Arriva NL operates a bus from Groningen to Emden every 3 hours. Tickets cost $11 - $17 and the journey takes 55 min. 2 other operators also service this route. Alternatively, Dutch Railways (NS) operates a train from Groningen to Emden hourly. Tickets cost $13 - $23 and the journey takes 1 h 14 min.
From Groningen bus to Leer(Ostfriesl) then train to Emden Hbf. 1 h 20 min 24€. From Groningen train to Leer(Ostfriesl) then train to Emden Hbf. 1 h 39 min 32€. From Groningen drive to Emden. 1 h 4 min 14€.