Environmental pollutions are increasing day by day due to more plastic application. The plastic material is going in our food chain as well as the environment employing microplastic and other plastic-based contaminants. From this point, bio-based plastic research is taking attention for a sustainable and greener environment with a lower footprint on the environment. This evaluation should be made considering the whole life cycle assessment of the proposed technologies to make a whole range of biomaterials. Bio-based and biodegradable bioplastics can have similar features as conventional plastics while providing extra returns because of their low carbon footprint as long as additional features in waste management, like composting. Interest in competitive biodegradable materials is growing to limit environmental pollution and waste management problems. Bioplastics are defined as plastics deriving from biological sources and formed from renewable feedstocks or by a variation of microbes, owing to the ability to reduce the environmental effect. The research and development in this field of bio-renewable resources can seriously lead to the adoption of a low-carbon economy in medical, packaging, structural and automotive engineering, just to mention a few. This review aims to give a clear insight into the research, application opportunities, sourcing and sustainability, and environmental footprint of bioplastics production and various applications. Bioplastics are manufactured from polysaccharides, mainly starch-based, proteins, and other alternative carbon sources, such as algae or even wastewater treatment byproducts. The most known bioplastic today is thermoplastic starch, mainly as a result of enzymatic bioreactions. In this work, the main applications of bioplastics are accounted. One of them being food applications, where bioplastics seem to meet the food industry concerns about many the packaging-related issues and appear to play an important part for the whole food industry sustainability, helping to maintain high-quality standards throughout the whole production and transport steps, translating into cleaner and smarter delivery chains and waste management. High perspectives resides in agricultural and medical applications, while the number of fields of applications grows constantly, for example, structural engineering and electrical applications. As an example, bio-composites, even from vegetable oil sources, have been developed as fibers with biodegradable features and are constantly under research.
Biodegradation of bioplastics depends on their physical and chemical structures in terms of polymer chains, functional groups and crystallinity, but also on the natural environment in which they are placed (i.e., moisture, oxygen, temperature and pH). Biodegradation is an enzymatic reaction catalysed in different ecosystems by microorganisms, such as actinobacteria (Amycolatopsis, Streptomyces), bacteria (Paenibacillus, Pseudomonas, Bacillus, Bulkholderia) and fungi (Aspergillus, Fusarium, Penicillium) (Emadian et al. 2017). There are different concepts of biodegradation. One very common degradation process is called hydrolysis. The hydrolysis mechanisms are exaggerated by diffusion of water through polymer matrix. Time duration for the degradation may vary for different material, such as polylactic acid, has very slow degradation which is about 11 months (Thakur et al. 2018). Moreover, the biodegradation rate be contingent on the end-of-life decisions and the physico-chemical conditions, such as moisture, oxygen, temperature, presence of a specific microorganism, presence of light. The main end-of-life choices for biodegradable plastics include recycling and reprocessing, incineration and other recovery options, biological waste treatments, such as composting, anaerobic digestion and landfill (Mugdal et al 2012; Song et al. 2009). The composting process represents the final disposition most favourable from an environmental point of view. The presence of ester, amide, or hydrolyzable carbonate increases biodegradation's susceptibility.
These non-biodegradable bioplastics are from renewable natural resources, that is from biomass without having the bio-degradation characteristics (Rahman and Bhoi 2021). This last is formed in a major part in Brazil, where they produce bioethanol from sugarcane by a fermentation route. The biopolyethylene is also produced from bioethanol, as other common bioplastics: polyethylene terephthalate (bio-PET), bio-PP or polypropylene (bio-PVC, polyvinyl chloride (bio-PVC),bio-PET, (Rujnić-Sokele and Pilipović 2017).
Instead, PHAs in Fig. 3 shown a general structure are a varied cluster of biopolymers, but typically denote to poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxy valerate) (PHBV). They are mostly produced from sugar or lipids by bacteria because PHAs represent an intracellular product of bacteria. Around 250 types of bacteria help to yield PHA. So, these bioplastics are collected with the demolition of bacteria and then disconnected from the microbial cell matter. Moreover, PHAs have good barrier characteristic and attractive in different biomedical applications. They also have the standard specification from marine degradability, which is ASTM D7081.
Agricultural applications of PHAs-based bioplastics are limited to nets, grow bags, and mulch films. Bioplastics-based nets are alternatives to high-density polyethylene, traditionally used to increase the crop's quality and yield and protect it from birds, insects, and winds. Grow bags, known also as planter bags or seedling bags, are commonly made of low-density polyethylene. Instead, PHAs-based grow bags would be biodegradable, root-friendly, and non-toxic to the surrounding water bodies. Finally, bioplastics in mulch films are essential to uphold exceptional soil structure, moisture retention, control weeds, and prevent contamination, in substitution of fossil-based plastics (El-malek et al. 2020).
