IT always seemed a question of when, rather than if, the burning of controversial chemical waste Cemfuel would resume at the Ribble Valley plant of Castle Cement.

For the new European anti-pollution rules that led to a freeze on its use at the end of June have evidently not swayed the company from its belief that this fuel is safe, environmentally and health-wise.

And now as it applies for Environment Agency permission to start burning Cemfuel again in one of its kilns - as a substitute for coal by as much as 40 per cent - it not only restates its environmental claims, but adds a crucial point.

That is that the future of the whole works, the jobs there and the vital role the plant has in the local economy rest on this kiln. This may not mean that they depend on the burning of Cemfuel in it. Nor even burning old tyres, which the firm is now considering.

Hugely important as Castle Cement's role in the Ribble Valley economy is, it remains vital that its operations comply with every official safeguard for the health and the environment no matter what the commercial considerations are - and that there is public confidence in both the regulations, in their being upheld and in the regulators.

And even though the Environment Agency's teeth were shown last month when the company was fined £45,000 for pollution offences, it has been this lack of confidence that has kept the Cemfuel controversy raging for eight years.

It remains to be seen whether it can be dispelled by Castle's claims today that its trials of burning it and tyres have shown actual environmental benefits or even if doubts can be assuaged by this new Cemfuel bid being evaluated by an independent assessor.

This makes it as vital as ever that Cemfuel controversy is nailed once and for all by scientific proof that is safe. As the endurance of this row shows, that may be difficult, but, surely, it is not impossible.