But such closure also puts at stake the survival of more than 30,000 families associated with these units. A better alternative suggested by the Supreme Court was to clean up the technologies of the foundries so that emissions could be brought down to under permissible limits.

In one of its judgements related to pollution in the Taj Trapezium, the SC ordered the Central government to explore the possibility of providing gas asa fuel and to introduce suitable measures so that the foundries can clean up their act.

Indian technologists have risen to the occasion. Using new technology developed by the Jamshedpur-based National Metallurgical Laboratory, it is now possible to design eco-friendly melting furnaces, which can convert the large number of foundries and bangle-making units in the Taj Trapezium into less polluting units. The system can also be replicated elsewhere in the country where clusters of foundries operate.

Earlier, the Union ministry of Environment and Forests had appointed a high-level committee of experts to investigate the pollution problems caused by the emissions from the conglomeration of foundries in the vicinity of the Taj Mahal. Headed by Dr S Varadarajan, the committee concluded that one of the main reasons for the presence of the yellowish tint on the white marble stone of the world famous monument was be- cause of high levels of corrosive emissions of suspended particulate matter (SPM) and gaseousemissions of sulphur and nitrogenous oxides.

The SPM level monitored in Agra by the committee was found to be an alarming 1,2000-mg/Nm3; the sulphur dioxide level was found to be 350-mg/Nm3. Coke is considered the main culprit: Its ash has a high sulphur content that lets sulphur dioxide emissions into the atmosphere. Conventional copulas fired by coke let out high levels of SPM, SO2 and NOX. The problem is aggravated as the coke used in these copulas contains around 0.7 per cent sulphur. This translates into 260-300 kg of sulphur in every tonne of coke.

The harmful levels of corrosive emissions were found unacceptable by the Supreme Court in its verdict in a public interest litigation. Taking up the task, NML has fabricated a cost-effective, indigenous, eco-friendly melting furnace that will help turn the hundreds of foundries in Agra into more efficient and less polluting units.

NML has been supported in the project by the Technology Information Forecasting Assessment Council under its Home GrownTechnology programme.

NML carried out trials last year using indigenously developed burners supplied by the Calcutta-based Wessman Engineering Company. It has since also transferred the technology to Tata Korf, a Tata group company. The feasibility was demonstrated in trials carried out recently. The cost of designing and installing a new copula that uses natural gas has been put at nearly Rs 12 lakh. The existing copulas could also be redesigned and modified at a fraction of the cost of a new one. These will, however, not be as energy efficient as the new copulas.

Previous to these demonstrations, NML has conducted 50 successful trials, replacing coke used in furnaces with low-sulphur, light diesel oil and light petroleum gas in a modified demonstration scale of a one tonne per hour copula.

In both these fuel sources, the sulphur content is less than 0.2 per cent. It was also found that the rate of fuel used came down around 70 litres per tonne. Correspondingly, the sulphur emitted into the airwould be a tenth of what is let off by coke-fired copulas, maintain NML scientists.

The scientists at NML are naturally jubilant. They claim that the techno-economics of their cupola is more attractive than that of the coke-fired copula as the production cost is Rs 655 per tonne when natural gas is used, and around Rs 900-1,100 when coke is used. Small foundries can obtain the natural gas from the GAIL.