Starch is usually obtained from different terrestrial crops. Distilled water, glycerol, and vinegar were used to modify cassava starch for the production of bioplastic sheets (Mojibayo et al. 2020). Bioplastics from cassava starch were re-inforced also by coconut husk fibers (Babalola and Olorunnisola 2019). Condensation polymerization was performed to produce bioplastic from corn starch and glycerin to obtain nanocomposites for packaging applications (Ateş and Kuz 2020). Other starch sources are potatoes, wheat, and tapioca. The finest, smoothest, flexible and strong bioplastic was produced from tapioca starch (Gökçe 2018), but the potato-derived starch showed the best properties in terms of extraction, ease of working, texture, and potential drying (Hamidon 2018). Composite bioplastics from tapioca starch and sugarcane bagasse fiber were recently investigated and ultrasounds treatment improved properties by enhancing the tensile strength and decreasing the moisture absorption rate (Asrofi et al. 2020).
Wastes from the food-processing industry are an important potential source of bioplastics (Tsang 2019; Jõgi and Bhat 2020). Vegetable wastes used to produce novel bioplastic films were carrots, radicchio, parsley, and cauliflowers (Perotto 2018). Novel starch- and/or cellulose-based bioplastics were produced from rice straw (Fig. 9), an agricultural waste usually used for bioethanol production (Agustin et al. 2014; Bilo 2018), and other agricultural wastes (Chaisu 2016).
A residual product of crude oil palm production is an empty fruit bunch, composed of cellulose, hemicellulose, and lignin. Having high cellulose content (36.67%), this abundant waste could be used to produce bioplastics (Isroi and Panji 2016; Isroi et al. 2017). Microcrystalline cellulose and glycerol were added to keratin from waste chicken feathers to produce biopolymeric films (Ramakrishnan et al. 2018; Sharma et al. 2018). Microcrystalline cellulose was a re-inforcing additive in bioplastic production also from avocado seeds (Sartika et al. 2018), jackfruit seeds (Lubis et al. 2018), and cassava peels (Maulida and Tarigan 2016). Waste cassava peels were investigated in combination with kaffir lime essential oil for future applications in industry and medicine (Masruri et al. 2019). Cocoa pod husk and sugarcane bagasse, which are wastes from the chocolate industry and the sugar industry, respectively, are promising for the production of biodegradable plastic films (Azmin et al. 2020). Bioplastics could be produced by injection molding from rapeseed oil production by-products, such as press cake or meal (Delgado et al. 2018). New bioplastics were prepared from potato peels and waste potato starch with eggshells and/or chitosan (from exoskeleton seafood wastes) as additives (Kasmuri and Zait 2018; Bezirhan Arikan and Bilgen 2019). Also, banana peels were used to produce a bioplastic with the addition of corn starch, potato starch, sage, and glycerol (Sultan and Johari 2017; Azieyanti et al. 2020). Bloodmeal is a low-value protein-rich by-product from meat processing, that is convertible into a bioplastic material (Low et al. 2014). Bioplastic fibers were fabricated also from gum arabic by electrospinning method (Padil et al. 2019).
Microalgae are a promising alternative source for bioplastics production because of their fast growth and no competition with food (Rahman and Miller 2017). Recently, several works investigated the synthesis of bioplastics from microalgae (Beckstrom et al. 2020; Simonic and Zemljic 2020). Microalgae could be used directly as biomass to produce bioplastics or indirectly by the extraction of PHBs and starch within microalgae cells. Other approaches include the production of microalgae-polymer blends through compression/hot molding, melt mixing, solvent casting, injection molding, or twin-screw extrusion (Cinar et al. 2020).
The most investigated microalgae were Chlorella and Spirulina. Chlorella seems to have better bioplastic behavior, whereas Spirulina showed better blend performance (Zeller et al. 2013). Different species of Chlorella were used in biomass-polymer blends containing polymers and additives (Cinar et al. 2020). Moreover, bioplastic may be produced from Chlorella pyrenoidosa (Das et al. 2018) and Chlorella sorokiniana-derived starch granules (Gifuni et al. 2017). Similar to Chlorella, Spirulina was investigated for bioplastic production (Cinar et al. 2020). For example, a bioplastic-based film was produced from salt-rich Spirulina sp. residues with the addition of polyvinyl alcohol (Zhang et al. 2020). Another bioplastic was prepared from Spirulina platensis, showing good biodegradability (Maheshwari and Ahilandeswari 2011). Other microalgae or cyanobacteria used to produce bioplastics were Chlorogloea fritschii (Monshupanee et al. 2016), Calothrix scytonemicola (Johnsson and Steuer 2018), Neochloris oleoabundans (Johnsson and Steuer 2018), residual Nannochloropsis after oil extraction (Yan 2016), Nannocloropsis gaditana (Torres et al. 2015; Fabra et al. 2017), Phaeodactylum tricornutum (Hempel 2011), and Scenedesmus almeriensis (Johnsson and Steuer 2018). Ten green microalgae were screened for starch production and starch-based bioplastic development. C. reinhardtii 11-32A resulted in the most promising starch-producing strain with interesting plasticization properties with glycerol at 120 °C (Mathiot et al. 2019). 2b1af7f3a8