Introduction

Cellulose represents a naturally occurring linear macromolecular chain of 1–4-linked β-D-glucopyranose and exhibits great chemical variability and potential in applications. The cell walls of all plants contain fibers of cellulose. Cellulose has long been harvested as commercial fibers from the seed hairs of cotton (over 94% cellulose), as bast fibers (60-–80% cellulose) from flax, hemp, sisal, jute and ramie or as wood (40–55% cellulose), which is a common building material or is used as a source for purified cellulose. The chemical compositions of some known species are collected in Table 1.1, which, when purified, serve as cellulose sources. Wood represents a composite material with cellulose as a major part combined in excellent form with lignin and hemicelluloses, creating a unique high-strength and durable material, and recently came again into focus as a renewable energy resource.