You should dispose of your old empty edding markers together with non-recyclable waste. In countries with a recycling collection service the markers can be disposed of in the appropriate container.
In Germany, we offer our major customers (e.g. administration departments, seminar centres, industrial companies) special returns boxes for collecting used markers that have run out of ink. These boxes are free and can be ordered via email. When full, the returns boxes can be returned to edding free of charge and the pens are then sent for recycling.