Bio-Coal from Wood Torrefaction


     You may be wondering what the heck ‘torrefaction’ is. For one it is a developing green energy process that requires only transportation fuel to truck it around. This new biomass energy from renewable and sustainable Paulownia tree fuel plantations shows great promise in reducing the CO2 emissions from coal burning power plants. When wood is ‘torrefied’ it possesses altered properties that are almost as energy dense as the coal is. The forestry department at North Carolina State University is working to commercialize torrefied wood which they have affectionately named Carolina Coal.

     This is not really new green technology; the process was developed during the 1930’s and 1940’s. The torrefaction process does not require a building and could conceivably be done at the harvest site to reduce the cost of transporting the finished torrified fuel. The advantage of the portability means that more bioenergy fuel can be transported per load on the road to the energy plant destination. By using Paulownia trees as a preferred source of this biomass energy fuel, the cost of energy production is reduced even further.

     Torrefaction is a process that involves removing water content, cellulose sugars and other volatile organic compounds from the wood chips feed into the processing chamber. The torrefaction machine passes the chips through heated chambers and separates the solids from the liquid and gas forms it holds. The liquefied extraction from the green wood chips creates a form of ethanol, which in turn, fuels the torrefaction machine. The processed and blackened remains of the wood chips look a great deal like splintered coal and have been altered to contain more energy in BTUs than most other forms of biomass energy fuels. Torrefied wood is very lightweight and crushable, allowing for far more mass per truckload.

     Currently, the process is being done with waste wood chips. This will quickly become an issue as there is only so much waste wood available. Currently, this is a huge issue with wood fired power plants in northern states such as Michigan. Power plants need an unlimited source for energy to keep the electrical currents flowing. Paulownia trees present the perfect source of wood chips for a constantly renewing and sustainable biomass source for torrefaction power production. If we aren’t growing the wood needed to keep such a biomass energy system in constant and plentiful supply, our forests could be in danger of further depeletion.

     Paulownia grows extremely fast providing excellent harvest weight in as little as 5 years. Unlike other contenders for biomass energy from short rotation tree crops, Paulownia regenerates an entire new crop without the need to clear thousands of acres of stumps to replant. Additionally, the subsequent harvest from already mature root systems will generate gigantic trees far faster than the first crop harvested. Willow and poplar as short rotation crops will always have to re-establish mature root systems before the new crop can reach a stage of economical harvest for biomass energy fuels.

     In the areas of the country that Paulownia fuel plantations thrive (zone 6 and warmer) this is a far better short rotation tree crop for all forms of biomass energy sources. Willow and poplar are only renewable, they are not sustainable. For the least expensive form of more rapidly renewed torrefied wood for power plant energy, Paulownia trees are the best choice throughout the southern states.