For decades, solar and wind arrays offered a visible indication that the transition toward a green economy was progressing.

But if we are to reduce — and, eventually, eliminate — carbon dioxide emissions, we will have to find a “clean” way not only to produce electricity, but also to power hard-to-abate heavy industries, such as steel, cement and fertilizer production. Solar and wind energy alone cannot do this job, but hydrogen can.

Most hydrogen produced today is sourced from fossil fuels. But there is a better way: Solar and wind energy can be used to power an electrolyzer that splits hydrogen from water molecules, producing zero-emission “green hydrogen.” The only waste product in this process is oxygen, which can safely be vented to the atmosphere. When the hydrogen is used — for example, in steel production — water is generated again, closing the cycle.