Environment Report 2015

Waste Composition Last year, drill cuttings returned to shore were mainly made up of hazardous solids, hazardous oils and other hazardous liquids, such as oily water. Solids and liquids are classified as hazardous if they contain small amounts of oil. Once ashore, drill cuttings undergo thermal treatment that involves separating the solid rock fragments from the oil and liquids. The majority of cuttings were processed in the UK with just six per cent exported to the Netherlands for processing. Sludges, liquids and tank washings make up the majority of wastes from operational and decommissioning activities, with over 71,000 tonnes returned to shore last year. Liquid wastes are generally not separated from one another offshore due to physical space restrictions, giving rise to such a sizeable category. These wastes are then processed to separate hydrocarbons and heavy metals from solids and other liquids. The liquids are then treated for safe discharge to the sewer system, while the remaining materials can then be used in renewable energy facilities such as anaerobic digesters 38 . Oil is recovered and usually reused as a fuel source and the cleaned solids are disposed of in a landfill.

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The offshore industry generated almost 1,900 tonnes of scrap metal from decommissioning in 2014, which was all reused or recycled. Almost 90 per cent of the total decommissioning waste last year was reused or recycled.

Figure 18: Operational and Decommissioning Waste Generated Offshore by Category in 2014

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0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 Waste (Tonnes)

Total Disposed Operational

Total Disposed Decommissioning

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Source: EEMS June 2015

*'Other' category includes wastes such as asbestos, clinical waste, construction materials, explosives and radioactive materials

38 Anaerobic digestion is the breakdown of biodegradable material by micro-organisms in the absence of oxygen.

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