Its a pretty big subject!!! What industry are you in? Who is your audience? How much depth do you need? Is it awareness training? Sadly its rarely the case we can just wing something across. Why don't you use your environmental policy as a starter for 10 and work your way through that explaining what it means, what it covers and how it applies to your company - should cover a good range of things that could easily fill a presentation. Further down the page another post is asking fo same - worth you having a look at the responses there too?