Idea # 3: If you have to write an argumentative research paper on engineering; then, it will be a good idea for you to choose the controversial topic for the paper. Green engineering is a debatable issue; therefore, you can utilize it as your controversial subject.
Idea # 2: If you are writing a paper on environmental engineering; then, you should go for a topic i.e. interesting for the readers. Alternative Energy Resources would be a good topic for you to write a research paper on environmental engineering.
Probably some kind of research paper on engineering