**1. Introduction**

Current research studies have been focusing on the procurement of environmentally friendly materials with the aim of resolving the problems created by materials derived from petroleum. Starch is a promising biopolymer used in the production of biocomposite materials because it is renewable, completely biodegradable, and easily available at a low cost. Starch, in the form of its thermoplastic derivate (TPS), has been revealed as an appropriate candidate to be employed as a substitute of synthetic polymers traditionally used for packaging. Starch is not a real thermoplastic polymer, but can be processed after its gelatinization by mixing it with enough water and/or plasticizers [1, 2]. In most investigations the plasticization of the material is carried out by casting a dispersion of starch with glycerol [1, 3].

TPS films are reported to have low permeability to gases, poor water vapor barrier properties, and must resist the tensions arising from their use in packaging [4].

Therefore, improving the resistance of TPS films to traction forces is a factor that must be taken into consideration for their use [5, 6]. The use of reinforcing agents in the starch matrix is an effective means of overcoming these drawbacks and several types of biodegradable reinforce‐ ments such as cellulosic fibers, whiskers, and cellulose nanofibers (CNF) have been utilized to develop new and inexpensive starch biocomposites. Cellulose is the most abundant, renewable polymer in the world; it is found in plant cell walls and it can also be synthesized by some bacteria. Its reinforcing property is remarkable [7]. Basically two types of nanoreinforcements can be obtained from cellulose: microfibrils (or CNF) and whiskers.

Improving the mechanical and water barrier properties by the addition of CNF (extracted from different botanical sources) can depend on the correct dispersion and the generation of an active nanoreinforcement/matrix interface.

This chapter provides the latest advances in green composite materials based on TPS and cellulose fibers and includes information on compositions, preparations, and the properties of "green" composite materials elaborated from TPS and cellulose fibers, with the focus on using undervalued natural resources.
