It’s all around us and has pride of place in the periodic table. Hydrogen is the number one element. For decades it’s been hailed as a potentially cleaner alternative to the fossil fuels which power heavy industry, our homes and transport systems. But hydrogen from renewable sources has never quite realised its potential. It's expensive to produce. However, as the UK now has targets to cut carbon emissions, green hydrogen may have a major part to play in the clean-up. Evan Davis and guests discuss the business of hydrogen.

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