Chapter 1
An Overview of Methods and Standards

Biocomposites are considered the next-generation materials as they can be made using natural/green ingredients to offer sustainability, eco-efficiency, and green chemistry (1-3). Nowadays, biocomposites are being utilized by numerous sectors, which include automobile, biomedical, energy, toys, sports, and others.

An effort has been made to provide a comprehensive assessment of the available green composites and their commonly used in order to make materials capable of meeting present and future demands. Various types of natural fibers have been investigated with polymer matrixes for the production of composite materials that are on par with the synthetic fiber composite. Also, the requirements for green composites in various applications from the viewpoint of variability of fibers available and their processing techniques have been detailed (4).

1.1 History of Biodegradable Plastics

In the late 1980s, biodegradable plastics came into use. However, these came to be misapplied in a number of situations. The misapplication of inappropriate or incompletely developed technology led to products which often did not meet performance claims and expectations. The so-called first generation technologies often lacked one or more of the following issues (5):

• Rate or extent of biodegradation, primarily due to limitations of starch incorporation,
• Necessary physical properties and related characteristics
• An economical means to effectively and efficiently manufacture starch-based blends,
• Intermediate product compatibility with conventional plastics product conversion processes, and
• Lower limits on film thickness caused by the use of non-gelatinized starch materials.

The synthesis, processing, and technology of renewable polymers has been reviewed (6-27). Furthermore, the state-of-the-art for food packaging applications has been reviewed (28-32). Using biomass for the production of new polymers can have both economic and environmental benefits (33).

Biomass-derived monomers can be classified into four major categories according to their natural resource origins (34):

1. Oxygen-rich monomers including carboxylic acids, e.g., lactic acid succinic acid, itaconic acid, and levulinic acid, but also ethers, such as furan,
2. Hydrocarbon-rich monomers including vegetable oils, fatty acids, terpenes, terpenoids and resin acids,
3. Hydrocarbon monomers, i.e., bio-olefins, and
4. Non-hydrocarbon monomers such as carbon dioxide.

Carbon dioxide is an interesting synthetic feedstock, which can be copolymerized with heterocycles such as epoxides, aziridines, and episulfides. In 1969, Inoue reported the zinc catalyzed sequential copolymerization of carbon dioxide and epoxides as a new route to poly(carbonate)s (9, 35). The reaction is shown in Figure 1.1.

Figure 1.1 Reaction of carbon dioxide with epoxides (35).

Plants produce a wide range of biopolymers for purposes such as maintenance of structural integrity, carbon storage, and defense against pathogens as well as desiccation. Several of these natural polymers can be used by humans as food and materials, and increasingly as an energy carrier. Plant biopolymers can also be used as materials in certain bulk applications such as plastics and elastomers (36).

Lignin, suberin, vegetable oils, tannins, natural monomers like terpenes, and monomers derived from sugars are typically natural precursors for bio-based industrial polymers. Glycerol and ethanol also play a potential role as future precursors to monomers (37).

1.2 Green Chemistry

The principles and concepts of green chemistry are the subjects of several monographs (38-47). Recent progress in enzyme-driven green syntheses of industrially important molecules has been summarized (48). Studies in biotechnological production of pharmaceuticals, flavors, fragrance and cosmetics, fine chemicals, as well as polymeric materials (49) have been documented. Biocatalysis is a transformational technology uniquely suited to delivering green chemistry solutions for safer, efficient, and more cost-effective chemical synthesis.

The different catalytic processes for the conversion of terpenes, triglycerides and carbohydrates to valuable chemicals and polymers have been reviewed (50).

A basic task of green chemistry is to design chemical products and processes that use and produce less hazardous materials. The term hazardous covers several aspects, including toxicity, flammability, explosion potential and environmental persistence (51).

The synthesis of maleic anhydride illuminates a possibility of multiple pathways. Maleic anhydride can be synthesized both from benzene and from butene by oxidation. In the first route, a lot of carbon dioxide is formed as an undesirable byproduct. Thus, the first route is addressed as atom uneconomic. In Table 1.1, some uneconomic and economic reaction types in organic chemistry are opposed.

Table 1.1 Atom uneconomic and economic reaction types.

There were in total 12 basic principles in green chemistry (52-55). These principles are summarized in Table 1.2.

Table 1.2 Basic principles of green chemistry (53).

Ensure that all material and energy inputs and outputs are as inherently nonhazardous as possible.

Better prevent waste than cleanup.

Minimize energy consumption and materials.

Maximize efficiency of mass, energy, space, and time.

Products, processes, and systems should be output pulled rather than input pushed.

Embedded entropy and complexity must be viewed as an investment when making design choices on recycle, reuse, or beneficial disposition.

The design goal should be targeted durability.

Unnecessary capacity or capability is not desirable.

Material diversity in multicomponent products should be minimized.

Development of products, processes, and systems must consider energy and materials flows.

The design should consider a commercial afterlife.

Material and energy inputs should be renewable.

Recently, the above-mentioned concept was extended (56). The special volume on green and sustainable chemistry and engineering has fourteen papers that were considered relevant to the present day issues and discussion, such as adequate use of raw materials and efficient energy, besides considering renewable sources for materials and energy; and changing economical canons towards circular economy. Businesses, governments and societies are facing a number of challenges along the pathway to sustainability for the well-being of future generations. Chemicals are ubiquitous in everyday activities. Their widespread presence provides benefits to societies' well-being, but can have some deleterious effects. To counteract such effects, green engineering and sustainable assessment in industrial processes have been gathering momentum in the last thirty years. Green chemistry, green engineering, eco-efficiency, and sustainability are becoming a necessity for assessing and managing products and processes in the chemical industry. Fourteen articles have been discussed, related to sustainable resource and energy use (five articles), circular economy (one article), cleaner production and sustainable process assessment (five articles), and innovation in chemical products (three articles) (56).

Catalytic processes from the viewpoint of green chemistry include catalytic reductions and oxidations methods, solid-acid and solid-base catalysis, as well as carbon-carbon bond formation reactions (57).

Novel concepts and techniques such as bio-inspired polymer design, synthetically-inspired material development are now considered to contribute to the development of natural monomers and polymers as a sustainable resource. These concepts and techniques that integrate materials synthesis, process and manufacturing options with eco-efficiency have been documented (58-62).

1.2.1 Genetic Engineering

The direct production of novel compounds in biomass crops in order to produce bioenergy as a coproduct seems to be a promising way to improve the economics of transgenic plants as biofactories (63).

Genetic engineering of plants may be used for the production of novel polymers and basic chemicals. These methods may help to alleviate the demands for limited resources and provide a platform to produce some desired compounds in bulk quantities.

Recent advances in enhancing the production of novel compounds in transgenic plants consist of a multigene transformation and the direction of the biosynthetic pathways to specific intracellular compartments.

Basically it appears feasible to produce interesting proteins, such as spider silk or collagen, novel carbohydrates, and biopolymers using transgenic plants. These compounds could replace petroleum-based plastics (63). However, there are pro and con arguments. For example, if transgenic...