If you have any sense of environmental concern you wont use detergents to 'emulsify' the bilge
oil. Oil thats emulsified by detergents is perhaps more deadly to marine
life than 'visible' oil.
Sure, the best way is to use an emulsifying agent such as a caustic or 'modern' detergent / bilge
cleaner / surfactant etc. etc. etc. to get the bilge surfaces clean; but, then additionally consider to use an absorbant material to further absorb / extract the oil from the emulsion BEFORE pumping it overboard
. Most 'oil-boom' materials are simply polypropylene fibers (fluff), as polypropylene is a powerful 'oleophillic' (oil absorbing) material. Simply wash / emulsify the oil in the bilge, then take one or two of the 'oil absorbers' (take it apart ... unroll it!!!!) put it in the bilge to absorb the emulsified oil. It may take several days for the absorbance to complete. Then if you cant properly dispose the absorbant, let it dry out then simply burn it.
The use of microbes for oil absorbtion is also a very good and perhaps more responsible idea.
On my boat, I have a drip pan under the engine
and to make it even easier to clean the bilge, I simply line the drip pan with a thick layer of polypropylene fluff .... the oil get absorbed directly to the pad, any water goes right through, etc. .... and since the oil never gets to the bilge ...... .