BIOPLASTICS Bioplastics are a form of plastics derived from renewable biomass sources, such as vegetable fats and oils, corn starch, pea starch or microbiota. There are a variety of materials bioplastics that can be composed of, including: starches, cellulose, or other biopolymers. APPLICATIONS OF BIOPLASTICS Biodegradable bioplastics are used for disposable items, such as packaging and catering items (crockery, cutlery, pots, bowls and straws). They are also often used for bags, trays, containers for fruit, vegetables, eggs and meat, bottles for soft drinks and dairy products, and blister foils for fruit and vegetables.
Nondisposable applications include mobile phone casings, carpet fibres, and car interiors, fuel line and plastic pipe applications, and new electro active bioplastics are being developed that can be used to carry electrical current. In these areas, the goal is not biodegradability, but to create items from sustainable resources. Medical implants made of PLA, which dissolve in the body, save patients a second operation. Compostable mulch films for agriculture, already often produced from starch polymers, do not have to be collected after use and can be left on the fields.
TYPES OF BIOPLASTICS Starch-based plastics: Constituting about 50 percent of the bioplastics market, thermoplastic starch, currently represents the most widely used bioplastic. Pure starch possesses the characteristic of being able to absorb humidity, and is thus being used for the production of drug capsules in the pharmaceutical sector. Flexibiliser and plasticiser such as sorbitol and glycerine are added so the starch can also be processed thermo-plastically.
By varying the amounts of these additives, the characteristic of the material can be tailored to specific needs. Simple starch plastic can be made at home. Industrially, starch based bioplastics are often blended with biodegradable polyesters. These blends are no longer biodegradables, but display a lower carbon footprint compared to the corresponding petroleum based plastics. Cellulose-based plastics: Cellulose bioplastics are mainly the cellulose esters, (including cellulose acetate and nitrocellulose) and their derivatives, including celluloid.
Polylactic acid (PLA) plastics: Polylactic acid (PLA) is a transparent plastic produced from cane sugar or glucose. It not only resembles conventional petrochemical mass plastics (like PE or PP) in its characteristics, but it can also be processed easily, albeit more expensively, on standard equipment that already exists for the production of conventional plastics. PLA and PLA blends generally come in the form of granulates with various properties, and are used in the plastic processing industry for the production of foil, moulds, cups and bottles.
Poly-3-hydroxybutyrate (PHB): The biopolymer poly-3-hydroxybutyrate (PHB) is polyester produced by certain bacteria processing glucose, corn starch or wastewater. Its characteristics are similar to those of the petroplastic polypropylene. PHB is distinguished primarily by its physical characteristics. It produces transparent film at a melting point higher than 130 degrees Celsius, and is biodegradable without residue. Polyhydroxyalkanoates (PHA): Polyhydroxyalkanoates are linear polyesters produced in nature by bacterial fermentation of sugar or lipids.
They are produced by the bacteria to store carbon and energy. In industrial production, the polyester is extracted and purified from the bacteria by optimizing the conditions for the fermentation of sugar. More than 150 different monomers can be combined within this family to give materials with extremely different properties. PHA is more ductile and less elastic than other plastics, and it is also biodegradable. These plastics are being widely used in the medical industry. Polyamide 11 (PA 11): PA 11 is a biopolymer derived from natural oil.
PA 11 belongs to the technical polymers family and is not biodegradable. The emissions of greenhouse gases and consumption of nonrenewable resources are reduced during its production. Its thermal resistance is also superior to that of PA 12. It is used in high-performance applications like automotive fuel lines, pneumatic airbrake tubing, electrical cable antitermite sheathing, flexible oil and gas pipes, control fluid umbilicals, sports shoes, electronic device components, and catheters. IMPACT ON ENVIRONMENT Sustainability:
Sustainability is improving the quality of human life while living within the carrying capacity of supporting eco-systems. The production and use of bioplastics is generally regarded as a more sustainable activity when compared with plastic production from petroleum (petroplastic), because it relies less on fossil fuel as a carbon source and also introduces fewer, net-new greenhouse emissions if it biodegrades. They significantly reduce hazardous waste caused by oil-derived plastics, which remain solid for hundreds of years, and open a new era in packing technology and industry. Biodegradable:
All (bio- and petroleum-based) plastics are technically biodegradable, meaning they can be degraded by microbes under suitable conditions. However many degrade at such slow rates as to be considered non-biodegradable. Some petrochemical-based plastics are considered biodegradable, and may be used as an additive to improve the performance of many commercial bioplastics. The degree of biodegradation varies with temperature, polymer stability, and available oxygen content. Consequently, most bioplastics will only degrade in the tightly controlled conditions of industrial composting units.
In compost piles or simply in the soil/water, most bioplastics will not degrade, starch-based bioplastics will, however. A distinction must be made for the term “compostable”. While “biodegradable” simply means that an object will biologically disintegrate, compostable specifically demands that the end product has to be humus. So, while a plastic may “biodegrade in a compost site” this does not mean that it will compost in a compost site. ADVANTAGES Bioplastics can be sustainable, carbon neutral and are always renewable, because they are made from plant materials which can be grown indefinitely.
These plant materials come from agricultural nonfood crops. Therefore, the use of biopolymers would create a sustainable industry. In contrast, the feedstocks for polymers derived from petrochemicals will eventually deplete. In addition, biopolymers have the potential to cut carbon emissions and reduce carbon dioxide (CO2) quantities in the atmosphere: this is because the CO2 released when they degrade can be reabsorbed by crops grown to replace them: this makes them close to carbon neutral.
Some biopolymers are biodegradable: they are broken down into CO2 and water by microorganisms. Some of these biodegradable biopolymers are compostable: they can be put into an industrial composting process and will break down by 90% within six months. DISADVANTAGES Bioplastics could have a damaging effect on soil, water usage and quality, and result in higher food prices. Bioplastics are designed to be composted, not recycled. The plant-based material will actually contaminate the recycling process if not separated from conventional plastics such as soda bottles and milk jugs.
Home composting may not be an option. Some bioplastics cannot be broken down by the bacteria in our backyards. Polyethylene (PE) made from cane sugar is one example of this. Only bioplastics that are fully biodegradable will break down in a home compost pile, and it could still take up to two years for certain items. The rest require the high heat and humidity of an industrial composting facility. Plants grown for bioplastics have negative impacts of their own.
Bioplastics are often produced from genetically modified food crops such as corn, potatoes, and soybeans, a practice that carries a high risk of contaminating our food supply. Also, corn and soybean producers typically apply large amounts of chemical pesticides and fertilizers that pollute our air and water. To compound matters, the growth of the bioplastics and biofuels industries (both of which currently rely on food crops as their raw material) increases the demand for crops, puts pressure on food prices, and increases the impact of agriculture worldwide.