If you have heard the word "torrefaction," you probably heard it in connection with your cup of coffee, especially since coffee roaster La Colombe Torrefaction hooked up with celebrities to spread their name.
Torrefaction technically refers to a roasting process in which biomass is heated, or pyrolyzed, in an oxygen-free environment. The process increases the energy density of the biomass by removing volatiles and breaking down the complex molecules to simpler ones in which the carbon energy is more easily used.
Torrefaction is the new kid on the energy block. It has been only half a decade since scientists first proposed that roasting biofuel like coffee beans could boost energy yield. But now torrefaction is poised to burst onto the renewable energy scene.
Torrefaction provides significant benefits relative to using biomass that has not been slow roasted. The extremely dry pellets reduce the costs (and environmental footprint) of shipping biomass fuels. The higher energy density makes it possible to co-feed the biomass in plants designed for the higher energy content of coal. And perhaps most importantly, the process makes the biomass resistant to absorbing rainwater, which means that power plant operators can store the material outside without ruining the feedstock or stinking up the neighborhood.
The world's largest torrefaction plant, run by Topell Energy in the Netherlands, recently announced successful 'proof of concept' tests for co-feeding biopellets generated using the torrefaction process (pdf).
Recent research focusing on the life cycle footprint of torrefaction and on the availability of biomass which does not compete with food has also opened doors for the young companies trying to expand in this field, as findings suggest that with proper siting decisions and plant design, the input of heat energy required for roasting biomass makes sense.
So next time you are sipping your cup of coffee at the internet cafe, try googling "torrefaction." The new kid on the block would like to get to know you.