WASHINGTON: A scientific team from the North Carolina State University is working to turn woodchips into a substitute for coal by using a process called torrefaction that is greener, cleaner and more efficient than traditional coal burning.
Environmental organizations have raised concerns for decades about the environmental impact of the burning of fossil fuels - particularly coal - for energy.
The combustion of coal contributes to acid rain and air pollution, and has been connected with global warming.
During torrefaction, woodchips go through a machine - almost like an industrial-sized oven - to remove the moisture and toast the biomass.
The machine, called a torrefier, changes more than just the appearance of the woody biomass. The chips become physically and chemically altered - through heat in a low-oxygen environment - to make them drier and easier to crush.
The torrefied wood is lighter than the original woodchips but retains 80 percent of the original energy content in one-third the weight.
That makes them an ideal feedstock for electric power plants that traditionally use coal to generate energy for businesses and residential neighborhoods.
While the process of torrefaction is nothing new, NC State's particular torrefier machine, called the Autothermic Transportable Torrefaction Machine (ATTM), is field portable and self-heated.
Traditional torrefier machines are bulky and immobile, but the ATTM lends itself to field-based operations, which reduces the cost of transporting tons of woody biomass to and from the combustion facilities.
The ATTM is also largely self-powered, producing a large energy return while also removing carbon from the atmosphere.
"This process could help us build a bridge to more energy independence," said Chris Hopkins, a doctoral student in forestry at NC State and developer of the torrefier machine.
Since the torrefier machine is small enough to transport, it could be set up close to forest-clearing operations, making the process even more efficient.
