Green Chemistry is defined through the understanding of what is toxic too people, animals and the environment; including- Flammable, Explosive, and Carcinogenic,  from acquiring of the raw materials, manufacturing, use, and then recycling at the end of the products life cycle. Since we live on a planet with finite resources with little hope of finding resources on other planets or elsewhere then renewable sources of wind, solar, and plants rank high on the green list.  

Industry has come to realize that going Green is less expensive and profitable for example; removing the C.F.C.'s   cloro- flouro- carbons used as propellants and air conditioning as helped the environment greatly. In the paper industry chlorine bleaching tore up the fish and created toxic compounds in the water supply but now oxygen and polyoxometalate salts make the white paper process green and cfc's were replaced with more benign Freon's and carbon dioxide's.

Petroleum has proven tobe long chain polyhydrocarbons capable of being converted simply into many uses: food, fuel, engine oils, paints, dyes, plastics, and nutrition chemicals.  Some Engineers tend tobe trained to design on the flamboyant side with little regard for conservation until they discover that - "using less energy costs less money", thus Green also means having more green in your pocket.

Here are some helpful internet links for more examples of Green Chemistries:

http://www.usda.gov/       www.epa.gov/greenchemistry   www.acs.org/greenchemistryinstitute