Earth Day

4. Noting or pertaining to a class of chemical compounds.
5. To keep alive or in existence.
8. A mixture of various decaying organic substances, as dead leaves or manure, used for fertilizing soil.
9. Able to be maintained or kept going, as an action or process.
13. The branch of biology dealing with the relations and interactions between organisms and their environment, including other organisms.
14. A system formed by the interaction of a community of organisms with their environment.
15. Able to be renewed.
18. No longer in existence.
19. Objects strewn or scattered about.
20. To process (used goods or waste material) so as to produce something that is often better than the original.

1. The natural environment of an organism.
2. Of or pertaining to the sun.
3. To make foul or unclean, especially with harmful chemical or waste products.
6. An act or instance of emitting.
7. To prevent injury, decay, waste, or loss of.
10. The gaseous envelope surrounding the earth.
11. The aggregate of surrounding things, conditions, or influences.
12. It is found in the atmosphere.
16. A low area of land that is built up from deposits of solid refuse in layers covered by soil.
17. To use again in the original form or with minimal alteration.