Question

Tree - free pulp can be made from agricultural wastes​

Answer 1

Answer:

Tree-free paper or tree-free newsprint described an alternative to wood-pulp paper by its raw material composition. It is claimed to be more eco-friendly considering the product's entire life cycle.

Sources of fiber for tree-free paper[1] include:[2]

agricultural residues (e.g. sugarcane bagasse, husks and straw)

fiber crops and wild plants, such as bamboo, kenaf, hemp, jute, and flax

textiles and cordage wastes

Non-fibre sources include:

calcium carbonate bound by a non-toxic high-density polyethylene resin

Answer 2

Answer:

This method implies mechanical destruction of lignin which glue the fibers and hold them together. The

most widely used mechanical method is the stone ground wood method. This method involves the wet grinding

of wood into a fibrous mass by means of a large revolving grinding stone. Logs of wood are hold with pressure

against the surface of the stone. A stream of water is sprayed on the stone to carry the pulp away. Ground wood

pulp contains practically all the lignin of the original wood. The yield is about 95 % of the original wood. The

ground wood pulp contains individual fibers, broken fibers, fines and coarse fiber bundles. The disadvantage of

ground wood pulping is that grinding weakens the fiber and that lignin is not removed. Ground wood pulp

fibers are not as strong as their chemically lignin free counterparts. But the great advantage is the high yield and

low cost.

This pulp is used mainly for newsprint where cheapness is necessary. A disadvantage is the presence of  the whole lignin in the pulp. This causes yellowing of the paper after short time. Yellowing is however allowed

in newsprint since the newspaper is dispensed with, after a short time.

Generally speaking, pulps from agricultural wastes, even semichemical pulps are easily bleachable.

This is due to the lower lignin content in these pulps compared to wood pulps and to their open fibrous

structure. Such pulps require less chlorine than wood pulps. Bleaching with chlorine and hypochlorite takes

place at normal pressure and at temperatures varying from 20 to 40 ºC.