# Comparative Analysis of Partially Renewable Composite Fuels Based on Peat, Lignite and Plant Oil
## 3 Results and Discussion
### Composite Fuel Gasification Products
The presence of the gas production maximum for certain RO fractions in the fuel composition clearly shows that the interaction of its components during the oxidation is maximal. Figure 5: Chemical composition of producer gas for different fossil fuel—renewable component ratios in the composite fuel. The gas trends are shown in subfigures: CO (**a**), CO\({}_{2}\) (**b**), CH\({}_{4}\) (**c**), SO\({}_{2}\) (**d**), NO (**e**). The optimal fuel compositions are 35 wt% peat and 65 wt% rapeseed oil; 60 wt% lignite and 40 wt% rapeseed oil. The gasification rate of composite fuels with different chemical compositions can be easily estimated from the changes in the total weights of produced gases versus the component ratio. Figure 6a shows the change in the producer gas weight over time in the thermochemical conversion of the P + RO composition. One can see that pure peat (the blue curve) produces the highest amount of gas. It produces more than 6 g of gas per 1 cm\({}^{2}\) of the heated fuel surface. Adding rapeseed oil slows down gasification. The conversion of the composition with 30 wt% RO is twice as slow. However, a further increase in the oil fraction slightly enhances conversion. The maximum gas production occurs when the oil fraction is about 65 wt%. This means that the local maxima obtained earlier (Figure 5) for the production of carbon monoxide and methane are coupled with an overall increase in the gasification rate by up to 80% relative to the conversion of pure peat. A further increase in the RO fraction significantly reduces gas production. The compositions contain 75 wt% rapeseed oil and produce a 6-7 times smaller number of gases, mostly due to the evaporation of the volatile component of RO. It is clear in Figure 6b that the conversion of the lignite-based compositions features a much higher overall production rate. Pure lignite can produce up to 15 g of gases per unit area (after 5 min of heating), which is 3 times higher than in the gasification of peat-based fuels. Adding RO to lignite slightly increases the gas production rate. Moreover, the compositions with 35-45 wt% RO allow a quasi-linear increase in the weight of produced gases over time (after 5 min of heating). Therefore, the maximum production of carbon oxides and methane is up to 25 g per unit area of the irradiated fuel. The overall gas production is maximum when the fraction of RO is about 40 wt%, and it decreases with a further increase in the fraction of RO. Thus, the optimal lignite-to-rapeseed oil ratio is 3:2. The green-colored area in Figure 6 shows the range of the RO concentration that allows quite effective gasification. The yellow-colored area shows the RO concentration range in which only the evaporation of volatiles from the fuel components is possible. Figure 6: Producer gas weight per square centimeter of the irradiated fuel area versus time. The fuel compositions are P + RO (**a**) and L + RO (**b**). The weight fraction of rapeseed oil is shown on the right. The light flow intensity is 880 W/cm\({}^{2}\).