Abstract

The Primary goal of pre-incident waste management planning is to prepare a community to effectively manage waste, debris and materials generated by a homeland security incident, including reducing the potential amount of waste generated at the outset. The today’s scenario has drastic increase in the ecowaste management as concerned for environmental health. Conversion of ecowaste into biodegradable polymers has a wide scope in the field of pharmaceutics, packaging and food industries etc. The various ecowaste are recycle by various treatment and utilize in various selective areas like crosselinkingdecrosslinking, depolymerisation in super critical fluid polymers etc. The current study describes various application of ecowaste substance like Egg Shell, Fish Scale, Crab Shell, Wood Fibers, Rice Husk etc. The Food and Agriculture Organization (FAO) estimates that 20%–30% of fruits and vegetables are discarded as waste during post-harvest handling. The development of bio-based polymers is essential, considering the scale of global environmental pollution that is directly linked to the production of synthetic plastics such as polypropylene (PP) and polyethylene (PET). Globally, 400 million tons of synthetic plastics are produced each year, and less than 9% are recycled. The optical, mechanical, and chemical properties such as ultraviolet (UV) absorbance, tensile strength, and water permeability are influenced by the synthetic route. The production of bio-based polymers from renewable sources and microbial synthesis are scalable, facile, and pose a minimal impact on the environment compared to chemical synthesis methods that rely on alkali and acid treatment or co-polymer blending. Despite the development of advanced synthetic methods and the application of biofilms in smart/intelligent food packaging, construction, exclusion nets, and medicine, commercial production is limited by cost, the economics of production, useful life, and biodegradation concerns, and the availability of adequate agro-wastes. New and cost-effective production techniques are critical to facilitate the commercial production of bio-based polymers and the replacement of synthetic polymers

Keywords

Introduction

Waste material involves the collection and disposal of both hazardous and non-hazardous waste from all the sections of a society. Ecowaste management is a burning issue of the day. The Processing of ecowaste can generate energy, reduce the pollution caused by toxins. Formed by incineration, slow down global warming and reduce waste products in landfills and water bodies. The basic aim of today’s study is to reduce the need of Synthetic polymer manufacturing and simultaneously reduce the pollution caused by them. Many Biodegradable polymers from the ecowaste materials are used videly due to their user-friendly nature. Disposal of plastic wastes is a serious environmental problem that we face today. Mass production and increased use of plastics in wide applications in our daily life1,2 have resulted in environmental impact. Consequently, these issues lead to the growing threat of global warming resulting from carbon dioxide emission due to burning of non-biodegradable conventional polymers such as polyethylene, polypropylene, and polyvinylchloride3 . Biodegradable polymers are being developed to be used as an alternative for non-biodegradable polymer materials in a variety of applications4 . The best option for managing non-biodegradable plastic waste is to replace the use of uneconomical non-biodegradable materials for recycling or reuse with biodegradable polymers as they are environmentally friendly5 . Because of the environmental pollution resulting from the use of non-biodegradable materials, studies and developments have increased about biodegradable materials 6. Biodegradable polymers are materials that can work for a limited time before degrading into readily discarded products through a regulated procedure7. They might be made from a variety of wastes or/and bioresources, such as wastes of food, animal, agro-waste as well as other sources such as starch, and cellulose. Bioplastics made from renewable resources are often less expensive than those made from microbial resources prompting producers to concentrate on making bioplastics from renewable resources8. The use of biodegradable polymers has environmental benefits such as regeneration of raw materials, biodegradation and reduction of carbon dioxide emissions that are led to global warming9.  Microorganisms such as bacteria and fungus may consume biodegradable polymers and convert them to H2O, CO2, and methane. The biodegradation process depends on the material’s composition10.

