Civil Engineering Reference
In-Depth Information
Table 10.3:
Primary energy required
for basic plant materials
Material
MJ/kg
Split logs:
air dried
0.5
artificially dried
1.9
Planed timber:
air dried
1.0
artificially dried
3.8
Sawdust/wood shavings
0.6
Straw bales
0.2
Cardboard and paper
9.3
qualities useful to ecological building. They have a strong resistance to rot and can there-
fore be used in very exposed situations without impregnation. Despite this, using rain
forest timber should be avoided altogether, except where the timber is managed under
sustainable and well organized forestry.
The production of organic, plant-based building materials is mainly local or
regional. Energy consumption for industrial processing and transport are rela-
tively low as well as pollution occurs at the cultivating, harvesting and refining
stages. This favourable environmental profile will be reflected in the building, in
the form of a positive indoor climate. When the building starts deteriorating, the
organic materials will return simply and quite quickly back into the natural envi-
ronment. Some of the materials can be recycled for re-use or as a source of ener-
gy. Building materials based on plants act as a store for carbon, thus reducing the
greenhouse effect. One kilogram of dry timber contains about 50 per cent carbon,
which in turn binds 1.8 kg of carbon dioxide). In an average-sized timber
dwelling, which contains about 20 tons of timber, there are 36 tons of carbon
dioxide effectively bound in. The products must be durable and preferably recy-
clable. Carbon is bound within the timber until it rots or is burned.
Table 10.4:
Potential pollution by basic plant materials
Material
Potential pollution by processing
Cellulose
Lye of organic chemicals, e.g. organic chlorine
Solvents
Alcohol, terpenes
Tar
Aromatic and aliphatic hydrocarbons
Plant fibres
Dust
