potential solution to the inefficiency in the use of agricultural fertilizers near the Gulf of Mexico hypoxic zone, she said. This would be a substitute for costly fertilizers. Hypoxia or "dead zones" occur when the concentration of oxygen in water is decreased to the point where it can no longer support living aquatic organisms. The hypoxia in the Gulf of Mexico is said to be caused by fertilizer runoff from the Mississippi River, which flows through the U.S. Corn Belt.

The study found that using marginal land and degraded water resources in Nebraska can increase biomass feedstock production to meet 22 percent of the state's energy requirements, compared with the current 2 percent. Marginal land resources include riparian and roadway buffer strips, brownfield sites and marginal agricultural land. Degraded water resources used in the study include nitrate-contaminated groundwater and wastewater.

"We wanted to determine if the potential opportunity for resource recovery was large enough to warrant attention," Negri said. "Our conclusion is that it is." Challenges do exist, though, and the team is continuing its work by selecting practical approaches that would create a win-win opportunity for all stakeholders, she said.

There could be a sizeable opportunity for this approach in Nebraska, as about 1.5 million acres were determined to be marginal agricultural land, according to the study, mostly in the western portion of the state. Conservation Reserve Program land accounted for 1.1 million acres in Nebraska in 2007. Possible overlap between land classifications-CRP land classified as cropland or grasslands-is uncertain, though, and merits further investigation, the study says.

Spatial overlap between marginal land and degraded water resources is important in maximizing feedstock productivity, while minimizing the cost of transporting the water to the biomass feedstock, according to the study. In Nebraska, about 2 percent of the CRP land, 44 percent of riparian buffers and 50 percent of roadway buffers overlap with areas of nitrate-contaminated groundwater and livestock farms, the study shows.

"We are now working on other states and on proposing viable ways to make this concept a solution," Negri said. Studies have shown that about 28 percent of available groundwater resources in the U.S. are contaminated with nitrate and would need to be treated prior to use for drinking water, according to the Argonne study.

The systems approach has the potential to significantly improve the economic, social and environmental sustainability of biofuels, the researchers said. The inclusion of other sources of marginal land could contribute significantly to feedstock production for bioenergy, they added. A further advantage of the approach is the possibility of improving wildlife habitat and biodiversity through the development of buffer strips and biomass feedstock fields as habitat corridors.

"Biomass producers would make a profit and could be, at the same time, agents of environmental services," Negri said. "We could redefine the biomass sustainability issue by positively designing ways of growing it that contribute to clean water, greenhouse gas mitigation, rural development and address land-use change, while sustaining high yields and economic profitability."

-Lisa Gibson