Global Warming question?

So, tonight I was making guacamole and cursing that my avocados weren't ripe enough and should have set them next to the bananas. Don't decaying things give of gases? If so, then why are we encouraged to make compost heaps to keep trash out of landfills, but yet aren't we making more gases that will eat the ozone? Should we ban gas emmitng foods all together? Should we all be creamated instead of buried? I will lie awake all night thinking about my gy bananas.... sigh...