列状間伐による木質バイオマス利用の可能性 : 東京農業大学大桁山分収林を事例として
| Autor: | Satoshi, Yoshino, Yabe Kazuhiro, Sato Takayoshi |
|---|---|
| Jazyk: | japonština |
| Předmět: | |
| Popis: | 木質バイオマスは,石化資源にかわる再生可能な資源の一つであり,エネルギー問題や環境問題など様々な側面から注目されている。木質バイオマス利用を考える際に,林地残材の活用が重要である。しかし,素材価格の低迷,高額な素材生産費,容易でない林地残材の集荷などの問題から,林地残材は有効利用されていない。今後は,資源の供給や活用方法だけでなく,素材価格と素材生産費の関係に注目し議論する必要がある。列状間伐は低コストかつ集約的な間伐である。また,林地残材が作業道付近に散在するので,列状間伐による木質バイオマスは,V1 (素材市場や製材工場への生産量),V2 (作業道付近の利用可能な木質バイオマス量),V3 (搬出不可能な木質バイオマス量)に分けられると考えた。そこで,東京農業大学大桁山分収林で行われた列状間伐および間伐材の流通を事例に,素材価格と素材生産費から木質バイオマス利用の可能性を考察した。分析の結果,東京農業大学大桁山分収林における対象林分(3.98ha)からの間伐材は,V1が213.138m^3で,V3をほぼ0であると仮定するとV2が189m^3となった。素材生産費の内訳は,素材の伐採・搬出・運材費が1,535,494円,作業道開設費は1,791,000円であった。しかし,作業道開設と間伐に対する補助金を活用したので,素材生産費の負担は1,607,594円(7,543円/m^3)となった。V1は収益がマイナスの材と,収益が4,560円/m^3 (久保山(2009)による他のエネルギーとの競争が可能な価格)以下の材と,収益が4,560～13,300円/m^3の材,三つに分類できた。V2材とV1材の一部を木質バイオマスとして利用すると仮定すると,1m^3あたりの素材生産費が下がり,マイナス材が減少すると推定した。本事例における木質バイオマス利用として,木質バイオマス資源への全利用という経営戦略が可能性の一つとして考えられる。 Wood biomass is a renewable resource, which substitute of the petrifaction resource, and now it is receiving attention because of multiple functions, not only an energy resource but also other functions such as environment conservation. But at the practical phase, the wood biomass is difficult to use because yarding of slash is not easy, the cost and income makes reflection each other, and those resources were disposed the forest. So for the sufficient use of wood biomass, we should consider the supply and use method with strategy that considers cost and income. Line thinning is a consolidated thinning method and its cost is low, while slash lies scattered in the vicinity of the yarding road. Thus, it was considered that wood biomass from line thinning could be classified into V1 (the estimated volume shipped to the market), V2 (the estimated wood biomass left on the skidding road), V3 (volume of log remaining in the stand). So the study focuses on the possibility of wood biomass usage in terms of cost and income in the case of line thinning in the shared forest of Tokyo University of Agriculture. The results showed that the estimated total volume of thinned was 402m^3, i.e. V1 was 213m^3, i.e. V2 was 189 m^3 and i.e. V3 was not considered. Total logging cost excluding cost of yarding road construction was calculated to be 1,535,494yen, and the cost of logging road was 1,791,000yen. The final total cost of line thinning was 1,607,594yen (7,543yen/ m^3)which was deleted because of subsidy for the thinning and establishment of yarding road. According to the income by log cluster, V1 was divided into three groups ; the first income was minus, the second income was under 4,560yen (border value of the competition price by other energy that KUBOYAMA (2009) reported), and the third income was between 4,560∼13,300yen. From the site of forest management, we considered the following strategies : The first is that only V1 is used. But if it is, the cost turned out to be more whereas total income decreased. The second is that, for part of V1 and all of V2 for the wood biomass, the thinning cost turned down and the wood group whose income is minus was decreased greatly and other group's income was increased. The third is that all thinned wood is for wood biomass use. If V2 log could be use as wood biomass, total harvesting cost would decrease and minus log would also decrease. In this case study, it was recommended to apply for wood biomass use, a portion of the logs or total logs due to a few high benefit if there are demands on wood biomass. So if we consider the possibility of biomass use by line thinning in this case, it is effective to choose the strategy that wood from line thinning is for total use of wood biomass. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|