Biofuels offer the promise of lower emissions, but they are often made from crops that might otherwise be used for food—or displace food acreage.
Given the scale of production needed for a given biofuel to have a meaningful impact on carbon emissions, that's a problem.
So the challenge for researchers is finding a plant source that isn't needed for food, and can produce as much biofuel as possible from a given amount of acreage.
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One team of researchers now believe that plant could be sugarcane.
Altering sugarcane to produce oil could yield much greater amounts of biodiesel than the current most popular crop, soybeans, say researchers from the University of Illinois (via Wards Auto).
Soybeans yield only about one barrel of biodiesel per acre, which is too little to meet demand, researchers say.
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But they claim a genetically-modified sugarcane plant could produce biodiesel at a much greater rate, and on land considered unsuitable for food crops.
In a best-case scenario, this method could provide enough oil to account for two thirds of the diesel and jet fuel currently used in the U.S., they claim.
All of this is possible, in theory, by altering a plant's metabolism to convert sugars into lipids, or oils, which can be refined into biodiesel.
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The natural makeup of sugarcane is typically only 0.5 percent oil, but the so-called "oil-cane" plants are now at 12 percent oil in the lab.
Researchers hope to reach 20 percent, a figure their most optimistic predictions are based on.
At that rate of production, costs would average $2.20 per gallon, compared to $4.10 for soybean biodiesel, researchers claim.
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In addition to modifying plants to produce more oil, researchers also engineered them for greater cold tolerance and more efficient photosynthesis.
The leftover sugars in these plants can also be made into ethanol, providing a second fuel source, according to the research team.
However, as with all experimental biofuel processes, the real question is whether "oil-cane" can be scaled up to produce biodiesel on a commercial scale.
Viable large-scale production methods have been elusive, preventing the U.S. from meeting ambitious biofuel goals laid out in the 2007 Energy Independence and Security Act over the past decade.