# Research Trends and Future Direction for Utilization of Woody Biomass in Japan
## 7 Environmental Impact Assessment of Woody Biomass Utilization
### GHG Emission Reduction Effect of Woody Biomass Power Generation  
The reviewed papers did not employ uniform estimation methods; instead, they utilized four distinct approaches: substitution effects, energy flows, life cycle assessment (LCA), and IO analysis. Substitution effect and energy flow are relatively simple estimation methods. The substitution effect calculates the GHG emissions produced by fossil fuels replaced by woody biomass, using it as the GHG emission reduction resulting from woody biomass utilization. Energy flow considers fossil fuel consumption in the process from woody biomass raw material collection to energy utilization, building upon the calculations made in the substitution effect. In contrast, LCA and IO analysis are more comprehensive estimation methods. LCA evaluates the environmental impact of the entire process, from raw material mining to the final disposal of waste, whereas IO analysis estimates the environmental impacts from an economic perspective by analyzing the inputs and outputs of a target sector.  
The reduction in GHG emissions resulting from the utilization of wood biomass power generation is presented in Table 10 (where multiple scenarios exist, each scenario is considered as one case). Due to variations in the estimation methods employed by different studies, the calculated GHG emission reductions exhibit a wide distribution, ranging from \(-17.29\) to \(131.87\) kg-CO\({}_{\text{2 eq}}\)/GJ. Among them, Case 1 in Table 10 calculates the utilization of woody biomass power generation using thinned wood, with a power generation efficiency of \(20\%\), and finds that the GHG emission reduction is negative. In other words, woody biomass power generation results in greater GHG emissions than existing fossil energy power generation. This situation arises because Case 1 assumes the use of thinned wood as fuel with low power generation efficiency. Case 3 in Table 10 explores a scenario in which the power generation efficiency is increased to \(30\%\) under the same conditions as in Case 1, resulting in a positive GHG emission reduction [73]. In addition, Case 11 in Table 10 conducted an assessment of the construction and operation of the woody biomass power plant and found that, compared with traditional thermal power plants, the GHG emissions generated by the woody biomass power plant would be reduced by \(25.08\) kg-CO\({}_{\text{2 eq}}\)/GJ [74]. In the field of CHP, Cases 9 and 10 in Table 10 used different  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Case No.**} & \multirow{2}{*}{**Region and Year**} & \multicolumn{6}{c}{**Total Impact [mil. JPY]**} & \multicolumn{6}{c}{**Economic Impacts**} \\ \cline{3-10}  & & **Total** & **Multiplier** & **Value-** & **Add** & **Multiplier** & **Income** & **Multiplier** & **Per Unit** [mil. JPY/l] & **Reference** \\ \hline
6 & Nishiwaga town, Iwate & 7.8 & 1.28 & N.A. & N.A. & N.A. & N.A. & N.A. & [71] \\  & Meniwa city, Okayama & 179.5 & 1.50 & 102.1 & 1.50 & N.A. & N.A. & 75.71 & [72] \\  & Meniwa city, Okayama & 203.9 & 1.50 & 117.3 & 1.50 & N.A. & N.A. & 108.85 & [72] \\
8 & Meniwa city, Okayama & 123.9 & 1.60 & 60.3 & 1.80 & N.A. & N.A. & 248.95 & [72] \\  & Pref., 2015 & 1234.0 & N.A. & N.A. & N.A. & N.A. & N.A. & N.A. & [66] \\
10 & Western Tottori Pref., 2017 & 2905.0 & N.A. & N.A. & N.A. & N.A. & N.A. & N.A. & [66] \\
11 & Western Tottori Pref., 2017 & 2905.0 & N.A. & N.A. & N.A. & N.A. & N.A. & N.A. & [66] \\
12 & Kamaishi City, Iwate & 1.9 & 1.23 & N.A. & N.A. & 0.3 & N.A. & 66.08 & [64] \\ \hline  & & & & & & & & & \\  & & & & & & & & & \\ \end{tabular}
\end{table}
Table 9: _Cont._research methods, and estimated GHG emission reductions are 202.44 kg-CO2 eq/GJ and 44.21 kg-CO2 eq/GJ, respectively. The evaluation results for Case 10 show a larger GHG emission reduction effect, surpassing any of the cases listed in Table 10. This difference may be attributed to Case 10 not considering the GHG emissions generated during the resource collection process [75].