Definition Of Biodegradation

The biodegradation of biodegradable polymers is defined as chemical decomposition of substances, which is accomplished through the enzymatic work of microorganisms that lead to a change in chemical composition, mechanical and structural properties and forming metabolic products, which are environmentally friendly materials such as methane, water and biomass and carbon dioxide. Figure 1 shows biodegradation steps of polymers3 . Extracellular enzymes and abiotic agents such as oxidation, photo-degradation, and hydrolysis depolymerize long-chain polymers and create shorter chains (oligomers) in the first stage20,21. The biomineralization process, in which oligomers are bio-assimilated by microorganisms and then mineralized, is the second stage. Either aerobic and anaerobic degradation can occur. Aerobic degradation takes place in the presence of oxygen producing CO2, H2O, biomass and residue. Anaerobic degradation is carried out in absence of oxygen producing CO2, H2O, CH4, biomass and residue20.

Factors affecting biodegradation

The biodegradation process is affected by various factors including polymer morphology, structure, chemical treatment and molecular weight. (1) Polymer structure: biodegradable polymers have hydrolyzable linkages along the chain of polymer that are exposed to degradation in the presence of microorganisms and hydrolytic enzymes. Polymers with both hydrophobic and hydrophilic structures are more degradable than polymers containing either hydrophobic or hydrophilic structures11. (2) Polymer morphology: enzymes attack the amorphous regions in polymers easily than crystalline regions as amorphous regions molecules are far apart from each other which makes it susceptible to degradation. The enzymatic degradation of polymers is also affected by the melting temperature (Tm) of polymers. Biodegradation of polymers decreases by increasing the melting point of polymers22. Tm ¼ ?H=?S Where, ?H is the enthalpy changes on melting and and ?S is the entropy changes on melting22. (3) Radiation and chemical treatments: cleavage and crosslinking of polymers caused by radicals and/or ions produced by photolysis of polymers with UV and ?-rays irradiation. Oxidation additionally takes place complicating the situation that changes the polymer’s capability for biodegradation11. (4) Molecular weight: the biodegradability of the polymer reduces as the polymer molecular weight increases22.

Biodegradable Polymers

The environment suffers from serious problems from the increasing difficulties of disposing of plastic waste that resist microbial degradation23. Therefore, the researchers tried to produce biodegradable, non-polluting, and environmentally friendly materials24. In recent times, the natural and synthetic origin of biodegradable polymers was produced with good compatibility and biodegradability11. As the biodegradable polymers receive great attention because they degrade into non-toxic and environmentally friendly materials24. Mechanical strength, thermal and electrical properties of common biodegradable polymers and their composites are shown in Fig. 2a–c. Polyglycolide (polyglycolic acid, PGA) has high tensile strength (70–117 MPa). Thermoplastic starch showed low tensile strength (16–22 MPa).

