## 1 Introduction
On the other hand, HC and CO emissions increased due to varying reactivity of fuel components, also increasing NOx emissions, especially at low engine loads [4; 6; 49; 52; 54; 55; 58]. The use of biogas containing up to 73% methane yields a significant ecological effect on engine life from P. pinnata plant biomass. Their use reduces NO, CO\({}_{2}\), and smoke by 39%, 42%, and 49%, respectively, using a 0.9 kg/h biogas stream. This results in a corresponding reduction in diesel fuel consumption of 0.215 kg/h [60]. With the dual fuel system and engine compression ratio at 18, diesel fuel consumption can be reduced to a maximum of 79.46%. Increasing the compression ratio from 16 to 18 can achieve the ecological effect: 41.97% for HC and 26.22% for CO [61]. Similar reductions in diesel fuel consumption are also observed with industrial dual fuel engines in the fertilizer granulation process. The effect observed was up to 63% replacement of diesel with natural gas [62]. The biogas mixing ratio in the mixing chamber and the dimethyl ether (DME) injection time significantly influence the combustion and emissions characteristics of the biogas-DME dual fuel in a modified single-cylinder diesel engine. Increasing the biogas to DME mixing ratio reduced the maximum combustion pressure, led to a slower ignition time, and decreased the increasing combustion pressure. As the biogas mixing ratio increased, the peak and gradient of heat release rate (ROHR) decreased [63]. Increasing the oxygen concentration to 27% in the air supplied to the dual fuel results in lower fuel ignition times and methane emissions. At 40 brake thermal efficiency (BTE) engine load increased to 28% [64]. The use of diethyl ether (DEE) in dual-fuel biogas engines shows that the biogas-DEE HCCI mode shows a higher operating load range and higher brake thermal efficiency (BTE) at full load compared to biodiesel and biogas SI (spark ignition) modes [65]. In the bi-fuel mode, the biogas/b biodiesel blend engine achieved maximum pressure compared to the biogas/diesel low-load engine, but slightly lower heat output. At 60% load, biogas and biodiesel combustion showed slightly higher pressures, heat dissipation rates (ROHR), and average effective pressures (IMEP) than biogas diesel engines [66]. A cheap source of biodiesel finding is a very pressing issue in today's fuel production [67; 68; 69; 70]. Thus, the alcohols will be used in the processing of forest, food, and other biomass waste if it is suitable for use as a fuel in the transport sector. One of these products is HVO (Hydrogenated Vegetable Oil), which has huge resources [71]. Policies and regulations have a direct impact on the use and production of HVO on a global scale [72]. It is renewable and has properties similar to diesel [73]. Its use improves the environmental performance of the engine: significant reduction in CO and HC emissions and a slight positive impact on NOx, CO\({}_{2}\), and smoke/PM emissions and engine power [74]. This tendency is also noticeable when operating vehicles fuelled by HVO mixtures and under adverse environmental conditions (up to -7 \({}^{\circ}\)C) [75]. In addition, no significant difference in spray dynamics between HVO and EN590 was observed, which also promotes the use of such fuels [76]. Table 1 lays down the properties of the analyzed fuel [53; 56; 77; 78; 79; 80]. The aim of the research was to find the change in energy and environmental parameters of a compression ignition engine having used the dual fuel power system and with the engine running on different fuels: diesel-natural gas, diesel-biogas, HVO-natural gas, and HVO-biogas and when changing SOI. This study is relevant because there are few studies by other authors that use 100% biofuels in dual-fuel engines: biodiesel (HVO) and biogas (biomethane).