## 1 Introduction
### Technologies of the Use of Wood for Energy Purposes  
Electricity generation from biofuels is possible in two ways: either in a water Rankine cycle, which receives heat from the furnace to burn biofuel (including blended with coal [23; 24]); or in Brayton and combined cycles, in which the fuel is the combustible gas obtained by pyrolysis or gasification of biofuel. The efficiency of the options depends to a significant extent on the capacity of the unit. As a rule, the water Rankine cycle is economically justified for capacities of the order of several MWs to several tens of MW [25; 26]. It is difficult for gasification technologies to compete with combustion technologies in this area (although some authors suggest using gasification with small gas turbines [27; 28; 29]). However, for smaller capacities (up to 1 MW), which are of most interest in terms of creating autonomous energy systems, gasification turns out to be a promising way to obtain electricity from biofuels [26; 30]. In some cases, it is possible to arrange the organic Rankine cycle, even at small capacity plants [31; 32]. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**A Federal Subject of the** & & & & & \\
**Russian Federation** & & & & & \\ \hline Irkutsk region & & & & & \\ Manufacturing & 35.7 & 4.8 & 0.2 & 8.1 & 48.8 \\ Waste products & 11.8 & 3.8 & 0.4 & 1.0 & 17.0 \\ \hline Buryatiya & & & & & \\ Manufacturing & 3.0 & 0.3 & \(<\)0.1 & 0.4 & 3.7 \\ Waste products & 1.0 & 0.2 & \(<\)0.1 & \(<\)0.1 & 1.2 \\ \hline Zabaykalsky Krai & & & & & \\ Manufacturing & 1.7 & 0.2 & \(<\)0.1 & 0.0 & 2.0 \\ Waste products & 0.6 & 0.2 & \(<\)0.1 & 0.0 & 0.8 \\ Baikal region, total & & & & & \\ Manufacturing & 40.4 & 5.3 & 0.2 & 8.5 & 54.5 \\ Waste products & 13.4 & 4.2 & 0.4 & 1.0 & 19.0 \\ \hline \hline \end{tabular} Notes: PP—plywood production, PPP—pulp and paper products.  
\end{table} 
Table 4: Estimate of wood waste volumes in the Baikal region, million m\({}^{3}\)/year. In this paper, we consider electricity production based on the gasification of biomass rather than its direct combustion. The reasons for this are higher efficiency of biomass for low power plants [33] and fewer technical problems associated with slagging and corrosion damage to equipment. Production of liquid biofuels (e.g., stabilized pyrolysis liquids [34]) suitable for combustion in diesel generators (usually in a mixture with the specification fuel [35]) is not considered in this study, as more complicated process flow diagrams and chemicals are needed to produce such fuels. The choice of gasification method and heat engine type depends on many factors. Biofuels generally have a low calorific value (compared to fossil fuels), which is why their thermochemical conversion does not allow achieving high temperatures. In this connection, the raw combustible gas obtained from the gasification of biofuels often contains significant amounts of tar products (up to several g/Nm\({}^{3}\)), which can adversely affect the durability and reliability of gas engines (both internal and external combustion ones). Therefore, raw gas usually needs additional treatment (including filtration, adsorption, water flushing, and thermal purification [36]). Gasification processes are known that produce gas with a low content of tar products: for example, the downdraft process (tar content in the produced gas is of the order of tenths of g/Nm\({}^{3}\)); and multi-stage processes (less than 0.1 g/Nm\({}^{3}\)). Quality requirements for gas for internal combustion engines are given in [37]: according to these data, the tar content should not exceed 0.1 g/Nm\({}^{3}\). External combustion engines are less demanding in terms of gas purity, as the combustion of gas together with tar takes place in an external heat exchange chamber. In this case, gas combustion is preferable to heating by combustion products of biofuels because this reduces the pollution of heat exchange surfaces by fly ash. Nevertheless, the formation of tar deposits and their coking on the outer surface is not excluded.