Norway is showing how the previously unexploited left-overs from logging can now be used as biofuel.
SINTEF are taking in the waste material and are transforming it into fuel. The GROT (see fact box) is transported to the laboratory in its raw form and is regarded as low-value fuel. But the SINTEF scientists and technicians are transforming it into a valuable source of heat. The fuel can be used in industrial heating furnaces that have previously been fuelled with wood pellets or domestic pellet stoves. The torrefaction of the material can be compared to an extreme sauna for timber and vegetation.
"Cheap fuel, and Norwegian logging sites are full of it. But it is a poor-quality fuel, because it is so variable in composition," says senior scientist at SINTEF, Øyvind Skreiberg.
The torrefaction process allows all the components of the GROT to be mixed together resulting in a steadier burning rate. "This mixture means that the efficiency and characteristics of the combustion process are extremely variable. In the worst case, they can destroy a combustion chamber," says Skreiberg.
Breaking down the fibre
On its way through the highly insulated steel cylinders of the laboratory rig, the raw material has been heated to 275 oC. The heat treatment has broken down the fibrous structure of the biomass. According to Skreiberg, this has two benefits.
"In the first place, the torrefied material can easily be crushed into the powder which can be stirred around to form a homogeneous, and therefore combustion-friendly, mass."
"Secondly, this powder can be pressed into pellets with a high energy content per unit of weight and volume; in other words, it is also a transport- and storage-friendly fuel. Pellets of torrefied biomass can withstand getting wet, just like coal, and are very stable under storage."