Waste edible oil is oil-based substance consisting of animal
and/or vegetable matter that has been used in cooking or
preparation of foods and is not longer suitable for human
consumption. Previously, WEO was used as an ingredient in
animal feed. However, EU has banned the use of waste cooking oil
as animal feed due to the concern on animal health and the
subsequent food chain [42]. However, due to the large amount of
WEO generated annually, the disposal of WEO has somehow
become a problematic issue in most countries. WEO cannot be
discharged into drains or sewers because this will lead to
blockages and odor or vermin problems and may also pollute
watercourses leading to problems for wildlife. It is also prohibited
and will cause problems if it is dumped in municipal solid
waste landfill and municipal sewage treatment plant