UK oil and gas industries top North Sea discharge league

Oil discharges to the North Sea from offshore oil and gas operations and oil refineries continued on an improving trend at the end of the 1980s - but the UK's contribution was bigger than that of all other countries put together, according to a report by the Paris Commission.1

Both the Commission's report and a survey by CONCAWE, the industry's European environmental organisation,2 show that the long-term improving trend in refinery discharges was sustained at the end of the 1980s.

CONCAWE's report shows that oil discharges from western European refineries were cut by more than two-thirds between 1981-90 (see table ). The 95 plants which responded to its 1990 survey represent 80% of the region's refining capacity.

The discharge reductions achieved in the early 1980s were mostly attributable to the closure of ageing refineries in the wake of the oil price shocks of the 1970s. But, as the table shows, much of the subsequent improvement was the result of investments in higher standards of effluent treatment.

The Paris Commission's report tells a similar tale, but in considerably more detail. The Commission's figures are based on official returns from countries bordering the North Sea and north-east Atlantic, and cover 63 refineries.

According to the report, total oil discharges from these plants decreased from 9,049 tonnes in 1981 to 3,174 tonnes in 1990, while the amount of oil discharged per million tonnes of oil processed declined from 31 to 9.1 tonnes.

The UK's 13 refineries perform badly on several indicators:

  • UK refineries accounted for 54% of the total oil discharge in 1990. The next largest contribution (15%) came from Germany's 14 refineries.

  • Ten refineries had only gravity separation equipment in 1990. Seven of these are in the UK.

  • In 1990, UK refineries discharged an average of 19.3 tonnes of oil per million tonnes of crude processed. The next highest figure, 15.2 tonnes, was for Portugal, while in other countries the range was 0.7-8.0 tonnes.

  • Five UK refineries discharged more than 50 tonnes of oil in 1990, compared with seven for the rest of the Paris Commission area.

  • Despite the incomplete data available, the evidence suggests strongly that UK refineries discharged much the largest average loads of BOD, COD, phenolic compounds and sulphides.

    UK refiners have always maintained that their discharges are higher than those elsewhere in Europe because its plants are located on estuaries which can assimilate larger pollution loads than the waters into which its competitors discharge.

    However, data given in the Paris Commission's report for the first time tend not to support this contention. The 11 UK refineries discharging directly to estuaries discharged an average of 153 tonnes of oil in 1990. But the nine continental refineries located on estuaries discharged less than 10 tonnes of oil on average - while another 13 coastal refineries had an average oil discharge of 24 tonnes.

    Until now, the Government has supported UK oil companies by refusing to accept a Recommendation on refineries adopted by all other Paris Commission states in 1989. The Recommendation's key requirements are that, from 1 January 1994, refinery effluents are subject to biological or equally effective treatment, the annual average oil content of effluent should not exceed 5mg/l, and no more than three grams of oil should be discharged per tonne of feedstock.

    Most UK refineries would not comply with these requirements, the report shows. In 1990, only five had biological treatment systems; eight had an annual average oil discharge of more than 5mg/l; and 11 discharged more than three grams of oil per tonne of feedstock.

    It remains to be seen whether the Government will change its position in the light of the recent report on water pollution by the Royal Commission on Environmental Pollution. This urged it to end its reliance on the capacity of the environment to assimilate wastes, and move towards controls based on the capabilities of pollution abatement technology (ENDS Report 209, pp 18-20 ).

    Meanwhile, the Paris Commission's report shows that the

    UK is also the dominant source of oil discharges from offshore oil and gas operations - a position which is not entirely due to its lead as an oil producer. The report shows that:

  • Oil discharges from offshore installations totalled 19,080 tonnes in 1990 - the lowest figure since 1983, and a reduction of one-third from the peak discharge of 29,690 tonnes in 1988. The UK's contribution was 16,375 tonnes in 1990 - 86% of the total.

  • The main source of oil discharges was the disposal of spent cuttings from drilling operations. This contributed 13,739 tonnes in 1990, or 72% of the total. Operations in the UK sector accounted for 12,312 tonnes.

    The UK's dominance reflects the continuing large-scale use of oil-based muds in North Sea drilling operations. While only 56 of the 169 wells drilled in 1990 by operators from other countries involved the use of oil-based muds, these were used in 260 of the 314 wells drilled in the UK sector.

    Discharges from this source will be reduced following the adoption of a new Paris Commission Decision in September which discourges more strongly the use of oil-based muds, and reduces the existing target standard for the maximum oil content of cuttings discharged to sea from 100 to 10 grams per kilo of dry cuttings with effect from the end of 1993 for exploration and appraisal wells.

  • The second largest source of oil discharges in 1990 was contaminated production water, contributing 3,784 tonnes. UK platforms accounted for 3,187 tonnes.

  • Seventy of the 191 offshore installations breached the target oil discharge standard of 40mg/l in 1990 - an increase from 21 out of 149 installations in 1985. Most of the breaches in 1990 occurred in the Dutch (37 installations) and UK (29) sectors. One UK oil installation which breached the standard discharged no less than 1,737 tonnes of oil in 1990.

  • Oil spills were third in the list of sources, totalling 1,397 tonnes in 1990. The UK's contribution was 876 tonnes.

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