Plants - The Ecology of Building Materials - page 178

(often called potash) is an important ingredient in the production of glass. Today,
it is almost exclusively produced industrially from potassium chloride.

Cellulose

Cellulose can be produced from peat, straw and timber; the majority comes from
timber. The main constituent of timber is cellulose (C 6 H 10 O 5 ) n . Carbon makes up
44 per cent by weight, hydrogen 6.2 per cent and oxygen 49.4 per cent.
In the sulphite chemical process of the paper industry timber is ground and
put under pressure with a solution of calcium hydrogen-sulphite, Ca(HSO 3 ) 2 ,
releasing the lignin. The pure cellulose is washed again and may be bleached to
a clean white pulp, rich in fibre. To produce paper glue and filler substances such
as powdered heavy spar, kaolin or talcum are mixed in. Leaving out glue will
produce more brittle, porous paper.
Viscose, rayon, cellulose acetate, celluloid, cellulose varnish, cellulose glue and
cellulose paste are all produced from cellulose. For the production of viscose, cel-
lulose from spruce timber is best. Other chemicals are often added in these
processes, e.g. acetic acid and methanol (extracted from wood vinegar). Cellulose
acetobutyrate (CAB) and cellulose propionate (CAP) are plastics made by adding
a mixture of acetic acid and butyric acid to cellulose. These materials are as clear
as glass and can be used to produce half-spherical roof lights.
The cellulose industry uses large quantities of water and creates high pollution
levels. The cooling process leaves a high concentration of lye as a by-product.
This contains different organic process chemicals, of which a few are recycled;
the rest is released into rivers or lakes near the factory. These industries could
reduce effluent to a minimum, if not completely, given the appropriate technolo-
gy.
If the cellulose is bleached with chlorine, the pollution increases drastically.
Organic chlorine substances can accumulate in the nutrient chain and act as poi-
sons. Alternatives are bleaching paper with oxygen or hydrogen peroxide, but
ideally all bleaching should be stopped.

References

A NDERSSON A, Lin kommer igjen , Fåra 1986
B UNKHOLT A, Utnyttelse av lauvtrevirke til produk-
sjon av skurlast og høvellast , NLH, Ås 1988
B ROWN L R (ed.), State of the world , Washington 1990
H ALL G S et al , The art of timber drying with solar
kilns , Hannover 1981

R AKNES E, Liming av tre , Universitetsforlaget,

Oslo 1987
T HÖRNQUIST T, Trä och kvalitet , Byggsforsknings-
rådet rapp 77:1990, Stockholm 1990