The Trier Semester Ticket is only valid for people studying in Trier, even the Environmental Campus Birkenfeld is an administrative part of Trier university of applied sciences.
There is a separate semester ticket for the Birkenfeld location. The semester ticket of the Environmental Campus Birkenfeld is the student card. This includes the public transport on the RNN network and the Deutsche Bahn between Neubrücke (Nahe) and Saarbrücken.