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The aim of this paper was to investigate the possibility of reusing frying oil, obtained during thermal treatment of food in fast-food restaurants for production of plastic greases.

In accordance with the proposed research concept, the used frying oil was to be the base oil of biodegradable plastic greases thickened with calcium 12-hydroxystearate and lithium 12-hydroxystearate. These studies included the determination of the effect of variable amounts of used oil component in the base oil on the properties of the resultant plastic greases.

It was found that the optimum amount of the component in the base oil is 10-15 per cent. Calcium and lithium greases prepared in such a way possess a quality to that of greases prepared with fresh rapeseed oil.

Higher concentrations of used frying oil in the base oil adversely affect the degree of thickening, thixotropic properties and dropping point of the grease, as well as, creating technological problems.

The investigations, beside their research goals have also a practical character – recycling waste material in place of its present method of disposal.

One of the least expensive material, and most commonly used to produce biodegradable lubricants are vegetable oils. In recent years, besides introducing biodegradable lubricating oils, increasing interest is observed in the use of plastic greases of high biodegradability. Now, it is possible to obtain such greases with additive of used frying oils. Biodegradable greases are used as lubrication of open gear, food production equipment, central lubrication system in cars and railway engineering.

In the second half of the 1980s, together with Perestroika in the Soviet Union, a process took place to end the Cold War as a confrontation between the United States of America and the Soviet Union. At the same time, this process caused the collapse of the Soviet Union and socialist system and thereafter the separation and independence of the many nationalities that constituted the Soviet socialist system in the East and South Europe. However to our regret, such nationalities could not enjoy freedom by independence, but went to brutal wars between separated nationalities. Even after many local wars and brutalities we cannot yet find the final solution through peace and justice for peoples.