|Eco-restructuring: Implications for sustainable development (UNU, 1998, 417 pages)|
|Part I: Restructuring resource use|
|4. Materials futures: Pollution prevention, recycling, and improved functionality|
1. Each tonne of fossil fuel burned results in the ultimate release of roughly 3 tonnes of CO2 to the atmosphere, not to mention significant quantities of sulphur oxides (SOx) and oxides of nitrogen (NOx) - the main causes of environmental acidification. Atmospheric carbon dioxide concentration has increased by about 20 per cent since the nineteenth century.
2. Specifically, the first law of thermodynamics, i.e. the law of conservation of mass.
3. The quantities of ore removed from the earth are normally much larger, but physical separation techniques leave much of the excess material at the mine, where it is piled up into small mountains, but not put back into the ground. For instance, copper ores mined in the western United States contain less than 0.4 per cent copper, whereas concentrates delivered to refineries average 20 per cent copper. Thus, for every tonne of concentrate, at least 50 tonnes of crude ore were dug up and processed (by flotation ponds) at the mine. For I tonne of refined copper 250 tonnes of ore are processed. In some cases the quantities of ore processed are much larger. For example, roughly 140,000 tonnes of ore must be processed to yield 1 tonne of platinum group metals.
4. Applications of high-strength low-alloy (HSLA) steels are still continuing to increase how ever, especially in the auto industry. Major process innovations, notably the Basic Oxygen Process (BOF) and continuous casters, also appeared after World War II.
5. A 16 megabyte chip was announced in early 1987 by NTI (Nippon Telephone and Telegraph Co.). As of 1997 we are in the gigabyte range.
6. These are materials that lose all electrical resistivity at a temperature below some "critical", level so long as the magnetic field strength (including the field induced by the superconductive current itself) is below a critical level.
7. Data recording requires "soft" magnetic materials, i.e. materials that can easily be magnetized and demagnetized at high frequency without large "eddy current" losses. The latter requirement cannot be met by metals, but oxides fill the bill because of very high electrical resistivity.
8. Magnetic energy is measured in mega-gauss oersteds (MGOe).