Biodegradable polymers can originate from biomass or petroleum-based and can be classified as green polymeric matrices.14 It is essential to differentiate biodegradable polymers from biopolymers because the origin of the raw material can vary. For instance, poly(caprolactone) (PCL) is a petroleum-based polymer but is completely biodegradable and thus can be referred to as green matrix. These polymers can be degraded by anaerobic and aerobic biological processes, which mainly produce carbon dioxide, water, and biomass.13 Biopolymers (bio-based polymers) are con­sidered biodegradable but not all biodegradable polymers are biopolymers. Rein­forcement of the biodegradable materials with natural fibers give improved material properties, desired in various applications without compromising biodegradability. Figure 9.5 shows the life cycle of biodegradable polymers, which includes conser­vation of fossil resources, water and CO2 production. The rate of biodegradation depends on humidity, temperature (50-70°C), amount and type of microbes.

Polymers from renewable resources have attracted tremendous amount of atten­tion over two decades. The increasing appreciation for biopolymers is predominant­ly due to: environmental concerns, and the rapid petroleum resources depletion.14 Figure 9.6 presents the classification of polymers in four different groups.1115 All the three groups of polymer are derived from renewable resources except the last group, which is from petroleum products.11 Generally, biopolymers can be classified into three groups: (1) natural polymers, like starch, protein and cellulose; (2) synthetic polymers from natural monomers, such as polylactic acid (PLA); and (3) polymers from microbial fermentation, such as polyhydroxybutyrate (PHB).14

Numerous new polymer materials were developed from renewable resources, such as starch, which is a natural polymer. Other biopolymers are poly lactic acid from fermentable sugar and polyhydroxyalkanoate (PHAs) from vegetable oils next to other bio-based feedstocks.16