Image source: Getty Images Fortescue Metals Group Limited (ASX: FMG) shares are under the spotlight as one of its main resource rivals questioned the future of green hydrogen. As some readers may know, Fortescue has a division called Fortescue Future Industries (FFI) which is planning to create a portfolio of green energy-producing locations around the world. Fortescue thinks that green hydrogen and green ammonia is the answer of how to decarbonise a number of sectors that are hard to lower emissions, including aircraft, ships and heavy machinery. Questions raised According to reporting by The Australian, Rio Tinto Limited (ASX: RIO) chief scientist Nigel Steward doesn’t think that hydrogen can be used as an “energy carrier” in the near future because of its production costs and problems with shipping. Steward said: Hydrogen is much hyped, particularly as an energy carrier. We…