AbstractA 500 L biomass fast pyrolysis Auger reactor was designed, constructed and experimented with biomass of Mesquite ( Prosopsis juliflora) and rice straw (Oryza sativa). The thermogravimetric analysis of feed stock and the physico chemical properties of the feed and product bio-crude was done as per ASTM standard. An optimization based on Response Surface Methodology was carried out for the operating parameters chosen as: (1) reactor temperature, (2) feedstock-heat carrier ratio and (3) rotational speed of the auger reactor. The optimum bio-crude yield of 42.6 wt.% was observed at 500 °C, feedstock-heat carrier ratio 1:2 and 30 rpm for mesquite sawdust and 34.6 wt.% at 475 °C, 1:2 ratio and 50 rpm for rice straw. Among the two kinds of feedstock tested, the sawdust yielded better product under identical operating conditions. The final bio-crude have properties similar to the results that was reported in the past and has HHV- higher heating value less than petroleum fuel.