North Carolina State University develops experimental biomass harvester

Forestry engineers from North Carolina State University (NCSU) are developing an experimental biomass harvester that sucks up and pulverizes woody undergrowth and trunks from forest floors. The biomass can then be used for the production of cellulosic biofuels or as a feedstock for biomass power plants. Several similar machines are under development elsewhere, with a first one in Finland already being commercialised; it provides wood chips on the spot, for the emerging forest-based bioenergy sector (previous post).

A prototype of the new machine being developed by NCSU had its first public demonstration in woods east of New Bern, North Carolina, where it gobbled trees in the forest off County Line Road. The event was attended by the gamut of public and private forest-related industries and service in the state.

The harvester works as follows:

• the 56,000-pound machine is pushed by a tractor on treads; it boasts a 440-horsepower engine, making it a quite powerful tool
• despite its weight, the machine produces ground pressure of only 7.1 pounds per square foot, so it moves easily over soft forest bed and pocosin.
  
• the harvester cuts a trail after which its carbide teeth pulverize everything in its six-foot path
• a belt-driven vacuum sucks the ground-up cuttings through an extended chute over the cab and into an agricultural silage wagon hitched to the tractor
• the pulverised biomass is then ready to be utilized as an energy source
• the machine can now harvest between two and four tons of forest bulk an hour
  
• to break even when the biomass is sold as a low-cost feedstock for electricity production at a biomass plant, it would have to double its current output; cellulosic biofuels offer a more promising market
  

The experimental biomass harvester may be four or five years away from profitable use but offers real promise for renewable energy, said Joseph Roise, professor of forestry and operations research at NCSU’s College of Natural Resources:
energy :: sustainability :: biomass :: bioenergy :: biofuels :: cellulose :: harvesting equipment :: efficiency :: forestry :: fire prevention ::

The machine is being developed by NCSU engineers in cooperation with Tim Tabak, a forestry management consultant, for Fecon Inc., manufacturer of the heavy equipment and attachments including Bull Hog commercial mulchers.

The new harvester allows more of the forest’s organic products — bushes, leaves and needles, and trees under 6 inches in diameter — to be used for biomass based biofuels such as Fischer-Tropsch diesel and cellulosic ethanol in addition to its present market in steam-generated electric production, Roise said. When perfected, it is expected to be used mostly for plantation thinning in tree farming, for clearing between the rows, and for forest management, he added.

Roise has been working since the summer with Tabak and NCSU Forestry graduate students Lindsay Hannum and Glen Catts to correct design flaws. Tabak said, that they have to sharpen the teeth during clearing, and that changing the teeth is a challenge. Without air wrenches it took up to 2 hours.

But Roise said the work thus far has produced results much better than they ever thought. A representative for Fecor, Bill Causey of Pittsboro, said the machine offers 'an exciting deal' if you can get it to work. The machine can now harvest between two and four tons of forest bulk an hour. But it needs to be able to harvest about 10 tons an hour to break even on the money it can make selling the harvest for fuel to Craven Wood Energy for steam-generated electricity.

Croatan National Forest District Ranger Lauren Hillman sees potential for forest management in fire prevention and habitat preservation or restoration. Camp Lejeune’s efforts to restore habitat for red-cockaded woodpeckers might be able helped by the machine, said Danny Marshburn, base forest manager. John Duff of Rankin Timber Company in New Bern said, it will be a useful tool on a lot of forest land that is tough to manage.

Its real profitability, however, lies in harvesting brush for next generation biofuels. Its advantage for that use is that it blows underbrush upward without picking up the dirt. The product saved from just being mulch on the forest floor contains the necessary chemical compounds for the manufacture of liquid fuels, Roise and fellow NCSU professor Dennis Hazel said. The professors are already debating which element of the biomass grabbed by the harvester will make it pay off first.

Picture: NCSU Forestry professor Joseph Roise is dwarfed by the 56,000-pound biomass harvester. Credit: Sue Book/Sun Journal.

References:
Sun Journal: Prototype biomass harvester devours small trees, underbrush - December 19, 2007.

Biopact: Efficient timber harvester delivers wood chips on the spot, improves biomass logistics - August 19, 2007