Abstract: Under ordinary pressure, the methods of Kraft cooking, bisulfite cooking and organic solvents cooking were compared for the effects of separating lignin in Populus alba L.. The experiments were carried out by orthogonal design, the results indicated: the removing yield of lignin from the saw dust of P.alba was 55.8% for the Kraft cooking, 47.3% for the bisulfite cooking, and 83.3% for organic solvents cooking. It showed that organic solvents cooking process performed the best effect of separating lignin, and the residue yield of lignin was the lowest in the solid phase extracts, only 6.3%. Distilling the waste liquid, lignin could be obtained, the yield of which reached to 82.11% of the content of lignin in the raw material, and the recovery yield of lignin arrived 98.75%. Organic solvents could be recovered and recycled.

Key words: biomass, lignin, Populus alba L.