COPENHAGEN (Reuters) – Danish engineering group Topsoe plans to build Europe’s biggest plant making electrolysers – machines that produce the green hydrogen considered a cornerstone of the shift to cleaner energy. Hydrogen is categorised as green when made using renewable power, and is seen as critical in helping to decarbonise hard-to-transition industries such as steelmaking and heavy transportation, though the technology is immature and costly. The Danish plant will start running in 2024 and comes with a 2 billion Danish crowns ($284 million) price tag, Topsoe’s Chief Executive Officer Roel…