## 4 Waste Conversion for Fuel Gas Production
### Specialized Additives and Catalysts to Increase the Efficiency of Pyrosis and Gasification of Waste  
The studies [44; 46; 50; 52; 63] have shown that alkaline catalysts play an important role in the pyrolysis and gasification of fuels. Microwave pyrolysis of textile dyeing sludge (DS) was analyzed by [PERSON] et al. [56]. The DS was obtained from a wastewater treatment plant for dying and printing industries (Jiangsu province, southeastern part of China). [PERSON] et al. studied the effect of additives (CaO, Ca-bentonite, Kaolin, and Fe) and oven temperature on the yield of pyrolysis products and their properties. It was found that the yield of non-condensable gases increased from 3.2 wt% to 14 wt% as the temperature varied from 450 to 750 \({}^{\circ}\)C. However, the condensate and oil yields increased with temperature changes from 450 to 650 \({}^{\circ}\)C and reached their maximum values (12.9 wt% and 0.8 wt%, respectively) at 650 \({}^{\circ}\)C. A further increase in temperature to 750 \({}^{\circ}\)C was accompanied by a decrease in the proportion of liquid pyrolysis products. When the temperature was raised to 750 \({}^{\circ}\)C, the oil underwent reforming and cracking inside the reaction zone, which reduced the pyrolysis gas yield. Studies [105; 106] also confirm that the range of 450-650 \({}^{\circ}\)C is most favorable for pyrolysis oil production, depending on the properties of raw materials, type of reactor, and operating conditions. [PERSON] et al. [56] also found that, depending on the additive used, the composition of the gas can be significantly changed. CaO was found to be the most preferred additive in the amount of 30 wt%. The use of CaO increased the H\({}_{2}\) concentration from 25 vol% (without additives) to 65 vol%. At the same time, CO\({}_{2}\) emissions decreased to 0.3 vol% (without additive, CO\({}_{2}\) = 55 vol%). The addition of Fe to the dyeing sludge also had a beneficial effect on the concentrations of H\({}_{2}\) and CO\({}_{2}\) but to a much lesser extent (H\({}_{2}\) concentrations increased to 32%, CO\({}_{2}\) decreased by 48 vol%). CaO and Fe can facilitate the reactions of dehydrogenation and dehydration [107]. When using CaO and Fe, the concentrations of CO and CH\({}_{4}\) increased (from 1.75 to 3 times), which could be associated with cracking reactions, water gas, reforming, and reverse Boudouard reactions. The addition of kaolin to the dyeing sludge also contributed to higher CO and CH\({}_{4}\) yields. In this case, kaolin reduced the yield of solid residue and increased the yield of condensate. In contrast, the addition of 20 wt% Ca-bentonite had a negative impact on the gas quality. CO\({}_{2}\) concentration increased and H\({}_{2}\) concentration decreased compared to dyeing sludge without additives [56]. Fast catalytic co-pyrolysis of bamboo residual and waste lubricating oil (WLO) was studied by [PERSON] et al. [46]. A dual catalytic bed system (MgO and HZSM-5) in CDS analytical Pyroprobe 5200 pyrolyzer was used. The composition of the pyrolysis products was analyzed using the GC/MS system. [PERSON] et al. [46] considered the influence of the pyrolysis temperature, the types of catalysts and their mass ratio, and the WLO content on the distribution of pyrolysis products and the selectivity of aromatic hydrocarbons. Experiments have shown that 600 \({}^{\circ}\)C is the optimum temperature in terms of the yield of condensable organic products, furans, and phenols. When comparing the two catalysts, MgO was found to be more preferable in terms of maximizing the yield of light phenols. MgO also reduced acidity through ketonization and aldol condensation reactions. The minimum yield of acids (2.12%) and the maximum yield of ketones (28.81%) were obtained. An increase in the share of WLO intensified the yield of hydrocarbons (i.e., olefins, alkanes), the maximum yield (70.31%) of which was achieved with an oil percentage of 60%. Waste oil was the main source of hydrogen, which aided the production of aromatic hydrocarbons [46].