## 4 Energy Efficiency Assessment of Wood Fuel Gasification  
In order to estimate gasification efficiency, we used the limit parameters of the process, i.e., the maximum characteristics that are sought for in optimization of technological modes with a given fuel composition. For example, a performance indicator of this kind can be the maximum efficiency of gasification process in terms of thermodynamic constraints. However, to calculate it, we need to know the thermodynamically achievable composition of the resulting syngas that, in turn, depends on the parameters of the technological process. We propose to evaluate the efficiency of gasification using dimensionless criteria. The first criterion is widely used cold gas efficiency (CGE) of the gasification process, equal to the ratio of the heat value of the generator gas to the heat value of origin solid fuel [45]. The second criterion that is used in this paper is the criterion of the process autothermality, which is equal to the ratio of the heat released during \"ideal\" gasification to the heat required for the transition of the reaction mixture to the autothermal (or allothermal) mode, i.e.,: \(C_{g}=q_{g}/q_{h}\). \"Ideal\" gasification means the most complete conversion of the organic matter of the fuel into fuel gas (carbon monoxide and hydrogen) by the reaction:  
\[\mathrm{CH_{h}O_{o}S_{s}N_{n}+\left(\frac{1}{2}+s-\frac{o}{2}\right)O_{2}\ =\ \mathrm{CO}+\frac{h}{2}H_{2}+sSO_{2}+\frac{n}{2}N_{2}}\]  
Therefore, the heat released during the gasification process, \(q_{g}\), will be equal to the difference between the heat value of the fuel (which can be found using the known empirical correlations based on the elemental composition) and the heat value of the syngas produced by the above reaction:  
\[q_{g}\ =\ -\Delta H^{0}_{comb,CH_{h}O_{o}S_{s}N_{n}}+\Delta H^{0}_{comb,CO}+ \frac{h}{2}\Delta H^{0}_{comb,H_{2}}\]  
The value \(q_{h}\) is sensible heat that is required to increase temperature of the fuel and gasification agent from the initial values (fuel temperature \(T_{f}\) and air temperature \(T_{air}\), respectively) to the ignition temperature (\(T_{ign}\)) of the most active component of the volatile fuel (hydrogen was chosen with \(T_{ign}=900\) K). Thermochemical calculations are carried out in terms of enthalpy changes, therefore, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Products**} & \multicolumn{4}{c}{**Year**} \\ \cline{2-5}  & \multicolumn{2}{c}{**2018**} & \multicolumn{2}{c}{**2030 (Forecast)**} \\ \hline  & **Production** & **Waste** & **Production** & **Waste** \\ \hline Logging & 238.6 & 53.9–82.1 & 230.5–286.1 & 52.1–98.4 \\ Lumber & 28.5 & 13.1–23.9 & 62.1–69.5 & 28.6–62.6 \\ Plywood & 4.2 & 6.5–8.0 & 5.1–5.9 & 7.9–11.2 \\ Tare & 0.4 & 1.1 & 0.5–0.8 & 1.4–2.2 \\ Cellulose & 38.8 & 4.7 & 43.4–63.3 & 5.2–7.6 \\ Wood Pulp & 6.3 & 4.4 & 6.8–10.5 & 4.8–7.3 \\ Total & 316.8 & 83.7–124.2 & 348.4–436.1 & 100.0–189.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Waste generation (fuel resource) in the Russian timber industry complex in 2018 and 2030, mln m\({}^{3}\). the heat of phase transitions (moisture evaporation, ash melting) and the release of volatiles is very simple and fairly accurately taken into account in the heat balance [46]. The sensible heat of the organic mass of the fuel is determined by the difference in the total enthalpies of combustion products at the initial temperature and the accepted ignition temperature:  
\[q_{h}\ =\ H_{air}(T_{ign})+H_{grad}(T_{ign})+H_{ash}(T_{ign})-H_{air}(T_{air})-H_{ prod}(T_{f})-H_{ash}(T_{f})\]  
where \(H_{air}\) is the enthalpy of air, \(H_{ash}\) is the enthalpy of ash, \(H_{prod}\) is the enthalpy of combustion products. Thermodynamic analysis of the efficiency of gasification using similar models was carried out in [47; 48; 49; 50], where other methods were proposed for assessing the efficiency of solid fuel gasification based on thermochemical relations.