Table 7: New Sources of Renewable Energy
Despite the small potential contributions of new renewable sources to the total energy demand in the next 20 years, as indicated in Table 6, longer term projections may be more appropriate to show the impact of the full assimilation and use of renewable resources. The projections over the next 100 years given above suggest the substantial contribution that renewable can potentially achieve.
Medium Possibilities for Renewable Energy (Mtoe)
High Possibilities for Renewable Energy (Mtoe)
SCRAP STEEL, RECYCLING, AND ENVIRONMENTAL FACTORS
Recycled steel from scrap accounted for 45 per cent (335.6 million tonnes) of total steel production in 1995. In the United Kingdom 9 million tonnes of ferrous scrap were recycled in 1995, representing an 80 to 90 per cent recovery rate of redundant material. All three steel-making methods consume large quantities of scrap steel; the electric arc furnace generally uses 100 per cent scrap in its charge, although in recent years pure iron derived from ore may partly be used, depending on the quality of steel to be made and the price of raw materials. The open-hearth furnace commonly uses 50 per cent scrap, while the basic oxygen converter normally uses 10 to 15 per cent scrap, but, because of its dominant position in steel making, this process consumes some 50 million tonnes of scrap a year. Using scrap not only prevents the build-up of waste but also reduces the amount of energy required by a factor of 2.5 per tonne of scrap melted compared with making iron from ore. However, certain elements such as copper and tin are introduced with the scrap, making the steel unsuitable for such applications as sheet steel for car bodies and household goods unless it is “diluted” by the addition of iron made from ore.
Not only scrap is recycled: dust and mill scale that arise during the production and processing of steel are also reused. Twenty years ago, many thousands of tonnes of iron oxide dust were emitted from each steel plant, settling as a fine red powder across the neighbourhood. Today, annual emissions are measured in tonnes rather than kilotonnes. Dust emissions from UK steelworks fell by 57 per cent between 1980 and 1990 and accounted for less than 0.5 per cent of total UK particle emissions. Dust falling in the neighbourhood of Kawasaki Steel in Japan has been reduced from 140 tonnes per sq km in 1968 to 10 tonnes per sq km in 1995.
Not only dust levels, but also gaseous emissions of carbon dioxide, sulphur dioxide, and oxides of nitrogen from steelworks have been substantially reduced compared with the levels of 30 years ago. In the United Kingdom steelworks reduced carbon dioxide emissions (a contributor to global warming) by 37 per cent between 1980 and 1990, when they accounted for 3 per cent of the United Kingdom’s total carbon dioxide output. Sulphur dioxide emissions, a major source of acid rain, were reduced by UK steelworks by 60 per cent between 1980 and 1990, and now represent less than 3 per cent of the United Kingdom’s total sulphur dioxide emissions. In Japan emissions of sulphur dioxide at the Keihin Works have been reduced by a factor of 24 in the past 30 years. Similar reductions are now being achieved at most steelworks in industrialized countries, as well as substantial reductions in the former Soviet Union and Eastern and Central Europe.
The reduction in carbon dioxide emission is a result of reduced energy consumption, which has halved since 1950 in most plants operating in industrialized countries. The output of carbon dioxide, however, remains one of the industry’s biggest environmental problems to overcome, since steel is essentially a fossil fuel-based industry. Melting scrap instead of making steel from the ore reduces the amount of energy required per tonne of steel by a factor of 2.5, but electric arc furnaces still indirectly contribute to carbon dioxide emissions since most of the electricity they use is generated in coal- or oil-fired power stations, even the best of these operating at only 43-per-cent efficiency, and most at 35-per-cent efficiency or less. Most European steel plants have announced plans to further reduce energy consumption, with the aim of stabilizing the carbon dioxide output in the year 2000 to the levels of 1990. In France, for example, this will require a reduction of 2.5 million tonnes per year in emissions of carbon dioxide, a 10 per cent lowering of the 1996 level.
