Pyrogallol should be handled carefully, as should all developing agents, but it isn't obvious that it is harmful to the environment or any more so than coffee. It comes from trees, after all, and oxidizes very rapidly in an alkaline solution in contact with air, which is one of the reasons it fell out of favor for many years. As long as there are natural chemical pathways to break it down in the concentrations and quantities that we use, it's not necessarily an environmental hazard.

Coffee isn't likely to be a chemically consistent product. The large coffee manufacturers buy coffee beans on the international market based on price, so coffee beans grown in different soils and different climates exist in different proportions in different batches of coffee. If one starts purifying it to extract the caffeic acid in known quantities, then it seems not too different from using pyro.