Mechnical pulping gives higher yields and is cheap, but the quality of paper produced is relatively poor, turning yellow on exposure to sunlight. Further, the mechanical pulping requires lot of electrical energy. These difficulties can be overcome through the use of biotechnology.
The chemical pulp is also subjected to bleaching, in order to remove residual lignin leading to satisfactory increase in the brightness of paper. This bleaching step creates numerous toxic derivatives of lignin that constitutes environment hazard.
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