Cellulose

Cellulose (C6H10O5)n can be produced from peat, straw or timber; the majority comes from timber. By weight cellulose is 44% carbon, 6.2% hydrogen and 49.4% oxygen.

In the sulphite chemical process of the paper industry, timber is ground and cooked under pressure with a solution of calcium hydrogen-sulphite, Ca(HSO3)2, releasing the lignin. The pure cellulose is then washed and often bleached. To produce paper glue and filler substances such as powdered heavy spar, kaolin or talcum are mixed in. Omitting the glue will produce more brittle, porous paper.

Cellulose fibres are often used in insulation materials, either as virgin fibres or recycled. They are also used as reinforcement in cement-based building boards. Paper products are found in many building products, from building boards to wallpapers.

Further processing of cellulose leads to cellulose glue, cellulose varnish, viscose, rayon, etc. Other chemicals are often added in these processes, e.g. acetic acid and methanol. Cellulose acetobu-tyrate (CAB) and cellulose propionate (CAP) are plastics made by processing cellulose with acetic acid and butyric acid. These materials are as clear as glass and can be used to produce roof lights. Cellulose-based plastics are well suited for being mixed with plant fibres into biocomposites (Mohanty etal., 2005).

The cellulose industry consumes large quantities of water and causes high pollution levels. The cooking process leaves a substantial amount of lye as a by-product. This contains different organic

process chemicals, of which a few are recycled; the rest are released into rivers or lakes near the factory. If the cellulose is bleached with chlorine, pollution increases drastically. Organic chlorine substances can accumulate in the nutrient chain with toxic effects. Alternatives are bleaching paper with oxygen or hydrogen peroxide.

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