Lots of film camera had batteries in them that weren't rechargeable. After being used they would just be tossed away into landfills. You also have to consider all of the plastic used in making the film rolls and then casing the film rolls. There was energy put into making all of those items that you don't see in digital.
I am not saying one is better than the other, but you have goods and bads of each.
Have any studies been made to validate whether or not the photographic community has made less of a negative impact on the environment as a result of the migration towards digital cameras?
At first glance, the answer might seem an obvious "yes" due to the lack of any chemical processes. But would it still be yes after all the energy consumed in making the processor chips, flash memory and Li-Ion batteries and the energy consumed in using the PC as a digital darkroom was factored in? I recently saw An Inconvenient Truth and have been re-examining how all facets of my life contribute to CO2 emissions. Most photographers honor nature with the images they create. I'm just hoping those same photographers are not inadvertently destroying the very thing that inspired them to pick up a camera in the first place.