Harvesting Machine Driving Mesquite-to-Ethanol Potential

That will change with a new mesquite harvester for use in wood-to-ethanol production, said Dr. Jim Ansley, Experiment Station rangeland ecologist.

The only one of these machines in existence was demonstrated at the 2006 Range and Wildlife Field Day on Oct. 5 in Vernon.

But Ansley said it won't be the only one for long with commercial production expected soon.

A combination of the U.S.'s dependency on foreign oil and a growing problem for producers with brush encroachment, which reduces grasses and production and water availability, has driven his recent work.

“We're emphasizing mesquite and we're targeting ethanol conversion, although there are other bioconversions that could take place,” Ansley said.

He said there are an estimated 51 million acres of mesquite in Texas, with 30 million acres of moderate to dense mesquite in Central Texas.

Mesquite is drought hardy, fixes its own nitrogen, requires no seeding, fertilization or irrigation, resprouts vigorously after topkill and grows on dry, nutrient-poor soils, he said. Finding a profitable use for it is a win-win situation.

For the past year and a half, Ansley has been working with private industry to build the harvester prototype. The prototype is owned by the Experiment Station and a joint patent is pending, Ansley said.

The patent and commercial production will be carried through Brush Unlimited and Richard Frailey of Altus, Okla. Ansley said he and Frailey already have been contacted by several people in Texas, New Mexico and Oklahoma who have expressed interest in buying the machines. No commercial price has been established.

A conventional brush-cutting machine such as the Barko 775C or HydroAxe is used to fell or rough cut the trees. These brush cutters have a large rotor in front with what are called hammers on it to knock down the brush.

The new harvesting machine is not self-powered and is pulled through the felled trees with the HydroAxe, Ansley said. It is powered by the HydroAxe with a hydraulic system. With another rotor and more hammers, the felled wood is further broken up and then sucked up a chute and into a hydraulically hinged bin.

From there, the wood can be dumped into trucks and hauled to an ethanol plant, where it would be further ground into a sawdust and entered into the ethanol-production system, he said.

“The Experiment Station didn't have a brush-cutting machine, so that is why we went to cooperative efforts with private industry,” he said. “It has taken the involvement of many people to make this happen and represents a good example of university researchers and the private sector working together.”

The initial vision for a mesquite harvester was that of Montey Sneed with Texas Ethanol Company of Vernon and Ansley's, he said. Frailey was brought in, along with Larry and John Willis of W.W. Welding in Altus, Okla., to help design and build the machine.

The final step was finding an end market. That involved Pearson BioEnergy Inc. in Aberdeen, Miss., a company that has been developing a process, not yet commercially available, for converting wood to ethanol.

Funding for the project has been provided by a grant from the DOE-State Energy Conservation Office, along with funding from Pearson BioEnergy and the Experiment Station.

Ansley also recently began working with Cameron University in Lawton, Okla., which received a grant from the state of Oklahoma to look at mesquite as an alternative fuel in southwestern Oklahoma.

“To develop this industry, there are supply, harvest, conversion and ecological issues,” Ansley said. “Here, we're looking at cutting, collecting, baling and transporting the mesquite feedstock.”

The new machine was designed for a commercial-size ethanol plant, with the capability to harvest 5 to 10 acres a day, Ansley said, but it doesn't have to be limited to mesquite harvest.

A smaller version could be used for roadside cleanup or a producer may want to use it as a shredder and a way to remove the debris and thorns from the pasture, he said.

Mesquite is not totally removed, so regrowth will occur, Ansley said. That is important to the mesquite-to-ethanol program. He estimates that in North Texas, at least 10 years of regrowth is needed before mesquite can be harvested again.

His studies show each 10- to 12-year-old regrowth tree has about100 to 120 pounds of wood. Thus, an estimated 300 trees per acre would produce about 30,000 pounds or 15 tons per acre.

The concept of harvesting mesquite as a biofuel has been around since the 1970s, Ansley said. There have been unsuccessful attempts in the past to build machines designed to cut and collect the mesquite all in one machine.

“Our theory is that is too much for one machine to do,” he said.