## 3 Results and Discussion
### Thermal Behaviour, Kinetic Analysis, and Synergistic Effects  
The results from thermogravimetric and derivative thermogravimetric analysis are presented in Table 1 and Figure 3. The plastic waste sample revealed the lowest maximum temperature (T\({}_{\text{max}}\): 467 \({}^{\circ}\)C), that is, the temperature at which the mass loss rate becomes maximum. Also, plastic waste exhibited the highest maximum rate of weight loss (R\({}_{\text{max}}\): \(\sim\)9%/min) as well as the highest total mass loss of all samples and blends (about 96%). The high mass loss rate and the highest total mass loss are respectively in agreement with the volatile content and ash content of proximate analysis (see the results of the proximate analysis and Figure S2, Supplementary Material). Fuels with a high maximum rate of weight loss ignite easier, and fuels with low T\({}_{\text{max}}\) reveal low NO\({}_{\text{x}}\) emissions as they burn in lower combustion temperatures [36]. Figure 2: Proximate results of PW and its blends with LIGA presented in a Tanner diagram. More details are presented in Supplementary material. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample ID** & \(\mathbf{T_{i}}\) & \(\mathbf{T_{b}}\) & \(\mathbf{T_{max}}\) & \(\mathbf{R_{max}}\) & \(\mathbf{t_{b}}\) & **Total Mass Loss** \\  & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\%/min) & (min) & **(\%)** \\ \hline PW & 273 & 815 & 467 & 8.86 & 52.38 & 95.91 \\ PW70 LIG30 & 262 & 871 & 482 & 6.02 & 59.02 & 86.76 \\ PW50 LIG50 & 264 & 911 & 443 & 3.77 & 62.83 & 82.95 \\ PW30 LIG70 & 221 & 951 & 486 & 2.27 & 70.77 & 74.44 \\ LIGA \({}^{1}\) & 237 & 927 & 888 & 1.64 & 66.77 & 63.46 \\ \hline \hline \end{tabular} \({}^{\dagger}\)LIGA results are from previous work [23].  
\end{table} 
Table 1: Combustion characteristics of the analyzed sample (PW) and their blends with lignite in different proportions, as determined by TG/DTG analysis. Figure 3: Thermogravimetric analysis: TG/DTG graphs of all raw PW samples and their blends with lignite in different proportions under an air atmosphere with a flow rate of 3.5 L/min and heating rate of 10 \({}^{\circ}\)C/min. (**a**) TG graphs, (**b**) DTG graphs. The above is also evident in the data presented in Table 1; however, for the T\({}_{\rm max}\), there is no linear trend, e.g., the PW50-LIG50 sample exhibits the lowest T\({}_{\rm max}\) value. This could be partially attributed to the heterogeneity of the plastic waste. However, it could also be considered to be an indication of synergistic effects in the blended fuels. For this reason, the DTG curves of the blend samples were calculated theoretically by the DTG curves of the single fuels (assuming that no interaction/synergy takes place) and compared to the experimental DTG curves of the blended fuels (Figure 4). As can be seen in Figure 4, the comparison of the experimental and theoretical DTG curves of the blended fuels points out that there is no full matching, and some small deviations can be observed. The main peak at around 450 \({}^{\circ}\)C, in the experimental curves, is slightly shifted to higher temperatures, and the experimental mass loss rate (the height of the peak) is lower than the theoretical one for all three blends. However, the main peak of lignite (around 900 \({}^{\circ}\)C) is shifted to lower temperatures in the experimental curves. It seems that lignite \"captures\" some of the volatile matter of plastic waste or reacts with the char that is formed and causes the alterations of the peak of plastic waste at around 450 \({}^{\circ}\)C, but this char-lignite residue combusts at lower temperatures. Though these deviations are not substantial enough, they could be considered as an indication of the possibility of the existence of synergistic effects.