From Campfire To Gas Tank, Mesquite Energy May Be Harvested For Ethanol

Dr. Jim Ansley, Experiment Station rangeland researcher at Vernon, is determining the feasibility of developing a bio-energy industry in rural West Central Texas. The industry would be based on the harvest and use of rangeland woody plants, such as mesquite and red berry juniper, as an energy source.

"We've had so much more interest in this since gas prices went up last summer," Ansley said. "That's going to be a real driving variable. If gas prices continue to go up, I think we could very well see a first generation refinery built in Texas to handle mesquite within five years."

The vision is to build as many as 400 refineries around the state based on mesquite wood. If other woods are considered, the number could go as high as 1,000, he said.

Working with an Aberdeen, Miss. company, Ansley is studying the supply, harvest technologies, ethanol conversion rates and ecological effects of mesquite-to-ethanol production.

One ton of mesquite wood will yield about 200 gallons of ethanol, he said. An acre of the densely populated mesquite standing 10 to 12 feet tall will yield about 8 to 10 tons of wood.

A commercial refinery producing 5 million gallons of ethanol per year will require about 30,000 acres to sustain it, an approximate four- to five-mile radius if the refinery is located near the middle of the mesquite stand, Ansley said.

"The thing that will make this fail is if people think a bigger refinery in the big cities is better," he said. "That's where it will fail. The transport costs to get the feedstock to the refinery will kill you."

Building smaller refineries in the rural regions where the mesquite is located is the key to making this work, he said. Each refinery would support about 30 jobs and enhance rural economies.

"One aspect of mesquite that makes it an attractive renewable fuel is once the above ground growth has been harvested, it sprouts back pretty vigorously," Ansley said. "We're looking at how long it takes before it can be economically harvested again."

A State Energy Conservation Office grant has allowed his team to study harvest of different regrowth rates, as well as develop a mechanized system of harvesting mesquite.

Working with private cooperators, Ansley has helped design a harvester that is in the patent-pending stages. He hopes to have it ready for demonstration at an Oct. 5 field day at the Vernon station.

"We've run some trials with it and we think we have a technique that is workable for gathering this mesquite wood," he said. "That has not been done before."

Ranchers have long been looking for a way to utilize the mesquite growing wild on their pasturelands, but until now, nothing has looked economical, Ansley said.

Mesquite could be used in a wood-fired power plant, but "we think there's much greater potential with ethanol."

A patented process to convert the wood into ethanol is being tested in a prototype plant in Mississippi, Ansley said.

In Texas, the prime area to harvest mesquite is the middle third of the state: a band bordered on the west by a line from Childress to Del Rio and on the east from Decatur to Austin.

"We're talking small travel distance from wood source to these refineries, about 4 to 5 miles," Ansley said. "They would process about 5 million gallons per year of ethanol, which would require about 30,000 acres. Only about 10 percent would be harvested each year, with about 10 years needed for regrowth."

Livestock and wildlife operations should co-exist with a harvest area and be improved with enhanced grass growth and patterned harvest of mesquite, he said.

"The economics are good now," Ansley said. "It just looks tremendously profitable to me today."

The largest expense – building a refinery – is expected to be about $8 million with a profitability of $2 million a year after expenses, he said.

"We're in the process of trying to measure how much energy it takes to harvest mesquite in the field," Ansley said. "That's probably our least researched area. Now that we have this machine constructed, we can start working on that."

Researchers will study different sizes and densities of mesquite and look at the time needed to harvest and the fuel used by the machinery and factor that into the total cost per acre.

"Right now we're estimating $300 per acre, but even if the cost was three times that, we'd still show a profit," Ansley said. "Honestly, I don't know why we haven't done this already, when I look at the numbers."

More information on the mesquite-to-ethanol plan can be found at http://vernon.tamu.edu/brush.