In the scope of the green energy and climatic changes waste poses as a great resource as an alternative fuel or source for their production. This helps to decrease the need for fossil resources, as well as diversify energy production. This kind of waste utilization and mitigation therefore directly fits into latest legislation and green initiatives. This paper focuses on the influence of five synthesis gases with relatively high heating values on the internal parameters of the internal combustion engine intended for cogeneration. Measurements show that proportion of the hydrogen in the mixture has indirect influence on the combustion duration and also maximal pressure rise rate. Interestingly hydrogen proportion in fuel showed no direct influence on the maximal in-cylinder pressure. Higher CO to CH4 ratio reduced burn time and increased maximal combustion pressure with slightly decreased performance. Concentration of CH4 directly influenced volumetric