28. Material ﬂows due to mining and urbanization Ian Douglas and Nigel Lawson Mining and urbanization involve the greatest transformations of the landscape through human activity. Mining may leave huge pits and waste heaps, while urban areas contain large stocks of materials brought in from other places. Minerals extraction is broadly divided into three basic methods: open-pit or surface, underground and solution mining. Open workings are the dominant form of extraction of the main commodities mined or quarried: coal and aggregates. Surface, or open-pit, mining requires rock, soil and vegetation removal to reach mineral deposits. The waste rock, or overburden, is piled near the mine. The workings have large energy requirements and produce emissions to the atmosphere and discharges to nearby water bodies. For any particular mine, these hidden ﬂows are often greater in magnitude than the mass of mineral or ore extracted for processing. Urban use of materials involves two broad strands of inputs, stocks and outputs. The buildings and infrastructure of the city can be described as the ‘urban fabric’ (Douglas 1983) while the materials (largely food) consumed by the people and all other organisms within the city can be seen as passing through the urban biosphere. The biospheric use of materials has a rapid turnover, expressed by the high proportion of food waste and packaging in the domestic waste stream. The biospheric consumption is largely biomassderived food and clothing, water and energy mainly using fossil fuels, but an increasing amount of hydrocarbon synthesized materials are used in...
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