The mercury pollution of water because of the use of mercury cells in caustic soda manufacture is responsible for reduction in the application of these cells in spite of their many advantages over diaphragm cells.
Japan has had serious problems of mercury pollution which ultimately resulted in the issue of an ordinance for discontinuation of the use of mercury cells. The world’s known reserves of chromium are about 775 million m. tonnes, of which 1.85 million m.
tonnes are mined annually at present. Thus, at the current rate of use, the known reserves would last about 420 years. The actual world consumption of chromium is increasing at the rate of 2.6 per cent annually. If the exponential relationship in an increased rate of consumption is assumed, the reserves would last for only 95 years. If the undiscovered reserves increase the present reserves by five times, this would extend the life time of reserves only from 95 to 150 years. The lifetime of aluminium is estimated to be 100 years using a static index, 31 years with an exponential index, 55 years with a five-fold increase in reserves.
Copper, with a life time of 3 6 years at the present usage rate, would actually last only 21 years at the present rate of growth, and 45 years if reserves are multiplied by five gives the position of reserves of nonrenewable natural resources and their life time using static and exponential indices. Taking into account economic factors such as increased prices with decreased availability, it would appear at present that the quantities of platinum, gold, zinc, lead, etc., are not sufficient to meet demand. At the present rate of expansion, silver, tin and uranium may be in short supply even at higher prices by the turn of the century. By the year 2050, several more minerals may be exhausted if the current rate of consumption continues. Taking the example of lead, in 1960 global demand had risen to 4.
5 m. tonnes year, but reserves had risen to 90 million tonnes due to further discoveries. However, extrapolation as a paper exercise show that by the year 2020 there would be a demand of 25 m. tonnes/year, which if an R: P ratio of 20 were the norm require 500 m.
tonnes of reserves which are just not there. The lifetime of estimated recoverable reserves of mineral resources is shown in Figure 19.2. The consumption of these minerals, in a more efficient manner, would help in minimizing pollution and conserving materials as well as the energy spent on them. Recycling appears to be one of the best ways to meet this end. This is illustrated by the following relationship: The production curves being exponential to reserves, depletion would be faster and the effect of recycling will have less impact due to the time lag between raw material production and its arrival back to scrap cycle. It is obvious that the adoption of recycling in an exponential growth situation can only mildly assist the inexorable march of resource depletion. Obviously, a static consumption situation is required with maximum recycling to conserve resources in on long-term and not short-term basis.
Thus recycling can aid both energy and material conservation. It alone cannot assure a steady state situation but it can buy time, conserve resources and, if properly applied, minimize both energy consumption and environmental impact. The problems associated with adopting recycling may be the cost factor, obtaining of proper know-how, etc., which could be overcome by proper planning. The problems of cost could be tackled by legislature, tax relief, cash incentives, development rebate, etc.
This would encourage industries to even invest in setting up of plants for waste processing and encourage conscious industrialists to come forward with new ideas of controlling pollution. The chain reaction, so started, will go a long way in conserving energy and materials, minimizing pollution and providing a better environment to mankind to live in.