Dispersants alter the balance between natural dispersion and emulsification, pushing the balance strongly towards dispersion and away from emulsification. The active ingredients in dispersants – the surfactants or surface-active agents alter the properties of the oil/water interface so that the same amount of wave energy produces a much higher proportion of very small oil droplets and emulsification is suppressed. By applying dispersant onto the spilled oil, it is possible to inhibit emulsion formation while promoting oil dispersion.


Dispersants promote the formation of numerous tiny oil droplets, and retard the re-coalescence of droplets into slicks, because they contain surfactants (surface-active agents) that reduce interfacial tension between oil and water. Surfactant molecules possess hydrophilic (water-seeking) head groups that associate with water molecules, and oleophilic (oil-seeking) tails that associate with oil. Oil droplets are thus surrounded by surfactant molecules and stabilized. This helps promote rapid dilution by water movements.

Dispersing the oil has several advantages:

  • Removing oil from the surface of the sea benefits creatures, such as seabirds and marine mammals, and habitats at risk from contamination of floating oil.
  • The formation of myriads of tiny oil droplets improve the opportunity for biodegradation of the oil by increasing oil surface area and so increasing exposure to naturally-occurring bacteria and oxygen.
  • Oil dispersed in the water column no longer drifts with the wind, being only under the influence of currents and tides. Dispersion can be a good technique to protect shorelines or sensitive resources located downwind of an oil spill.
  • Aircraft can apply dispersants, so large areas can be rapidly treated compared to alternative response methods.