Cleaning up marine oil spills can be a challenge as there are various types of oil spilled but only a few effective recovery methods. The three main technologies for oil spill recovery for inland and offshore waters are mechanical, insitu burning (ISB), and dispersant application. Absorbent booms and pads may also be used, but they are more effective for small fuel spills.
Mechanical recovery, usually an oil skimmer, is a device that skims contained floating oil and transfers the recovered oil to a storage container or vessel. Selecting the appropriate oil skimmer depends upon the oil’s viscosity, slick thickness, adhesive characteristics and weathering properties. Sea states and the ability to access and encounter the oil are also important factors, among others. It is possible that more than one type of skimmer may be needed on a single spill.
No “one-size-fits-all” skimmer
Since there are various types of oils, from crude to refined, as well as various types of environmental conditions, there is no “one-size-fits-all” skimmer. Oil viscosity is one of the most critical parameters affecting a skimmer’s recovery performance. At opposite ends of the viscosity, spectrum are light and heavy oils. Gasoline and diesel fuel, as well as Bakken crude, are light oils. They spread and evaporate quickly. Heavy oils, such as bunker and bitumen, are more viscous and can cause more environmental harm as they linger longer and may even sink. Medium viscosity oils are, well, in the middle and are somewhat easier to recover mechanically.
Oil skimmers come in all sizes, configurations, combinations, and materials: drums, discs, ropes, brushes, belts, weirs, suction, aluminum, steel, polymer, pneumatic and hydraulic. Oleophilic polymer skimmers generally recover a higher ratio of oil relative to water and are also effective in recovering medium viscosity oils. In 1990, Elastec, an environmental equipment manufacturer in Carmi, Ill., perfected the oleophilic smooth drum skimmer which remains an industry standard today due to its high oil recovery rate and recovery efficiency (oil-to-water ratio).