Science in the Triangle

Like many farmers, Ted Sherrod double-crops, growing canola in the winter on the same land where he harvested sunflowers or safflower grown during the summer. But Sherrod’s “farms” are stretches of roadside or median across the state, and his crops are part of an innovative experiment designed to produce biodiesel for N.C. Department of Transportation vehicles.

Biofuel crops on a roadside near Raleigh. Photo: NCDOT

Sherrod heads NCDOT’s Roadside Environmental Unit, which is charged with keeping the state’s medians and roadsides safe and aesthetically pleasing. The unit is responsible for mowing, stormwater and erosion control, and the 25-year-old wildflower program. While many states have similar wildflower plantings, only two—North Carolina and Utah—have begun exploiting the potential of roadsides as a source of fuel.

The roadside biofuel project aims to answer two questions: whether it is feasible to grow biofuel crops on the state’s roadsides, where soil tends to be poor and compacted, and whether it is feasible to do so cost-effectively. Already, the first question has been answered. This year, Dr. Matthew Veal of N.C. State University extracted more than 100 gallons of canola oil from plants grown on four one-acre pilot sites across the state. This was mixed with conventional diesel to create what is known as B20, a blend of 20 percent biofuel and 80 percent conventional. Sherrod says that this mixture is used because diesel engines do not have to be modified in order to use it.

Canola being harvested from a pilot plot in June 2010. Photo: NCDOT

Canola seeds ready for extraction into biodiesel. Photo: NCDOT

Whether biofuel can be produced cost-effectively is the more challenging question. The initial pilot project was designed to test different subclimates and tillage regimes. But Sherrod says that farming small, disparately located plots is about as efficient as running to four different supermarkets across a county to shop the sales. They are now looking to scale up with larger plots that will allow them to farm more efficiently; at that point they can compare certain fixed costs. “We know what it costs to mow a mile,” he says. Now they would like to know what it costs to till, plant, and harvest a mile of crops.

As Sherrod points out, one way or another, large machines are going to be servicing these roadsides. “Our objective,” he says, “is for dollars of mowing to be reallocated to energy.” The same amount of money might be spent, but it would produce a tangible benefit in the form of biodiesel.

Knowing that corn-based ethanol has gotten a bit of a black eye in the renewable energy community in recent years, I asked Veal to talk me through the difference between ethanol and biodiesel. One argument against ethanol is characterized as “food versus fuel”: ethanol production would take large amounts of acreage currently used for food crops. The roadside biofuel program, though, would be using marginal lands, not North Carolina’s rich agricultural fields. (As an aside, Veal suggests that a largescale roadside biofuel program might also provide jobs for farmers.)

Another problem with ethanol is that of embedded energy—the amount of fuel that is used to plant, vertilize, harvest, and distill the product. Veal says that creating biodiesel is less energy-intensive than creating ethanol, because rather than using heat for distillation, the final product is created through a chemical reaction that requires less input of energy.

Canola oil being extracted from seeds. A simple chemical process will transform it into biodiesel that will be used in the NC Department of Transportation fleet. Photo: NCDOT

He uses a screw press to extract oil from the seeds once they are harvested, then mixes in some chemicals. In 24 hours, the oil has separated into biodiesel and glycerin that is reserved for other uses. Because heat is not used to create the product, very little energy is expended in its manufacture, compared to ethanol.

Veal brought the roadside biofuel idea to Sherrod after learning about Utah’s endeavor in a workshop. It has both state and federal funding and feeds into North Carolina’s renewable energy mandate. Surprisingly, other states are not so far following suit. “We’ve left all the other states in the dust,” says Sherrod.

More information on North Carolina’s roadside biodiesel project will be presented Thursday at a workshop sponsored by Triangle J Council of Governments at RTP Headquarters.