## 3 WLTC-Based Analysis of Study Results
### Ecological Parameters  
Internal combustion engines emit around 200 chemical compounds, many harmful to humans and the environment. The WLTC study measured and assessed emissions regulated by the European Union's emission regulations. The study analyses emissions of CO, HC, NOx, and CO\({}_{2}\). The main aspects of the harmful effects of these chemical compounds are as follows: CO has direct toxic effects on humans through the inhalation of air containing even low concentrations of this gas and can cause death at higher concentrations; HC causes respiratory and ocular mucosal irritation, affects the nervous system, and can lead to oncological diseases; NOx is toxic via direct inhalation, can cause oncological diseases with prolonged exposure, contributes to the formation of smog and acid rain, and depletes the tropospheric ozone layer; CO\({}_{2}\), at higher concentrations, impairs human well-being and is a major contributor to the greenhouse effect. CO and HC are products of incomplete fuel combustion and exhibit similar trends with changes in fuel composition. In the first test phase (i), the CO concentration measured before the catalytic converter (Figure 6a) showed that the average CO level decreased by approximately 6.0% and 7.5% during the WLTC cycle following the transition from E0 to E10 and E70, respectively. Based on the mass and properties of the exhaust components, it is estimated that the engine running on pure gasoline (E0) emitted around 80.9 g of CO over the test cycle (\(E_{\text{CO\_E\_WITC}}\)) before the catalytic converter (Figure 6a), corresponding to a specific emission of approximately 3.49 g/km. When the engine operated on E10 and E70 fuels, there was a slight difference in total CO emissions during the WLTC cycle, with both fuels producing around 65.6 g of CO, resulting in a specific emission of 2.83 g/km--approximately 19% lower compared to E0; similar trends have been found in other studies [41]. The change in pollutant emissions does not always correspond directly to the change in the pollutant concentration when altering the bioethanol content in the fuel mixture. This discrepancy arises because total pollutant emissions over the test cycle are determined by summing the calculated emissions for each second of the test. The result is influenced not only by the concentration of the pollutant but also by the mass of the exhaust gases and other factors. The catalytic converter further oxidised incomplete combustion products, resulting in a reduction of the CO concentration downstream (measurement step ii) by approximately 170 times (Figure 6b). The WLTC CO emission using E0 fuel was approximately 0.47 g (Figure 6b), with a benchmark emission of 0.020 g/km. Switching the fuel from E0 to E10 and E70 resulted in further reductions of approximately 25% and 28%, respectively, in the specific emissions \(E_{\text{CO\_WITC}}\) to 0.015 g/km and 0.014 g/km. Figure 5: Fuel and air consumption during the WLTC are performed using different fuels: (**a**) fuel consumption; (**b**) air consumption. The Toyota Prius II, under the test, is required to comply with the Euro 4 emissions standard, which mandates that CO emissions remain below 1.0 g/km. With E0 fuel, the CO emissions were reduced by approximately 50 times due to the efficiency of the catalytic converter. The addition of biotechnol further reduces CO emissions significantly, attributed to the lower carbon-to-hydrogen (C/H) ratio, improved combustion from the increased oxidant (O\({}_{2}\)) concentration, and advanced ignition timing. The latter increases the combustion temperature by occurring in a smaller volume, contributing to reduced brake-specific fuel consumption. However, it is observed that at the beginning of the test cycle, in low-speed mode (I), the engine running on E10 fuel produced lower carbon monoxide emissions than when running on E70 fuel. This is because the higher bioethanol concentration in E70 fuel reduced the exhaust gas and catalytic converter temperatures in this mode (Figure 3b).