Zero propellant thrusters

Is it possible to create thrusters for station keeping that require no fuel? Are there ideas similar to solar sails which can help in station- keeping and make use of a natural phenomenon? Except the EM drive.

• Air breathing Ion thruster's have been developed lately (article from 5 March 2018). They use the thin air on low earth orbit as propellant. – Christoph Apr 9 '18 at 14:02
• Then there's the photon propulsion, which unfortunately provides way too little thrust for station-keeping. – SF. Apr 9 '18 at 18:11
• +1 for "Except the EM drive." – uhoh Apr 10 '18 at 2:04