Classification of biodegradable polymers

Biodegradable polymers may be categorized based on their origin and synthesis method, their chemical composition, economic importance, processing method and applications. They are categorized in this study based on their origin24. Biodegradable polymers are classified into two groups based on their origin as indicated in Fig. 3. Natural biopolymers and synthetic biopolymers are made from natural resources and oil, respectively11,18. Natural biopolymers are derived from renewable or biological sources such as animal, plant, marine, and microbial sources, while synthetic biodegradable polymers are manufactured chemically25. Natural biodegradable polymers. All organisms’ growth cycles result in the formation of biopolymers in nature. Polymerization reactions with a chain of enzyme-catalyzed growth from active monomers generated within cells through complicated metabolic processes are included in its production23. They are naturally biodegradable and have good biocompatibility26. Biopolymers directly extracted from biomass. Agricultural waste is a major source for the production of bioplastics, plasticizers and antioxidant additives. The main source of polysaccharides is plant based agricultural waste where biopolymers such as cellulose, starch, and pectin are produced27,28. The use of agro-waste as a feedstock for biodegradable polymer synthesis can reduce both the cost of producing biodegradable polymers and the waste treatment cost. Biopolymers are produced through several methods, namely microbial methods, blending of biopolymers, and chemical methods27. Biopolymers produced from agricultural plant waste have biodegradability, bio-functionality, biostability, They have wide range of chemical and mechanical properties that may be employed in several applications such as food packaging, biomedical applications, skincare, electrical electronics, vehicles and wastewater treatment28. Polysaccharides: Polysaccharides, proteins, and lipids are found in numerous applications in biodegradable products. Potatoes, corn, and rice are basic sources of starch production, where the chemical composition and granules size of starch varies according to the source of production11. As shown in Fig. 4a, starch is a combination of linear (amylose) and branching (amylopectin) poly-(1,4) -?-glucose29. The ratio of amylose to amylopectin has a substantial impact on the physicochemical characteristics of starch30. Starch has poor mechanical properties, low impact resistance, water sensitivity, and brittleness properties. The properties can be improved by reinforcing the starch matrix with fibers or modifying the starch chemically or physically with other biodegradable polymers to enhance its properties24,31. Starch is not completely soluble in water. It is partially soluble in water at room temperature, depending on the proportions of amylose and amylopectin32–34. There are many advantages to starch biopolymers, such as high biodegradation, renewability, and good oxygen barrier properties that make them suitable in some commercial applications such as packaging applications, bags, cosmetics, adhesives, medical applications, and agricultural mulch films3,30,35.One of the most common biopolymers is cellulose29. It contains reactive OH groups in the backbone31. Cellulose is a polysaccharide with a molecular structure that is similar to starch. However, d-glucose units are attached to ?-glycosidic bonds in cellulose. In starch, d-glucose units are linked to -?-glycosidic bonds. As illustrated in Fig. 4b, cellulose consists of polymer chains made up of unbranched ? (1 ? 4) connected D-glucopyranosyl units29. Cellulose is the primary component of lignocellulosic plant cell walls. Hemicellulose, lignin, and other carbohydrate polymers are components of a gel matrix embedded with cellulose which exists in the lignocellulosic materials11. Cellulose and cellulose derivatives are ecologically friendly materials that are widely utilized due to their ability to decay, compatibility with other materials, and regenerate. Because of cellulose’s hydrophilic nature, moisture absorption causes the material’s mechanical characteristics to deteriorate. As a result, cellulose derivatives are created through chemical modification, in which bonds are formed between the reagents and the OH

Biodegradable polymer blends and composites

The main characteristics of biodegradable polymers are their primarily hydrophilic nature, high rate of decomposition, and potentially undesirable mechanical qualities. These properties could be improved by mixing natural and synthetic polymers11,48. Blending polymers is a category of substances where two polymers at least are mixed collectively to produce a new material with various physical properties. The purpose of mixing two or more polymers is to develop a blend that combines each polymer’s preferred properties49. The preparation of biodegradable polymer blends is normally associated with the blending of a thermoplastic resin with biodegradable one. These types of blends are expected to be more biodegradable than conventional plastics50. After the degradation process of the biodegradable materials, the residuals components are more ecologically friendly and do not cause environmental pollution3 .

Natural Fibers

Natural fibers are perfect reinforcing materials for polymer composites (thermoplastics, thermosets, and elastomers). Natural fiber-reinforced polymer composites are gaining popularity due to their excellent mechanical properties and considerable manufacturing benefits, as well as the fact that they provide a solution to environmental contamination. Composites based on natural fibers have better impacts in the industry due to these fibers have high specific properties and low density. They don’t have health hazards because of they are non-toxic51. Natural fibers are renewable materials, relatively high in tensile strength, low-cost, and light52. Natural fibers have become a substitute for nonrenewable and expensive synthetic fibers (glass, carbon and kevlar fibers)53 in different applications because of environmental aspects and their properties as shown in Fig. 554. Natural fibers contain some desirable properties, including high specific strength and modulus, flexibility during treatment, and excellent corrosion resistance53. However they show some limitations such as high anisotropy, moisture absorption, limited compatibility with conventional resins, and inferior homogeneity when compared to glass and carbon fibers55,56. For centuries, natural fibers used in several applications such as clothing, making baskets, ropes and various parts of automobiles54.

Advantages Or Benefits Of Waste Management

1. This Practice is highly lucrative

The journal of Waste management says that the revenues generated by the waste management would top by $60 million by 2018. But there are only a few people who sincerely consider this as an industry into various facets of waste management like recycling and reusing, and reap the benefits.

