Building a hydrogen-based energy system in the U.S., which some analysts call key to fighting climate change, would be based largely on fossil fuels under the bipartisan infrastructure bill heading for a Senate vote. The legislation provides for $8 billion in spending to establish at least four “regional clean hydrogen hubs” producing and using the fuel for manufacturing, heating and transportation. At least two would be in U.S. regions “with the greatest natural gas resources,” according to the bill. One hub would demonstrate production from fossil fuels, one would use renewable power, and one would use nuclear power. Coal also is listed a potential source.