13 Paper

• Describe what paper is, how it “works”, and how it is made

  • True” paper is made by separating plant fibers (like bast fibers or secondary xylem) and then matting and pressing them into thin sheets.

  • As the paper dries, hydrogen bonds form between cellulose fibrils, holding the fibers together without glue.

  • Individual plant fibers are separated and then matted and pressed while forming hydrogen bonds

• Describe the steps in papermaking from various cellulose fibers

  • Gather and beat the pulp to fray the cellulose fibrils and increase its capacity for hydrogen bonding

  • Suspend fibers in water

  • Drain in a fine wire mesh

• Explain why some fibers are unsuitable for making paper on industrial scales

  • Too short or too brittle fibers can’t form strong hydrogen bonds, resulting in weak paper.

  • Fibers with too much lignin (e.g., unprocessed wood or certain grasses) cause yellowing and degradation.

  • Fibers with resins (common in some conifers) are harder to separate chemically.

  • Non-cellulose fibers (like waxy or oily tissues) are hard to process and can damage equipment.

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• Identify the main reason wood pulp is used for paper

  • Wood is abundant and renewable.

  • Secondary xylem cells (wood fibers) are strong and rich in cellulose.

  • Mechanization of pulping and papermaking makes wood a cheap, large-scale source.

  • Trees grow fast enough to sustain a high-volume industry when managed properly.

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• Distinguish 3 methods for producing wood pulp for papermaking

  • Mechanical Processing: wood is ground into a pulp using physical force but lignin causes it to degrade and yellow

  • Sulfite Processing: wood is treated with aid to dissolve lignin. More energy efficient. Acid residue causes it to brittle. Not good for resinous wood

  • Sulfate Processing: wood is treated with chemicals and dissolves resins, making strong paper that doesn’t degrade. But causes more pollution because of bleaching 

• Identify major environmental concerns with paper, and how they might be alleviated

Environmental concerns:

• Deforestation: 35% of global tree harvest is for paper. 10% of old-growth forests are cut for pulp.

• Waste: Paper makes up ~40% of U.S. garbage.

• Pollution:

  • Bleaching (especially with chlorine) creates toxic byproducts like dioxins.

  • Paper mills also release nitrogen and sulfur oxides → contribute to acid rain and air pollution.

How to alleviate:

• Recycling: Reduces demand for new pulp, though not ideal for high-quality paper.

• Use alternative fibers (e.g., hemp, kenaf, agricultural waste).

• Switch to cleaner processes (e.g., oxygen bleaching instead of chlorine).