Fast pyrolysis is a method for converting biomass into three energy rich products: char, gas and bio-oil, where the latter is most interesting.  Pyrolysis is an endothermic process where biomass is heated in an anaerobic environment and, with the right operating conditions, up to 80 %wt bio-oil can be extracted. Key parameters for fast pyrolysis are: stable reactor temperature (~500°C), short residue time for gas in the reactor (<2 s) and a very high heating rate for the biomass. Today there are several different process solutions for fast pyrolysis, where fluidized beds and rotating cones are most developed. Bio-oil has compared to fossil oil: lower heating value, low pH and also polymerizes with time. Because of this upgrading is desirable for increasing competitiveness. Several large projects for producing of bio-oil are at the moment developed around the world. Though often is subsidy money involved in these projects.  Domsjö Fabriker AB in Örnsköldsvik, who is converting softwood into special cellulose, bio-ethanol and lignin, are interested in pyrolysis technology. They are using the unique sulphide process; and during the pulping of the biomass a residue in form of knots are extracted from the process. This waste product is of little value and the company is interested in investigating the possibility to produces bio-oil from these knots. The knots have several characteristics that differ from normal biomass, such as high amount of ash and extractives. High ash content leads to secondary reactions in the reactor, which leads to lower yields of bio-oil. Because of this the knots are not an optimum raw material for fast pyrolysis. At the same time high amount of extractives in the biomass might result in a to two phase liquid product. To ensure how well the knots will behave during pyrolysis testing is needed. The relatively low reject flow (18 tons/day) will, in relative terms, lead to high investment costs and a larger facility (120+ tons/day) is preferred in order to keep production costs low. Considering this, plus an uncertainty regarding the knots as a raw material for pyrolysis, bio-oil as a fuel and fast pyrolysis competitiveness, a recommendation for investing in a pyrolysis plant at Domsjö will not be recommended without first experimentally examining this untested biomass in combination with fast pyrolysis technology.