Cork is greener than the Diam and screwcap, according to the first carbon footprint study into closures produced for Diam bottle-top producer Oeneo Boucharge by Cairn Environment.

The research found that natural cork, dressed with a PVC capsule, emits 2,490kg of equivalent carbon dioxide by tonne. The Diam closure, also PVC dressed, has a carbon footprint of 4,253kg, while Siam's S-Cap's screwcap has more than 10,000kg.

Dean Banister, Oeneo sales director, said: "This research is the initial phase of our efforts to reduce our carbon usage, which will include a detailed evaluation of our energy sources, packaging and transport."