2. Keeps the environment clean and fresh

Perhaps, the greatest advantages of waste management in keeping the environment fresh and neat. These waste disposal unit units also make the people go disease free as all the resultant waste are properly disposal and taken care of. This is the best effect of proper waste disposal.

3. Saves the earth and conserves energy

This characteristic of waste management includes specifically the recycling aspect. As recycling of waste help in reducing the cutting down of trees. This cutting of trees is mainly done for the production of paper. by using this method, we can be use the recycled waste to make quality papers rather relying on trees

4. Reduces environmental pollution

As explained above, waste management if done in a manner not only eliminate the surrounding waste but also will reduce the intensity of the greenhouse gases like methane, carbon monoxide which is emitted from the wastes accumulated. The depth of the existing landfills and incineration will be curbed thereby cutting down the harmful factor that affect the environment

5. Waste management will help you earn money

Can you believe if  I say that what I have said above is absolutely true ? Yes waste management earn you a few extra bucks every month. Actually there are many companies which will pay you for your waste. Right from old and used bottles to tin cans and e-wastes all kinds of wastes are collected and paid. These wastes are then segregated according to the extent of pollution they cause to the environment and these wastes are recycled accordingly for various purposes. There are also crash course available which will aid you to reuse your trash

Disadvantages Of Waste Management

1. The process is not always cost-effective

Yes, though it may pay cash to the contributors, the truth is this process needs a lot of money, time and land to set up a plant and run. As the amount of waste that is being contributed to the waste product unit increases, so are the no. of plants that process these resource. Setting up a huge factory obviously needs a lot of money, and this management will start fetching yields only in the long run. Hence this is not seen as a short term lucrative investment. While dumping more and more garbage in the landfills cause only $50 per ton, which is exactly triple the cost and thus many of the companies tend to switch over to the landfill method itself.

2. The resultant product has a short life

This is also true since the resulting recycled product cannot be expected to have a durable quality. As the product itself has its origin from a durable quality. As the product itself has its origin from the remains of other trashed waste products and heaps of partially used ones. The recycled product thought is eco-friendly is expected to have a shorter life span than the intended original one.

3. The sites are often dangerous

As the wastes management sites include the landfills to recycling units under its aegis these sites are highly susceptible to fungal and bacterial growth thereby leading to various disease. Even the debris formation will be accelerated by such bacterial growth, which makes it totally unsafe for the worker who work there. It also causes a widespread pollution and release harmful chemicals. These chemicals, when mixed with drinking water or any other consumable item pose a high amount of danger to the human health.

4. The practices are not done uniformly

Still, a large scale of these waste management practices are done only as a small scale process and is mostly confined to residential homes, schools and colleges and is not practiced on a uniform manner in large industries and conglomerates. It is not even practiced globally, as the global level consists of curbing spills, ocean disposal and decreasing the tree felling. Some of them are briefly describe below

1. Fish Scales

Fish Scales are the main waste materials of fish. It is the main source of protein rich in organic fertilizers. Microneedles produced from biopolymers films are extracted from fish scales of Tilapia (Oreochromiss sp.) using micromolding techniques.

2. Crab Shells

The crab shell waste is also utilized for Chitin production. Chitin has high Antimicrobial activity against a wide variety of pathogenic and breakdown microorganisms. Recycled crab shell waste exhibit antimicrobial activity against medically significant pathogens. Microparticles present in crab shell have anti-inflammatory activity that could lead to the development of novel prevention and therapeutic stratagies for those who suffer from inflammatory bowel disease.

3. Egg Shells

Discarded egg shell has no value in the date, but often used as plant fertilizers because they contain calcium. Making egg shell fertilizers are inexpensive and environmental friendly. Calcium obtained from shell can raises or  neutralize the pH level of overly acidic soil. It ismainly used as natural calcium carbonate source in combination with  Hyaluronan as beneficial additive for bone graft material. It also used for extraction and quantification by ELISA of organic matrix proteins. In Pharmaceutical industry used as pharmaceutical excipients, widely used as Diluent to control drug release from the tablet.

