Improving pulp production with raw material changes
Dimmel DR., MacKay JJ., Pullman GS., Althen EM., Sederoff RR.
The ideal raw material for pulp production would be wood with a low content of easily fragmented lignin, a high content of crystalline cellulose, and the presence of pulping catalysts. Tree breeding and genetic manipulation offer ways to achieve these goals and improve the selectivity of pulping. In the area of breeding, there has been considerable interest in a naturally occurring mutant loblolly pine tree that is deficient in cinnamyl alcohol dehydrogenase (CAD). The absence of the CAD enzyme leads to a different pool of precursors for lignin production. The precursors possess fewer sites for polymerization that lead to a less branched, lower molecular weight lignin. In comparison to a normal 12-year-old loblolly pine, wood from a 12-year-old CAD-deficient loblolly pine is much more easily delignified under soda, kraft, and soda/AQ conditions. In the area of genetic manipulation, we are attempting to increase the content of anthraquinone pulping catalysts in hardwoods that already produce low levels of these materials. The strategy used might also lead to trees with less lignin.