Wood preservation by low-temperature carbonisation

Pine (Pinus sylvestris L.) wood with dimensions (100 x 10 x 10mm) was thermally treated at 275degreesC in a muffle oven to impart resistance to microbial degradation. Low-temperature carbonised pine resulted in a visually homogeneously treated product with a substantial (about 70% w/w) reduced non-cellulosic carbohydrates content, as compared with untreated pine. These components have been removed or have been partly converted into hydrophobic polymerisation products, which results in reduced water absorption in air of different relative humidity (RH) for carbonised pine. The flexural strength at high RH and after immersion in water of carbonised wood is comparable with untreated and creosote impregnated wood. However, at lower RH the carbonised wood is less strong. Only trace amounts of polycyclic aromatic hydrocarbons (PAHs) and other phenolic compounds could be detected both in water leached from carbonised wood and untreated wood. Furans, mainly 5-hydroxymethylfurfural, have been demonstrated to leach in substantial amounts in the water from carbonised pine. An accelerated decay test in soil showed that low-temperature carbonisation of pine resulted in a product with considerably enhanced durability, as compared with untreated wood. Resistance of carbonised wood against environmental decay was similar or even better than creosote impregnated wood. (C) 2003 Published by Elsevier B.V.