4. Citrus Peels

Because of the increase in the threat of infectious disease, the need of the hour is to find some natural agents with novel mode of actions. Most of the citrus fruits peels are thrown out into the environment as a waste. Many citrus pills are used against pathogens causing GIT distraction orders. It also used for extraction of pectin. Recently it was found for its antimicrobial activity.

5. Banana Peel

Whole banana is used for the nutritional value. Banana peels have the Antibacterial activity against Gram positive & Gram Negative bacteria. In Pharmaceutical industry used as binding and suspending agent. Also acts as biosorbents to reduce the copper contents in the textile industry waste water.

6. Wood Fibers

Chemically fibers consist of Cellulose & Lignin, so it used as a source of cellulose and lignin. Which widely used as filter aid and filter medium for filtration purpose.

7. White Rice Husk

Excipients in tablet manufacturing which is obtained from Rice Husk. Sodium dioxide obtained from Rice husk as a excipient. It is also utilize as a Absorbent for removing heavy metals from water.

Structure and composition of natural fibers

Natural fiber cell walls are made up of three layers: a main cell wall, a secondary cell wall, and an intermediate cell wall known as lumen59. Fig. 6b depicts the structural organization of a natural fiber cell wall52,59,76. This structure is known as microfibril63. During cell formation, the wall of the primary cell is the first layer formed. Secondary walls S1, S2, and S3 are the three layers that make up the second cell wall77. The lumen layer is responsible for the transportation of water78. The cell walls are formed of a semicrystalline cellulose microfibril, hemicellulose, lignin, wax, pectin and water-soluble compounds63,77. The physical properties of the fiber are connected to the inner structure and components of the plant material that is being used. The fiber of plants is lignocellulosic structures which are consist of hemicelluloses, cellulose, and lignin, as well as pectin, protein, wax, ash, tannins, and inorganic salts59. These components are vary according to the fibers sources, growth conditions, age of plant and processes of digestion59,63. The chemical composition of some of the common natural fibers are presented in Table 159,77,79. Cellulose content of fibers is the most important factor in determining their characteristics and mechanical performance when utilized as reinforcement in composites. In contrast to cellulose, an increase in non-cellulose components causes a decrease in fiber strength and modulus, which has severe consequences for composites reinforced with natural fibers59.

Surface modification of natural fibers

Natural fibers have a variety of drawbacks in reinforcement composites, including poor compatibility with the polymer matrix due to the hydrophobic character of the polymer matrix and the hydrophilic character of the fibers. Their moisture absorption, and dimensional stability are considered as main limitations63,80. The high wettability can be attributed to the existence of OH groups, and polar groups. The mechanical properties of natural fibers decreased when the moisture content in natural fiber increased. This led to a loss in dimensional stability and degradation. This causes weak adhesion between the polymer matrix and the natural fiber when the natural fibers used as reinforcement in composites17. Surface adhesion is a key factor in describing component mechanical and physical characteristics80,81. These problems can be solved by surface modification treatment such as chemical, physical and biological treatments17. Chemical treatment. Since natural fibers are hydrophilic and polymer matrix is hydrophobic, there is an inherent incompatibility between them, this results at the interface in weak bonding.  Chemical treatment methods will reduce the fiber’s hydrophilic nature by removing hydrophilic OH groups from reinforcing fiber81. This treatment strengthens the adhesion of the polymer matrix to the fiber via chemical reactions53,60. Alkaline treatment or mercerization: This method of treatment is the simplest, most cost-effective, and efficient for improving the adhesive capabilities between polymer matrix and natural fibers53. In this chemical treatment, aqueous sodium hydroxide (NaOH) is used. Natural fibers are soaked in a predetermined concentration of NaOH for a certain time and temperature. Non-cellulosic components like lignin, hemicellulose, oils, and wax are removed during this process60. The following reaction shows alkali treatment in below equation80. Fiber OH þ NaOH ! Fiber O Naþ þ H2O (1) The removal of non-cellulosic components modifies the polymerization degree and structural orientation of cellulose crystallites, altering the chemical composition of the fibers. Also, this treatment has a permanent effect on mechanical fibers behavior, particularly on their stiffness and strength. Various alkaline treatment studies indicated that mercerization would increase the amorphous cellulose amount at the crystalline cellulose expense and remove hydrogen bonds in the network structure80. Neutralizing the fibers can be achieved by using acetic acid to end the reaction by removing the rest of the hydroxyl groups after washing the fibers with distilled water82. Silane treatment: Saline is a molecule of multifunctional. It is used as a binding agent to adjust the surface of fibers. Saline coupling agent develops a siloxane bridge chemical bond between the polymer matrix and the fiber. Silanols form when moisture and a hydrolysable alkoxy group are present. One silanol end reacts with the matrix functional group during condensation, whereas the other end reacts with the cellulose hydroxyl group81. The following reactions show silane treatment in below equations83.

