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From toaster ovens that work as air fryers to hair dryers that can also curl your hair, single tools that do multiple jobs have an undeniable appeal. 

In the climate world, hydrogen is perhaps the ultimate multi-tool. It can be used in fuel cells or combustion engines and is sometimes called the Swiss Army knife for cleaning up emissions. I’ve written about efforts to use hydrogen in steelmaking, cars, and aviation, just to name a few. And a new story for our latest print issue explores the potential of hydrogen trains.