The concentration method was developed for improving the storage stability of pyrolysis liquids without significantly decreasing the flash point of the liquid. This method, by which most of the water and part of the light reactive volatiles of fast pyrolysis liquid are replaced by alcohol, proved in laboratory-scale experiments to possess excellent potential to produce a high-quality (homogeneous, viscosity similar to light fuel oil, stable) liquid product, remove the unpleasant odor of pyrolysis, remove a part of the acidic content, and increase the heating value of the liquid by removing water. Preliminary tests at our companies' process development unit PDU-scale pyrolyser (20 kg/h) showed that similar product upgrading could also be achieved on a larger scale. The kinds of compounds removed were similar. The condenser temperature was optimized to 50 +/- 4 degrees C. Within these conditions, up to 23 wt % of the feed and pyrolysis water can be eliminated from the condensers. This fraction, which can contain up to 9 wt % of the organic yield, can be used for process heat. An overall liquid recovery of 44.3 wt % (compared to typical 48.9 wt %) and a pyrolysis water yield of 9.9 wt % (compared to typical 12 wt %) were measured for dry forest-residue feedstock.