The B30 fuel blend was introduced in partnership with Motherwell-based Argent Energy, which manufactures biofuel from waste products.

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Chris Argent, from the Fire Brigades Union (FBU), said he was not surprised by the rise but it was "still cheap".

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Stephen Tillman, one of the directors at Miller Argent, will give evidence to the planning inspector over the next few days.

BBC: NEWS | UK | Wales | South East Wales | Opencast goes before inspector

The inquiry followed the planning application made by Miller Argent for the reclamation of land which also includes extracting coal by opencast methods.

BBC: NEWS | UK | Wales | South East Wales | Opencast goes before inspector

The French word for money is argent, or silver.

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Argent Energy and Stagecoach have worked together on a number of projects, including the launch of bio-buses in Kilmarnock in 2007 - a fleet of nine buses which operate using 100% biofuel.

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The Mont Alto Orchestra Accompanies L'Argent (January 22 - 23), a screening of Marcel L'Herbier's epic L'Argent accompanied by the New York premiere of the score by Colorado's renowned Mont Alto Orchestra, repeating its triumph at the Telluride Film Festival.

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"With the price of fuel it's too tempting for people to say we're only producing a small amount of fuel that stays below the criteria for being a proper registered producer with all the costs and all the bureaucracy and all the burdens that brings with it, " says Jim Walker, managing director of Argent Energy.

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