Wood, a versatile and natural material, originates from trees and forms the bulk of their structure. It is a complex organic substance. Understanding its fundamental chemical composition provides insight into its varied properties and applications.
The Core Elemental Trio
Wood’s dry mass is predominantly composed of three chemical elements: carbon (C), hydrogen (H), and oxygen (O). Carbon forms the foundational backbone of all organic molecules within wood, comprising approximately 50% of its dry weight.
Hydrogen and oxygen are also abundant, making up about 6% and 44% of wood’s dry mass, respectively. These elements are integral components of the organic structures, binding to carbon to create the various compounds that give wood its characteristic strength and flexibility. Their presence and arrangement within these molecules significantly influence wood’s physical and chemical properties.
Minor Elements and Trace Minerals
Beyond the primary elements, wood also contains nitrogen (N) and various trace minerals. Nitrogen accounts for less than 1% of wood’s dry weight. These elements, such as potassium, calcium, magnesium, phosphorus, and sulfur, are absorbed by the tree from the soil.
These elements are not primarily structural components of the wood itself. Instead, they play supportive roles in the living tree’s metabolic processes and growth. For instance, calcium contributes to cell wall formation, while phosphorus and magnesium are involved in energy transfer and enzyme activation during the tree’s development.
From Elements to Wood’s Structure
The core elements of carbon, hydrogen, and oxygen combine in specific arrangements to form the major organic macromolecules that define wood’s physical characteristics. Cellulose is a primary structural component of wood, forming long, strong fibers. This polysaccharide, made of repeating glucose units, provides wood with its tensile strength and rigidity.
Hemicellulose, another polysaccharide, is present, though it is more branched and has a lower molecular weight than cellulose. It acts as a binding agent, helping to connect the cellulose fibers. Lignin, a complex polymer, serves as a natural glue, embedding and stiffening the cellulose and hemicellulose components, imparting compressive strength and resistance to degradation.
Wood also contains a significant amount of water, although it is not a structural element itself. The water content can vary greatly, ranging from less than 10% in kiln-dried wood to over 200% in freshly cut timber. This water content influences wood’s weight, dimensional stability, and susceptibility to decay.