They were mining coal and using it for both heating and metal working.
They also deforested large sections of Europe for fuel (especially to make charcoal for smelting iron), building materials and to clear land for crops. They didn't really practice much in the way of sustainable forests, unless they ran into local shortages of fuel wood.
They also mined by tearing apart mountains, and threw noticeable amounts of lead into the air doing it.
> Roman-era mining activities increased atmospheric lead concentrations by at least a factor of 10, polluting air over Europe more heavily and for longer than previously thought, according to a new analysis of ice cores taken from glaciers on France's Mont Blanc.
A lot less than modern technology manages, but a lot more than nothing. And that with a much smaller population.
53 million amphoras... That is ceramic containers chugged to a pile... Not exactly sustainable or efficient choice either. Well there is lot of clay, but still not exactly sustainable approach...
That's the point. They had sustainable and clean technology. It was a sweet spot.