The University of Arizona has developed a unique method of pumping concentrated, viscous biomass slurries, characteristic in biomass direct liquefaction systems. A modified single-screw extruder has now been shown to be capable of pumping solid slurries as high as 60 wt. % wood flour in wood oil derived vacuum bottoms, as compared to only 10-20 wt. % wood flour in wood oil in conventional systems. A Phase II program has integrated the extruder-feeder pumping system with a unique reactor which offers potential for further improving direct biomass liquefaction technology. An experimental facility was constructed during 1983-84, and shakedown operations were successfully completed in early 1985.