Chemical Changes and Environmental Issues of Heat Treatment of Wood

Abstract

The paper gives an overview of chemical changes during heat treatment of wood and their influence on environment. Wood is one of the most used building materials because of its physical and technological properties. Various procedures improve its properties, and due to its environmental acceptability, heat treatment of wood is one of the most commonly used. Heat treatment causes changes in the cell walls and degradation of the main components of the wood structure (cellulose, hemicelluloses, lignin) and extractives. Hemicelluloses, as the most unstable components, are broken down first, followed by cellulose and finally lignin. Degradation results in a change in chemical composition and chemical reactions of colour change causing a technological problem because wood processing tends to make the colour as uniform as possible. The uniformity of colour and the desired colour tone are obtained by the process of steaming and thermal modification. The processing temperature is the most important factor that causes all the changes. Due to its wide use, need has arisen to investigate the ecological consequences of such a heat treatment process, as well as the impact of harmful substances and types of compounds released during the process and their toxicity.