Applications Of Biodegradable Polymer

The use of biodegradable polymers is rapidly growing with a global industry worth many billions of dollars annually. Biodegradable polymers are used in a variety of applications, including food packaging, computer keyboards, automotive interior parts, and medical applications like implantable large devices, medical delivery and tissue engineering101–104. Figure 7 shows various applications of biopolymer materials101.

Environmental Fate and Assessment

Biodegradable polymers have been designed and developed over the past 20 years. They are used in applications that advantage biodegradation. Biodegradation is a biological process in which bacteria digest dead organic matter and convert it to microbial energy and biological mass while releasing inorganic compounds as by-products. Biodegradation is used in waste management to convert biowaste into compost for soil fertilization through organic recycling. Anaerobic digesters are another type of organic recycling system that produces biogas and digestate, which is subsequently transformed into compost. Biopolymers are developed to be reused in composting facilities and anaerobic digesters with bio-wastes. Biopolymers are also utilized in agricultural plastics that are made to be left in the field and biodegrade after usage. The environmental effect of compounds produced during polymer biodegradation and composting, which might then be dispersed into the environment by compost fertilization or directly diffused during their biodegradation in soil, is a recurring subject. End-of-life possibilities for biodegradable polymers are represented in Fig. 8.

Biodegradation end products

Chemical elements can be found in nature as components of organic molecules (such as polysaccharides, and so on) as well as in inorganic substances (such as NH3, CO2, and so on). Microorganisms transform lifeless organic materials into inorganic chemicals during biodegradation. Glucose molecules, for example, are converted back into the inorganic compounds that plants used to create glucose via aerobic biodegradation. This process is termed as mineralization as it leads in the transformation of organic material molecules into inorganic compounds and minerals. Organic molecules, like natural polymers and certain man-made polymers, are affected by the biodegradation process. Biopolymers are used in the manufacture of plastic materials that are designed to decompose in the soil or compost plants. Biodegradation of a polymeric compounds in which part of the original carbon (Cpolymer) is mineralized (CO2), part is consumed by microorganisms for their own development and reproduction (Cbiomass), and the rest remains as polymeric residue (Cresidue). Other kinds of microorganisms are engaged in the biodegradation process under anaerobic circumstances. As a result, products such as CO2 and CH4 are produced.

Biodegradation during organic recycling Organic recycling is a treatment process of bio-waste that results in the generation of compost (stabilized organic matter) that is utilized as a soil fertilizer in agriculture. Organic recycling is standardized and industrial biotechnology that involves a multistep biodegradation process in anaerobic digesters or aerobic composting plants. Organic recycling involves three strategies namely; industrial composting, home composting, and anaerobic digestion. Industrial composting. This technique can be used to handle bio-waste obtained by home, industrial, and agricultural processes. In addition, bio-waste from sewage treatment, park and garden upkeep are used. Composting refers to organic matter recycling method that turns waste into compost. Biodegradable plastic materials that have been used before are an ideal feedstock for industrial composting. Bio-waste is collected in industrial composting plants, where a variety of elements come together to provide a perfect environment for microorganisms to improve the composting process: temperature, moisture, and pH change over time. During the process, O2 should be available. Microorganisms get energy and chemical ingredients for their own survival, development, and reproduction through this mechanism. Microbial metabolism generates heat, which leads to increase pile temperature. As the temperature of the mass increases, quicker reactions take place, speeding up the biodegradation process. Home composting. When compared to industrial composting, home composting is applied to a lower amount of bio-waste created through domestic activities or garden upkeep and is done in a much more varied manner. As a result, home composting can provide different results due to the fact that numerous elements influence the process such as moisture, temperature and types of microorganisms. Because the compact dimensions of the composting masses may not be allowed for high temperatures to be attained, home composting is frequently slower than industrial composting. Anaerobic digestion. Bio-waste is decomposed by a bacterial population in the absence of oxygen, resulting in the formation of biogas (methane and carbon dioxide) and digestate, with little or no exothermic heat released. A two-step method is used by most commercial anaerobic digestion systems. Anaerobic fermentation is the initial process, followed by aerobic composting in the second step.

