Kudzu and You

Posted on June 16, 2008

As concerns rise over corn ethanol creating competition between food and fuels, ethanol made from one of the country’s most invasive plants — kudzu — could be part of the solution.The kudzu vine, also known as “the plant that ate the South,” was brought from the Far East to the US in the 1800’s. Originally intended to help with erosion, it was found to have a mind of its own. Most people see it as a green monster as its vines can grow more than the height of a man in a week. Its starchy roots go deep into the soil, and just a fragment of the plant remaining in the ground is enough to allow it to come back next season.

Researchers gathered samples of kudzu from different locations in the south at different times of year and measured the amount of carbohydrate — which can be converted into ethanol by yeast — present in leaves, vines and roots.

The roots were by far the largest source of carbohydrate in the plant: up to 68 percent carbohydrate by dry weight, compared to a few percent in leaves and vines.

The researchers estimate that kudzu could produce 2.2 to 5.3 tons of carbohydrate per acre in much of the South, or about 270 gallons per acre of ethanol, which is comparable to the yield for corn of 210 to 320 gallons per acre.

Crucial to making the plan work would be figuring out whether kudzu could be economically harvested, especially the roots, which can be thick and grow more than six feet deep. To balance this expense the plant requires zero planting, fertilizer or irrigation costs. For sure, Kudzu meets these criteria as I don’t know anybody in my lifetime that has planted, watered, or fertilized any of the stuff.

Even if equipment could harvest the roots, a large fraction of kudzu vines blanket steep hillsides and would be difficult to access. The team estimated that about one-third of kudzu plants would be harvestable. If so, they calculate that kudzu could offer about 8 percent of the US bioethanol supply.

A gentle reminder is also in order at this juncture. Ultimately, ethanol is not the answer to our energy addiction. Automobiles can never run any product that is a replacement for gasoline and do so in an efficient way. All the known products require expensive processes to make them ready for an internal combustion engine (ICE). We simply have to produce alternative power, which also means moving away from our current types of engines. So whether we go to magnetic, electric, solar, or whatever, it has to be something besides an ICE engine.