earth day

2. reuse in such a way as to create a product of higher quality
5. the production and discharge of something like gas or radiation
6. a colorless toxic gas with a pungent odor
7. layer of gasses around the planet.
12. a place to dispose of refuse and other waste material by burying it and covering it over with soil
13. suns rays as a source of energy
14. the surroundings or conditions in which a person, animal, or plant operates.
16. community of living organisms in a particular area.
19. produce without involving the use of chemicals or other artificial agents

1. maintain something in the same state it is now
3. decayed organic material used as a plant fertilizer.
4. trash that is left lying in an open area
5. study of relationship between organism and environment.
8. natural home or environment of an animal, plant, or organism
9. animal that has died out
10. contaminate water, air, or a place with harmful or poisonous substances.
11. protect an environmentally or culturally important places from harm.
15. source of energy not depleted by use (water, wind, or solar power)
17. able to be maintained at a certain rate or level
18. convert into reusable material