The main purpose of this research was to determine the chemical composition of deposits in gas engines fuelled by coal mine methane (CMM), as well as its dependence on the place of collection. This composition was compared with that for deposits formed in biogas-powered engines. It was also found that the chemical composition of deposits varies depending on the place of their formation in the engine and on the gaseous fuel used. The dominant mineral deposits found in gas engines fuelled by CMM contained Ca, Zn, P, and S, which originate from oil additives. The Al, Cr, Cu, Ti, and Fe elements present in the tested samples are related to the wear of the engine under normal operation. The remaining trace elements can originate as impurities from the air.
