Lightering is not possible in all oil spill scenarios. It depends on many factors including the type of oil that is spilled. As time passes, the oil can become more viscous, or thicker, and therefore more difficult to pump. This can, in turn, make lightering difficult, if not impossible. While there are benefits to removing oil in this way, there can also be accidents and spills that result from lightering.
Lightering is also used to transfer cargo between vessels of different sizes like a barge and a bulker or oil tanker to reduce the vessel's draft in order to enter port facilities.