# Medium-Energy Synthesis Gases from Waste as an Energy Source for an Internal Combustion Engine
)1 Faculty of Mechanical Engineering, Slovak University of Technology in Bratislava, Namestie Slobody 17, 812 31 Bratislava, Slovakia; [EMAIL_ADDRESS] (M.P. ); [EMAIL_ADDRESS] (I.M. )1 Faculty of Mechanical Engineering, Slovak University of Technology in Bratislava, Namestie Slobody 17, 812 31 Bratislava, Slovakia; [EMAIL_ADDRESS] (M.P. )1 Faculty of Mechanical Engineering, Slovak University of Technology in Bratislava, Namestie Slmethane production gradually increases while CO\({}_{2}\) production decreases. The last (fourth) phase begins at the point when the production of landfill gas, as well as its composition, is constant. This phase lasts from 20 to 50 years, depending on the composition of the landfill. The parameter that most influences the duration of decomposition is, in particular, the proportion of organic components in the waste. The landfill gas in this phase consists of 45-60% methane, 40-60% CO\({}_{2}\), and 2-9% other gases [3; 4; 5; 6]. For this reason, the effective gasification of municipal waste poses an interesting alternative to conventional fossil fuels such as diesel, gasoline or natural gas for production of heat and electricity in combined heat and power cycles [7; 8; 9]. Gasifying the MSW or biomass by means of gasification or pyrolysis, the MSW can be directly converted to gas consisting mostly of methane, ethane, hydrogen, carbon monoxide, carbon dioxide, and nitrogen [10; 11; 12; 13; 14]. The composition of the gas is strongly dependent on the feedstock and type of the process or reactor used. The syngas from the process can be converted to higher hydrocarbons which can substitute the oil-based conventional fuels [7; 15]. The biodiesel is commonly made through the transesterification of biologically degradable waste. The advantage of such biodiesel fuels is the high cetane number, good lubricity, non-toxicity, and low content of cetane [16; 17; 18; 19; 20]. Vegetable oils, animal fats, and all unsaturated lipids can be used for the production of biodiesel fuel [21]. Apart from transesterification, Fischer-Tropsch (FT) synthesis historically relied on natural gas and coal to produce fuels. Today, syngas can be used as an alternative to produce a range of various synthetic fuels such as FT diesel or gasoline [7; 22]. It is also possible to burn syngas in an internal combustion engine (ICE) without prior preprocessing thanks to the relatively high content of combustible compounds [15]. In current research, only representations of syngas composition premixed in pressure bottles were analysed and not actual syngas from the reactor. As was shown by [7], the incineration energy output tends to be higher than that of a gasifier-CHP (Combined Heat and Power) system. This mainly arises from the fact that ICE requires extensive pre-treatment and cleaning of the syngas from impurities such as tars, particulate matter, alkali metals, and sulphur compounds, which is a rather energy-demanding process [23]. For internal combustion engines, the limits on particulate matter (PM) and tars are of the highest priority. Particulate matter tends to block various system nozzles, mainly those of the injectors. For this reason, the maximum concentration of PM cannot exceed the limit of 50 mg/N m\({}^{3}\), and the maximum size is limited to 10 \(\upmu\)m [24]. The limits on tars cannot exceed 100 mg/N m\({}^{3}\)[25; 26]. Tars are created mainly during the condensation phase and consists of three distinct stages. The primary tars are created during the pyrolysis phase at temperatures below 500 \({}^{\circ}\)C. The composition of these tars mainly depends on the type of feedstock or biomass used [25; 27]. These begin to rearrange with sufficient oxygen supply at temperatures above 500 \({}^{\circ}\)C to form secondary tars. As the temperature in the reactor exceeds 800 \({}^{\circ}\)C, tertiary tars are formed, for which a sufficient chemical kinetics model has not yet been described. The performance of the ICE, for the given fuel mixture, depends mainly on the effective efficiency and volumetric efficiency.