Planet Friendly Advertising

While driving on the freeway in Los Angeles it dawned on me that there are a huge number of very, very large signs and banners hanging off the sides of our office buildings. I also thought about the enormous number of signs used throughout the world of advertising at conferences, trade shows, exhibits, sporting events, etc. and wondered how all of that possibly toxic material gets disposed of. I also pondered why more imaging and printing companies don't offer biodegradable signs and banner services like PROLABdigial Imaging. Please let me know your thoughts.