Waste oils and fats represent any lipid-based substance that has become degraded, contaminated or otherwise unfit for its original human consumption or industrial use. These organic materials primarily originate from residential kitchens, restaurants and food manufacturing facilities after repeated exposure to high temperatures. Common household and commercial examples include used cooking oils - UCO (such as sunflower, canola and olive oils), animal fats (such as lard, tallow and chicken fat) and food residues such as bacon grease and meat trimmings. When improperly disposed of, these materials cool, solidify and bind with other household waste, creating severe municipal hazards.

To prevent environmental pollution and infrastructure damage, waste lipids are increasingly captured and diverted into sustainable recycling frameworks. Once filtered and chemically processed to remove moisture and insoluble impurities, they serve as excellent, low-cost raw materials for a variety of green industries. The most prominent application is the conversion of used cooking oil - UCO - and yellow grease into biodiesel or hydro-treated vegetable oil - HVO, which significantly reduces the carbon footprint of transport logistics.