March 16, 2009

Machine makes wood chips a coal substitute

North Carolina State University scientists say they've created a machine that turns wood chips into a coal substitute by using a process called torrefaction.

Environmentalists have long been concerned about the environmental impact of burning of fossil fuels -- especially coal. The combustion of coal contributes to acid rain and air pollution and has been connected with global warming.

During torrefaction, wood chips go through a machine that removes moisture and toasts the biomass. The machine, called a torrefier, uses heat in a low-oxygen environment to make the wood chips both drier and easier to crush.

Although the torrefied wood is lighter than the original wood chips, researchers said it retains 80 percent of the original energy content in one-third the weight.

This process could help us build a bridge to more energy independence, said Chris Hopkins, a doctoral student in forestry and the developer of the torrefier machine.