Using Kraft Black Liquor as a Wood Preservative

AbstractUnder appropriate conditions, wood is degraded easily due to the diversity of biological agents. One way to protect wood from these agents is to impregnate the wood with chemicals. However, increasing environmental pressure has caused a restriction on the use of toxic chemicals. In recent years, researchers have been looking for environmentally friendly preservative chemicals, modification and impregnation methods to develop wood properties such as the durability, water absorption, and dimensional stability. In this study, the remaining Kraft black liquor was employed to Scots pine sapwood (Pinus slyvestris L.) specimens as a wood preservative to enhance the wood durability against biological agents. The black liquor used in this study was obtained from the pre-hydrolysis Kraft pulping process. Various concentrations were used for black liquor; 2.5%, 5%, and 7.5% respectively. The test specimens were impregnated in a small scale impregnation container using a vacuum of 650mm/Hg for 30 mins. Both test and control wood samples were tested for resistance to brown rot fungus; Coniophora puteana and Poria placenta. Six weeks of exposure to brown rot fungus, C. puteana and P. placenta, resulted in noteworthy weight loss of control samples compared to test samples. After six weeks of exposure to both fungi, the weight loss of control samples were more than 25%, while the weight loss of test samples were less than 3%. The most effective results were obtained at 5% concentration. These results indicate that black liquor enhances the durability of Scots pine sapwood. It can be stated that the carbohydrate degradation products, resin and fatty acids, extractives, and the inorganic materials in the black liquor used in the process showed inhibiting fungal activity