Fiber characteristics, pulpability, and bleachability of switchgrass

Increasing concerns for future fiber supplies and potential increases in wo od cost have strengthened the pulp and paper industry's interest in alterna tive pulp fiber sources, i.e., annual plants. Among many of them, switchgra ss(Panicum virgatum), a nauve North American grass, stands put as an excell ent candidate because of tis high crop yield (10-12 metric tons/ha/year), c hemical composition, extractives, and low ash content. To assess the paper-making potential of switchgrass, a systematic study was conducted that examined fiber characteristics, pulpability, bleachability, and physical properties. The fibers were characterized using light and sca nning electron microscopy, a Kajaani fiber optic analyzer, and a Bauer-McNe tt classifier. These technique revealed that the pulp contains (a) a high a mount of fines, (b) fibers with a wide distribution of lengths, and (c) fib ers that are slender with thick walls. The material was easily pulped using the kraft process with acceptable pulp yields, i.e., a 50% total yield wit h a kappa number of 14. The burst, tear, and tensile strengths and freeness were typical of nonwood fibers. The pulp was readily bleached using conven tional (C+DED), elemental chlorine-free (ODEoD), and total chlorine free (O ZEQPo) sequences, giving brightness greater than 85%.