Not sure if he really said that one or not but it doesn't look like gold is bigger damage to the environment itself. Never thought of this comparison before but its worth thinking about it. I mean truly we keep saying that bitcoin using the huge electricity in terms of the mining operations which are needed for the existence of the same. Later on we also started to think that bitcoin is responsible for the global warming due to its mining operation and the heat that it produces!! I mean thats the worst case we have thought about the bitcoin. But truly if you just see the documentaries about the Gold mines and rigs then we will understand that is even huge cost involved and polluted operation ever.  

So I am pretty sure we need to re-think about the bitcoin and gold and which one is better for the environment.