This is the fourth episode in the series Energy Explained: Behind the Headlines  Pete Buttigieg, the recently confirmed US Secretary of Transportation, informed the press that he intended to focus on high speed rail as part of his infrastructure growth thrust.  Vikram opined that while the growth per se had bipartisan support, he was not bullish on high speed rail for the US, even though aspirationally it was a good idea.  Since such a long term project would span administrations, survival may be in doubt even if commenced.  Malaysia just canceled theirs, California has been stumbling on its entry and the London to Birmingham project cost nearly doubled, putting that in doubt.  Shorter term public transport such as urban rail would be a good start.   No matter what form the infrastructure growth takes, roads, rail, bridges, they all use steel and/or concrete.  These two are the largest industrial producers of CO2.  The growth will inevitably add to the greenhouse gas burden.  Given that the Biden administration has also committed to climate mitigation measures, any infrastructure build ought to be accompanied by initiatives to decarbonize steel and cement manufacture.  This could be any combination of research, development and deployment.  In the last category could be loan guarantees and similar financial inducements.  The good news is that the steel industry and cement manufacturers are keen to become greener, and so would be receptive.