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  17 December 2014 Last updated at 10:15 GMT
  Will Watson was speaking after calls for the mining firm to accept the "moral responsibility" for cleaning up two major sites at Margam near Port Talbot and East Pit near Ammanford following the collapse of a fraud case.
  The cost has been estimated at around Â£150m.
  Celtic Energy transferred ownership of the mines to a firm in the Caribbean, leading the Serious Fraud Office to accuse six people including two former directors of trying to avoid paying restoration costs.
  A judge threw out the case.
  Mr Watson, speaking to Oliver Hides on Radio Wales, said the firm had accepted that for Margam the prospect of further mining to help pay for restoration costs was not an option.
target: The chief executive of Celtic Energy has said there needs to be collaboration between companies, councils and government to resolve the problem of opencast mining sites which need restoring.