Recyclers are a specialised ship designed to collect debris and convert it into credits. Each recycler is capable of converting debris into 10 credits each half hour past the hour at the recycler's current location.
Be aware that the debris collection occurs at the exact tick of hh:30:00. Arrival at hh:30:01 will NOT get you a collection until the next hour. Also, because it takes a couple of seconds for your arrival to register you could miss the collection with arrival a few seconds prior to the tick.
Recyclers are very weak combat units and can be countered with any unit except for scout ships. Given the importance of debris collection, and the advantage provided, recyclers are often protected by other ships.