Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=198813
Story Retrieval Date: 3/29/2015 2:23:46 AM CST
Photo courtesy of Bio Architecture Lab, Inc.
Could kelp– a type of brown seaweed —fuel your gas tank?
Researchers are bringing us one step closer to this alternative energy source with a process that uses a bacterium commonly found in our gut to metabolize brown algae into ethanol.
The Bio Architecture Lab at the University of California, Berkeley, is using genetically engineered E. coli bacteria to break down difficult-to-digest algae into useable ethanol. A laboratory team reports on the results in this week’s issue of Science magazine.
The program, still in research phases, will be expanding in the near future to study the economic impact of using algae in large-scale ethanol production.
So far, plant-to-ethanol fuel conversion has emphasized land crops, such as corn or sugarcane. But now, researchers hope large-scale conversion of brown algae into ethanol could help meet the demand for sustainable fuels without hiking prices up by competing for food crops.
"Brown algae can be one of the world’s most scalable and environmentally sustainable biomass sources for production of renewable fuels and chemicals for two key reasons," according to Yasuo Yoshikuni, chief science officer for the lab and principal investigator for the biofuels research at Berkeley. "One, it has a high sugar content and, two, seaweed does not compete with food crops for land or water use and large scale aqua farming operations are environmentally benign.”
The scientists altered E. coli genomes to include a large selection of genes that can break down alginate, the complex starch found in brown algae, into smaller sugar compounds.
Once the E. coli degraded the alginate into smaller sugars, the bacteria were able to use their metabolic power to ferment the sugars into ethanol. This process is similar to the fermentation and distillation processes associated with potable alcohols such as vodka or moonshine.
“The engineering is very clever and a 28 percent yield is very good. It means they have a very efficient process,” said Steve Mayfield of the San Diego Center of Algae Biotechnology. The center is following the research.
Because of its relatively high sugar content, the optimum ethanol output per pound of seaweed ends up being approximately two times higher than the output from sugarcane and almost five times higher than output from corn, according to a 2010 U.S. Department of Energy study.
Emphasizing that this alone will not solve the world’s energy crisis, Mayfield mentioned the need to find better ways of harnessing solar power and convert it to chemical energy.
But the algae conversion could address some of the key controversies associated with ethanol as biofuel.
Corn-ethanol production is the focus of the debate, centering around two main points: first, there is not nearly as much energy in ethanol as there is in petroleum products; second, the energy created from corn-ethanol shifts the use of land for fuel rather than other resources like food.
The issue with ethanol compared to gasoline is one of volumetric efficiency as well as energy efficiency, said Michael Wang, a scientist at Argonne National Laboratories near Lemont.
Although ethanol only has two-thirds the amount of energy of gasoline, each unit of ethanol packs a little more punch compared to gasoline because it offers a higher octane fuel even if it isn’t as fuel efficient.
The second prong of the debate questions the actual energy yields from the ethanol-dedicated corn.
“Last year, 40 percent of corn grown in the U.S. was used for ethanol production,” Wang said, which translates to 14 billion gallons of ethanol in 2011.
Compared to gasoline, these 14 billion gallons of ethanol only represent 9.3 billion gallons of gasoline equivalent. So ethanol accounted for an estimated 7 percent of the gasoline used in the U.S., Wang said.
While ethanol is not as energy rich as gasoline, using brown algae to make it still addresses the problems associated with land use.
Despite the success of the conversion process, Mayfield said he remains skeptical about the logistics of transporting brown algae from the ocean to the refining site on a large scale, arguing that the energy associated with harvesting algae would probably be more costly than the ethanol energy created. However, the representative for the Bio Architecture Lab said this is not a problem.
“Industrial seaweed aqua farming has been done for hundreds of years in many places in the world, so scaling up production is not an issue,” said Yoshikuni.
It is not certain whether the actual ethanol energy created from the algae would outweigh the energy consumed in harvesting.
“Not every solution has to solve all of our energy problems, but maybe a hundred little inventions could address our energy problem,” Mayfield said.