Forest thinning is a way to make room for the growth of remaining trees, and the thinned wood can serve as a fuel for bioenergy in order to combat climate change. Using thinned wood for bioenergy can substitute for fossil fuel energy, resulting in potential carbon benefit. Since not all thinned wood can be transported out of the forest for processing, the extraction ratio (extraction volume/thinning volume) is an important variable for determining the net carbon benefit. This study investigated 52 forest-thinning sites in Taiwan. The extraction ratio was estimated to explore the benefit of thinned wood used as bioenergy. Cross analysis was adopted to find the relationships between site/species attributes and extraction ratio. The factors included age class, thinning method, land use classification, and species. Key variables included thinning volume, extraction volume, and extraction ratio. Statistical analysis was then applied to identify the significant differences. The analysis shows that the extraction ratio of thinned wood is 57.12%. The research outcomes could provide valuable information for green-energy policy making in Taiwan.