Life Cycle of Materials 26 26.1 Materials in common use
The most commonly used materials are paper, cardboard, plastic and metals. Paper and cardboard are obtained from wood. Metals are obtained from rocks, for example copper ore, and plastic is obtained from crude oil.
Extraction Before materials are processed and converted into more useful forms they are called raw materials. While extraction methods are different for each raw material, most methods have a significant impact on the environment. Figs. 1 and 2 show some of the impacts of harvesting timber and mining for metals.
Fig. 1 Deforestation.
Wood Wood is used for building and making furniture, paper and cardboard. Wood is obtained by harvesting forests. Clear cutting is the most economical method. This involves cutting all trees from an area using heavy machinery. Clear cutting can damage the environment in many ways. The heavy machinery can physically damage the soil. Without the protection of the trees, rain can wash away the fertile topsoil. The roots of living trees help to keep the soil stable. Clear cutting on hillsides can destabilise the soil. This increases the risk of landslides and flooding. Clear cutting also has a significant impact on the landscape. Cutting down large areas of forest contributes to global warming because trees are carbon sinks. They absorb CO2
during photosynthesis, taking it out of the atmosphere. 285
Fig. 2 An open-cast iron mine.
Fig. 3 Heavy machinery used for clear cutting can damage the soil.
