Formic acid pulping of crops residues available in Bangladesh

Bangladesh is a densely populated agricultural country. As the allocated forestland for pulpwood production is very limited and a substantial amount of crops residues are generated each year, the latter can substitute pulpwood. But it is hard to use crops residues as pulping raw materials in a conventional pulping process due to its high content of silica and fines. It was observed that formic acid (FA) pulping process can overcome these limitations. In this context, fourteen residues of crops produced in Bangladesh were evaluated by FA pulping with varying FA charge for 4 h at the boiling temperature followed by peroxyformic acid (PFA) treatment under constant conditions. It was observed that pulp yield and delignification degree decreased with FA charge. Also, PFA treatment further reduced the kappa number of pulps. Final pulp yields were 39–51% with the kappa number of 12–28 depending on crops residues. Holocellulose and α-cellulose content in crops residues were positively correlated (R² = 0.95) with pulp yield at 0% level of significance. Pulps were bleached by alkaline peroxide bleaching and brightness reached to about 80% with acceptable papermaking properties.