And that is the distinction that I'm seeking to draw between the use to which materials are put and the materials themselves.

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His system has a design that makes it easier to get the air through it, uses cheaper materials and does not draw electricity from the grid, which adds to costs and reduces the net amount of carbon stored (since grid electricity comes with carbon emissions attached, from the fuel used to make it).

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Elephant dung is one of many materials the artist uses in his works, which draw on collage techniques and employ acrylic paint, paper collage, glitter and map pins on canvas.

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Mr Lansley says he will draw the review team's attention to the work of the Surgical Materials Testing Laboratory based in Bridgend, after Ms Griffiths suggested the English NHS might wish to use it.

BBC: Andrew Lansley