There is disclosed a method for recovering a low sodium content lignin from spent kraft cooking liquor without the use a of strong mineral acid for acidulation comprising the steps of acidulating a spent kraft cooking liquor with carbon dioxide gas to a pH below about 10.5, precipitating at least a portion of the lignin forming lignin agglomerates and lignin particles in the spent kraft cooking liquor and recovering a low water and low sodium content lignin product comprising calcium or magnesium compounds bound to said lignin.