Spent earth oil, also known as spent filter oil or spent earth, refers to the used oil that has been processed and is no longer effective for its original purpose, typically in industrial operations like oil refining or as a lubricant. It is the waste product from certain industrial processes, particularly those that involve filtration or de-oiling.

For Examole:

In the oil refining process, the oil is often filtered through a material like clay or activated earth (known as fuller's earth) to remove impurities and color. After this process, the oil mixed with the used filtering earth becomes known as spent earth oil.

In lubrication or hydraulic systems, spent earth oil can also be a result of the oil being used for a period of time and losing its ability to properly lubricate or clean the system.

Spent earth oil is considered waste and needs to be disposed of or treated properly to prevent environmental harm. Recycling methods include reprocessing the oil to remove contaminants and reusing it for energy generation or other industrial applications.

Spent earth oil, despite being waste oil, has several potential applications and uses. The methods of using it depend on its composition and the degree of contamination. Here are some common applications: