Development of new wood-based thermal insulating material by semi-carbonization treatment of shiitake waste mushroom bed

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K06162
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40020:Wood science-related
• Research Institution: Iwate University
• Principal Investigator: Sekino Noboru 岩手大学, 農学部, 教授 (30171341)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 廃菌床 / 熱伝導率 / 熱伝導モデル / 半炭化 / 圧縮乾燥 / 機械的性質

Outline of Final Research Achievements

To explore the possibility of using the waste mushroom bed as a thermal insulating material, the thermal conductivity, strength, and the mechanisms of the thermal insulation were investigated. When the waste mushroom bed was dried in its original size resulting in a density of about 200 kg/m3, the thermal conductivity was 0.05 W/mK, but the strength was less than half that of the insulation fiberboard. Investigating the relationship between the improvement of thermal insulation and the decrease in strength due to semi-carbonization, it was found that the strength was halved to obtain a decrease in thermal conductivity of about 15%. From this result, it was judged that semi-carbonization to a waste mushroom bed with low strength was unsuitable, and compression drying was adopted as an alternative method. It was found that the waste mushroom bed with a density range of 200 to 600 kg/m3 obtained by compression drying had a thermal conductivity almost equal to that of wood.

Free Research Field

木質材料学

Academic Significance and Societal Importance of the Research Achievements

本研究ではミズナラチップを菌床とするシイタケ収穫後の廃菌床を圧縮乾燥させ、その密度と熱伝導率の関係を調べ、その関係が木材とほぼ同様であることを明らかにした。廃菌床は、シイタケ収穫により木質の約7割の質量損失が生じ、菌糸と腐朽残渣の混在体となっている。これを圧縮乾燥した成形体が木材と同等の断熱性能を発揮したことは、廃菌床の有効活用に資する知見と言える。また、熱伝導モデルの適用により、熱橋となる実質の熱伝導率の大小関係（木材＜廃菌床（腐朽残渣+菌糸）＜菌糸）を得ており、新たな知見として学術的な意義を持つと言える。