Waste: A Game of Snakes and Ladders? : Chemical Case Study
Taking on Responsibility
For most companies, managing their own waste is enough of a problem. Few would wish to take on someone else's waste history. But that is exactly what DuPont did when it purchased an ethyne plant at Maydown in Londonderry, Northern Ireland.
The site had been operated by a chemical company which provided Dupont with ethyne to produce synthetic rubber, but over a number of years alternatives were identified and the plant became obsolete. The chemical company closed the site and, due to contractual terms, DuPont acquired responsibility for it in 1980. with this it acquired a sizeable waste problem that had built up over two decades. In the 1960s, processes for producing ethyne had resulted in lime waste which had been stockpiled. In the 1970s, an alternative process had resulted in tar as a by-product. At the time there was no viable process to deal with the tar, so large pits were dug in the lime waste, where over 40,000 tonnes of tar were dumped.
A detailed environmental audit by DuPont revealed that the walls of the lime pits may break and spill tar into the nearby estuary. Although there was no legislation compelling DuPont to take any action, the company felt that it was their responsibility to safeguard against environmental damage.
DuPont identified several stages in the clean up process. First the tar would need to be removed and either used or disposed of safely. any remains of the pits would then have to be decontaminated and, finally, the ecological status of the land would have to be restored. Various schemes were attempted and abandoned before DuPont identified a US petroleum company with a leading edge solution to break down the tar. In 1990 the company began treating and pumping the tar out of the pits and installed burners to enable DuPont to then use the tar as a waste fuel. Those parts of the tar which could not be used as fuel are being processed at a refinery and recovered for the tar industry. The lime-rich land is retained as a stockpile of lime used to neutralise acid in waste treatments.
Once the threat of pollution was eliminated, DuPont worked to restore the area to its natural state, levelling all the land and planting trees, shrubs and grasses. This is an ongoing project, but, with wild orchids already found growing in the area, it is fair to say that DuPont has been successful in rejuvenating this site.
Gerry Patton at DuPont, currently responsible for the site, says: 'When we took over the area it is not an exaggeration to say that it looked like a lunar landscape - scarred with pits and craters - so the transformation over the last few years is substantial.
But, of course, it is a problem that would not be allowed to happen in today's environmental climate. At the time, however, the tar was not seen as having any feasible use and dumping was a convenient option. Technological developments mean that the tar can now be used as a resource, but, even so, it would have been more cost effective and far less damaging to the environment to have dealt with the tar as it was produced than for DuPont to remedy the tar pits many years later. '