Biodegradationin soil Several

Biopolymer-based applications that end up in the soil after use are fast growing in the market. Furthermore, it is used to improve soil quality, mature industrial compost, which is made from a feedstock containing biopolymers, ends up in the soil. Soil is a heterogeneous material governed by a mix of environmental and seasonal elements that tightly control the microbial population’s creation and activity. For example, bacteria colonize an alkaline-neutral humid soil, however fungi require acid dry soil to thrive and operate.

Recycling Of Plastics And Biopolymer

All possible recycling techniques should be investigated to optimize the environmental advantages of these materials105. There are four different recycling paths as shown in Fig. 9. They are involved after collection, separation, and purification of plastic garbage106. They are primary recycling, secondary recycling (mechanical recycling), tertiary recycling (feedstock or chemical recycling), and quaternary recycling (energy recovery)107. Because of its simplicity and low cost, primary recycling is the most used method107. Primary recycling is mechanical recycling which is a closed-loop recycling technology that can only be used on high-quality plastic trash with a known history105. This method entails reusing things in their original form. The disadvantage of this method is that there is a certain limit on the number of cycles for each material107. Primary recycling allows the recycled material to be utilized in applications that have the same properties and performance as virgin plastics. It is usually not linked to postconsumer plastics rather to the conversion of uncontaminated plastic waste (e.g., production leftovers) into its original pellet or resin form within the same manufacturing facility. Hence, it does not need sorting and cleaning. Secondary recycling is the mechanical reprocessing of waste and plastics after consumption. Materials recycled through secondary recycling have lower mechanical properties compared to the mechanical properties of the original product. The lower mechanical propertied of secondary materials recycled are attributed to lower material purity and deterioration processes that result during the life of the product. Secondary recycling may be economically inexpensive if the amount of waste is small or/ and contaminated. Otherwise, the cost of recycling increases due to the separation and purification steps. Although mechanical recycling is a well-established recycling approach for conventional plastics, it should be used with caution when it comes to biodegradable plastics105. This is due to the sensitivity of biodegradable materials to heat108.

Natural Fiber Reinforced Composites

Natural fiber polymer composite (NFPC) is a composite substance comprising of a matrix of polymer reinforced with natural fibers with good strength properties113. The natural polymer reinforced composite has taken great interest in many applications. This is because natural fibers offer more and good benefits and qualities than synthetic fibers. Natural fibers have low weight, low cost, renewable and available materials. They are considered less harmful to processing equipment. It also has relatively good mechanical properties like flexural modulus and tensile modulus, as well as an enhanced surface finish of the molded parts composite114, stability during manufacturing, biological degradation, and limited health risks. Natural fiber polymer composites with excellent mechanical strength and stiffness may be made by integrating a light-weight and durable natural fiber into a polymer matrix (thermoset and thermoplastic)115. They are used in many applications which are rapidly increased in various engineering fields. The different types of NFPCs have got great attention in various automotive applications. Also, the other natural fiber composites are found in various applications like building and construction industry, window frame, panels, sports, aerospace, and bicycle frame116.

