Researchers at UCLA have opened a path to cheaper and cleaner biofuels by using genetic engineering to fundamentally change how certain organisms process sugar.
Conventional biofuels are either too expensive to compete with fossil fuels or they release so much carbon dioxide that they’re hardly worth making—or both.
The UCLA advance, which increases the amount of biofuel that can be made from sugar by 50 percent, could make it cheaper to produce biofuels from a variety of sources, especially biomass such as wood chips and grass. The U.S. biofuels industry is in desperate need of such advances—even though Congress has mandated that a certain amount of biofuel from biomass be blended with gasoline, high costs and other factors have limited production, leading the EPA to repeatedly waive the requirement.
The UCLA work is a “promising advance in biofuels technology,” says Wade Robey, chief technology officer at the ethanol producer POET. He says it shows the potential of advanced genetic engineering “to drastically reduce both greenhouse gas emissions and the amount of corn or biomass used to produce a gallon of biofuel.”
In conventional biofuels production, sugar derived from sources such as corn and biomass is fed to yeast, which ferments it to produce ethanol. But the fermentation process wastes a third of the carbon atoms that make up sugar; rather than being used to make ethanol, the carbon is released in the form of carbon dioxide.
The UCLA researchers cobbled together genes from a variety of organisms to create an alternate way to process sugar that doesn’t emit any carbon dioxide, and uses all of the carbon in sugar to make biofuel. They created genetically modified E. coli bacteria to demonstrate the process, but they say the same genetic pathway could be incorporated into other organisms, including yeast.
“Anytime you use fermentation, you lose one-third of the carbon to carbon dioxide. We can retain that carbon, reduce the carbon footprint of ethanol production, and make more money,” says James Liao, professor of chemical and biomolecular engineering at UCLA.
In order to use all of the carbon in sugar, it’s necessary to add hydrogen to the process. The source of that hydrogen and its cost relative to the cost of sugar determine both the total carbon emissions and the cost savings. Using hydrogen from natural gas is the cheapest option. But getting hydrogen from natural gas also releases carbon dioxide, offsetting some of the carbon dioxide savings of the new process. In this case, emissions from the production of ethanol would be reduced by about 50 percent. Using hydrogen made by splitting water with solar power would eliminate all of the carbon dioxide emitted during fermentation, but the cost would likely be too high for the process to be economical.
Since the new approach produces more ethanol from sugar, less land would be needed to produce corn or biomass. And that would reduce carbon dioxide emissions involved in farming (such as from clearing land and using diesel to power farm equipment).
The biggest cost savings will be for cellulosic ethanol derived from biomass. Sugar from cellulosic sources is much more expensive than sugar from corn or sugarcane, so there are greater benefits to getting more biofuel out of that sugar.
Researchers still need to demonstrate that it’s possible to grow organisms with the genetic changes at a large enough scale to produce commercial biofuels.
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