Playing game without steam

Is there a way to copy the steam version that i have onto a portable hard drive and play it off that. Does it require steam? I no longer have access to my Serial Key but could get it if it is really necessary. (It's in my dad's email) Could I just copy it over and play on a computer that doesn't have steam installed. I have final exams coming up and want to play it in the time after in my GD class.

 

Beamng is independent of steam, as in it can run without steam. Dont try running from usb though, i heard it takes forever to start.

 

its not too bad, I've done it from a portable hard drive. Copying to the native drive would be better of course though.