Characterization Of Natural Fibers, Biodegradable Polymers and Biocomposites

Mechanical properties

Natural fibers have good mechanical strength, modulus of elasticity and they are tough. The composites from natural fibers are served for commercial purpose and become a good substitute of synthetic fibers in various applications117. When comparing natural fibers with glass fibers, the most important features of natural fibers are inexpensive, good mechanical properties due to lower density of them, easy processing and handling, renewable resources, recyclable, and has good acoustic and thermal insulation ability118. Kim et al.119 reported that natural fiber-reinforced composites with high-strain rates absorb more energy than glass-fiber-reinforced composites. Natural fibers have drawbacks such as low strength, variation in quality, high absorption of moisture, treatment temperatures are limited, low durability and less resistance to combustion117,118. In general

Environmental stress cracking (ESC)

Among the most common prevalent causes of abrupt brittle breaking of thermoplastic polymers is environmental stress cracking (ESC). The chemical composition of the polymer, bonding, crystallinity, surface roughness, molar mass, and residual stress are all variables that impact the rate of ESC. There is no long-term chemical alteration, although the symptoms are similar to those of SCC. Srisa et al.174 studied antifungal bioplastic films, developed based on PLA and poly(butylene adipateco- terephthalate) (PBAT) blends with incorporated trans-cinnamaldehyde. Mold was discovered on bread that were preserved in ordinary PP films. According to PP’s forensic engineering, additional storage resulted in the development of fungal growth over the entire loaf on day 4 as shown in Fig. 18, 1 a. Mold mycelium expansion was successfully reduced by PLA/PBAT films and microbiological growth was not detected in any of the films containing trans-cinnamaldehyde (Fig. 18a). This is because the bacteria were successfully suppressed by large levels of trans-cinnamaldehyde release. Juraj Svatík et al.175 studied the mechanical strength and toughness of neat PLA and PLA bamboo biocomposites. It was found that the solid specimen and uniform porosity specimens were brittle and was broken up catastrophically. However, the gradient porosity specimens were quasi-ductile with no catastrophic breakdown and much greater strain at break as shown in Fig. 18b.

CONCLUSION

Egg shell, Banana peel, Fish Scale etc. should not be disposed in environment which pollute the earth. Biodegradable polymers obtained from them can be used alone or blended with each other to exhibit various excipients properties like Fillers, Disintegrants, Binders, Wetting agents etc. The proper research in this area can gives ecofriendly and recycling based society which ultimately give zero discharge and sustainability. biodegradable polymers, and polymers from renewable agricultural waste sources such as grape and tomato pomace, green tea extracts, essential oils, and curcumin, coconut shells, vegetable waste, rice husks, fruit peels, grapefruit seed extract, waste vegetables, maize and wheat starch, and municipal agro wastes. Sustainability is a primary criterion that influences the choice of the precursor (the type of agro-wastes). The production of biopolymers requires commercially viable quantities of agro-waste—a key challenge considering that the wastes occur at the retail and household levels, and there is no mechanism for sorting and disposal of the wastes. Additionally, there is a global variability in the availability of agro-wastes, a factor that influenced the mechanical and optical properties of the polymers developed. Fruit peels and coconut shells are common in fruit growing regions in tropical and subtropical areas, and coastal areas, respectively. Grape pomace waste is available in regions with grapevines such as Italy. The variations in the availability of waste impact the rate of production. Another constraint is the lack of facile and scalable synthetic routes. New and novel methods are based on laboratory models or experiments, which have not been applied on a commercial scale. Commercial methods include copolymer blending and chemical synthesis; these methods led to the formation of biofilms and bio-plastics, which are not 100% biodegradable. The reinforcement of the mechanical properties involves a trade-off with the elongation at break, thermal degradation ability (at the end of life treatment), and ecological impact, including carbon footprint, and eco-toxicity.

ACKNOWLEDGEMENT: -

Authors are thankful to the “first and foremost, I would like to praise and thank God, the Almighty, who has granted countless blessings, knowledge, and opportunity to the writer. The Authors are thankful to the Management & Principal of Satyajeet College Of Pharmacy, Mehkar for Providing facilities to carry out the work. The authors are thankful to Project Guide Prof. Vinod S Chaware. The authors are also thankful to Prof. Tejas J. Sharma Providing the ideas about the publication.

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