November 2008, Vol. 20, No.11
Corn-Based Ethanol Not Best Choice, Researchers Say
The most sustainable and ecologically promising source of biofuel is not corn-based ethanol, according to a new study conducted at the University of Washington (UW; Bothell). According to a UW press release, university researchers have determined that more-precise calculations are needed to determine the ecological footprints of large-scale cultivation of crops used to produce biofuel.
During the yearlong study, UW scientists and the Nature Conservancy (Arlington, Va.) looked at a variety of published research on different sources of biofuel to identify the sources with the lowest ecological footprints. By taking into consideration the net gain in energy, the impacts to soil fertility, and the effects on food supply from each source’s cultivation, the scientists determined that corn-based ethanol is the worst alternative.
Because such large amounts of energy are required to grow and convert corn to ethanol, corn-based ethanol results in only a modest net energy gain, the press release says. Using another crop, such as switchgrass or algae, would use significantly less energy to produce fuel, but the technology to achieve this has not been fully developed, according to the press release.
With escalating prices and pressure to find less costly fuel, Martha Groom, lead researcher for the study, warned that hastily committing to another fuel source could cause myriad other problems. If farmers plant only corn without rotating other crops, soil depletion could result, which would limit crop growth and cause soil erosion, she said.
“It’s foolish to say we should be developing a particular biofuel when that could mean that we’re just replacing one problem with another,” Groom said.
The study also considered the amount of carbon dioxide plants absorb, compared to the amount they are responsible for creating by requiring fertilization or cultivation using farm equipment. In addition, energy required from watering and harvesting was considered.
The scientists used the information found regarding each crop’s sustainability to create a set of policy recommendations. The 12 recommendations are designed to help policy-makers, students, and biologists establish a basis for developing biofuel and identify areas to establish new research in an effort to find the most ecological fuel source. The policy suggestions are starting points in the search for proper answers, Groom said.
Policy recommendations include the following:
Calculate a biofuel’s ecological footprint.
Promote only biofuels that can be produced sustainably.
Select highly efficient species for biofuels.
Work to minimize land needed for biofuels.
Encourage reclamation of degraded areas.
Prohibit clearing areas for more cultivation.
Promote use of energy crops that require less fertilizer, pesticide, and energy.
Promote native and perennial species.
Prohibit use of invasive species.
Promote crop rotation on cultivated lands.
Encourage soil conservation.
Promote only biofuels that are at least net carbon-neutral.
Garden Microbe Could Guard Against Pathogens
The garden-dwelling microbe Enterobacter asburiae has been found to significantly reduce the levels of the two pathogens Escherichia coli O157:H7 and Salmonella enterica, according to a news release from the U.S. Agricultural Research Service (ARS).
ARS food-safety scientists have been working to find a way to stop these and other foodborne pathogenic bacteria before they can make it to leafy greens and other vegetables people eat uncooked, the press release says.
ARS geneticist Michael B. Cooley began studying the pathogen-fighting abilities of E. asburiae in 2002. He found that when he inoculated the seeds of thale cress with E. asburiae, E. coli, and Salmonella, the levels of the two pathogens dropped.
A follow-up experiment with green leaf lettuce identified an ordinary bacterium, Wausteria paucula, that enhanced the survival of E. coli sixfold. However, when E. asburiae was added to the experiment, the microbe decreased E. coli’s survival twentyfold to thirtyfold, according to ARS.
A 19-month surveillance study conducted in 2006 discovered that E. coli can travel long distances in stream-water and floodwater when strains were discovered in environmental samples. This research showed that conditions may occur in the field that cause contamination of produce.
Cooley also began work on another study in 2005 that will continue through 2010, with the goal of characterizing the ecology of enteric pathogens on produce including E. coli. The study will develop methods for detection of the pathogens and determine factors driving the interaction between the pathogens and bacteria and other elements found on produce.
Cooley’s research points to E. asburiae as the most promising biological control agent to keep salad greens safe for human consumption, according to ARS. Agricultural practices that encourage the growth of competing bacteria, such as E. asburiae, may be the key to reducing the incidence of produce contamination. For more information, see www.ars.usda.gov.