It's not a wase of energy at all. Just like data centers, mining farms produce a lot heat which can be used to heat nearby houses and other buildings in the winter if the farm in question is large enough.
The average US household uses 10 to 12 000 kWh in electricity each year, about the same as would be required to generate four Bitcoins worth a little under $1,000. But the same average household has about $6,000 in cash on hand and savings accounts, and around $15,000 in credit card balances. Switching even a small part of a typical household's financial transactions to Bitcoins must therefore entail a massive increase in electricity use.
For some reason he seems to think people can only get or use BTC by mining (rather a stupid mistake for a professor to make).
I have seen top bank investors talking trash about Bitcoin, governments, and so on. They can't seem to understand how Bitcoin really works and what it is capable of. Ignorance at the highest level from people you would expect it the least.