Via themediamogul is SustainableFilmmaking.org 's Code of Best Practices for Sustainable Filmmaking.
It's not as complicated as it seems to start on some items. They provide "three sets of tools that help filmmakers put the code’s principles into action:
1) Checklists provide actions needed to create a sustainability plan.
2) Carbon trackers allow individuals to track production activities that use energy and produce carbon emission and are meant to be used in conjunction with Internet carbon calculators.
3) Web resources include environmental and sustainability-related URLs, carbon calculator sites, and suggested carbon offsetters, including Gold Standard ones that are recommended by WWF–UK."