Bioplastics or organic plastics are a form of plastics derived from renewable biomass sources, such as vegetable oil, corn starch, pea starch, or microbiota, rather than fossil-fuel plastics which are derived from petroleum. Some, but not all, bioplastics are designed to biodegrade.
Biodegradable bioplastics are used for disposable items, such as packaging and catering items (crockery, cutlery, pots, bowls, straws). Biodegradable bioplastics are also often used for organic waste bags, where they can be composted together with the food or green waste. Some trays and containers for fruit, vegetables, eggs and meat, bottles for soft drinks and dairy products and blister foils for fruit and vegetables are manufactured from bioplastics.
Nondisposable applications include mobile phone casings, carpet fibres, and car interiors, fuel line and plastic pipe applications, and new electroactive 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.
Many bioplastics lack the performance and ease of processing of traditional materials. Polylactic acid plastic is being used by a handful of small companies for water bottles, but shelf life is limited because the plastic is permeable to water – the bottles lose their contents and slowly deform. Bioplastics are seeing some use in Europe though, where they account for 60% of the biodegradable materials market. The most common end use market is for packaging materials. Japan has also been a pioneer in bioplastics, incorporating them into electronics and automobiles.
Constituting about 50 percent of the bioplastics market, thermoplastic starch, such as Plastarch Material, currently represents the most important and 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 (also called “thermo-plastical starch”). Simple starch plastic can be made at home shown by this method.
The aliphatic biopolyesters are mainly polyhydroxyalkanoates (PHAs) like the poly-3-hydroxybutyrate (PHB), polyhydroxyvalerate (PHV) and polyhydroxyhexanoate PHH.
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 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, tins, cups, bottles and other packages
The biopolymer poly-3-hydroxybutyrate (PHB) is a polyester produced by certain bacteria processing glucose or starch. Its characteristics are similar to those of the petroplastic polypropylene. The South American sugar industry, for example, has decided to expand PHB production to an industrial scale. 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.
Polyamide 11 (PA 11)
PA 11 is a biopolymer derived from natural oil. It is also known under the tradename Rilsan B, commercialized by Arkema. PA 11 belongs to the technical polymers family and is not biodegradable. Its properties are similar to those of PA 12, although 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.
The basic building block (monomer) of polyethylene is ethylene. This is just one small chemical step from ethanol, which can be produced by fermentation of agricultural feedstocks such as sugar cane or corn. Bio-derived polyethylene is chemically and physically identical to traditional polyethylene – it does not biodegrade but can be recycled. It can also considerably reduce greenhouse gas emissions. Brazilian chemicals group Braskem claims that using its route from sugar cane ethanol to produce one tonne of polyethylene captures (removes from the environment) 2.5 tonnes of carbon dioxide while the traditional petrochemical route results in emissions of close to 3.5 tonnes.
Braskem plans to introduce commercial quantities of its first bio-derived high density polyethylene, used in a packaging such as bottles and tubs, in 2010 and has developed a technology to produce bio-derived butene, required to make the linear low density polethylene types used in film production.
Genetically modified bioplastics
Genetic modification (GM) is also a challenge for the bioplastics industry. None of the currently available bioplastics – which can be considered first generation products – require the use of GM crops, although gm corn is the standard feedstock.
Looking further ahead, some of the second generation bioplastics manufacturing technologies under development employ the “plant factory” model, using genetically modified crops or genetically modified bacteria to optimise efficiency.
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 .
However, manufacturing of bioplastic materials is often still reliant upon petroleum as an energy and materials source. This comes in the form of energy required to power farm machinery and irrigate growing crops, to produce fertilisers and pesticides, to transport crops and crop products to processing plants, to process raw materials, and ultimately to produce the bioplastic, although renewable energy can be used to obtain petroleum independence.
Italian bioplastic manufacturer Novamont states in its own environmental audit that producing one kilogram of its starch-based product uses 500g of petroleum and consumes almost 80% of the energy required to produce a traditional polyethylene polymer. Environmental data from NatureWorks, the only commercial manufacturer of PLA (polylactic acid) bioplastic, says that making its plastic material delivers a fossil fuel saving of between 25 and 68 per cent compared with polyethylene, in part due to its purchasing of renewable energy certificates for its manufacturing plant.
A detailed study examining the process of manufacturing a number of common packaging items in several traditional plastics and polylactic acid carried out by Franklin Associates and published by the Athena Institute shows the bioplastic to be less environmentally damaging for some products, but more environmentally damaging for others. This study however does not consider the end-of-life of the products, thus ignores the possible methane emissions that can occur in landfill due to biodegradable plastics.
While production of most bioplastics results in reduced carbon dioxide emissions compared to traditional alternatives, there are some real concerns that the creation of a global bioeconomy could contribute to an accelerated rate of deforestationif not managed effectively. There are associated concerns over the impact on water supply and soil erosion.
Other studies showed that bioplastics represent a 42% reduction in carbon footprint.
On the other hand, bioplastic can be made from agricultural byproducts and also from used plastic bottles and other containers using microorganisms .
Bioplastics and biodegradation
The terminology used in the bioplastics sector is sometimes misleading. Most in the industry use the term bioplastic to mean a plastic produced from a biological source. One of the oldest plastics, cellulose film, is made from wood cellulose. 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. Non-biodegradable bioplastics are referred to as durable. 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 (e.g. PH), starch-based bioplastics will, however. An internationally agreed standard, EN13432, defines how quickly and to what extent a plastic must be degraded under commercial composting conditions for it to be called biodegradable. This is published by the International Organization for Standardization ISO and is recognised in many countries, including all of Europe, Japan and the US. However, it is designed only for the aggressive conditions of commercial composting units. There is no standard applicable to home composting conditions. Natureworks PLA ( Corn Based ) grade 2000D under prEN 13432 standards showed complete composing degradation 97.5% after 60 day as compared with standard Cellulose 77.8% and passes fully the Belgium Organic Waste Systems tests.
The term “biodegradable plastic” is often also used by producers of specially modified petrochemical-based plastics which appear to biodegrade. Traditional plastics such as polyethylene are degraded by ultra-violet (UV) light and oxygen. To prevent this process manufacturers add stabilising chemicals. However with the addition of a degradation initiator to the plastic, it is possible to achieve a controlled UV/oxidation disintegration process. This type of plastic may be referred to as degradable plastic or oxy-degradable plastic or photodegradable plastic because the process is not initiated by microbial action. While some degradable plastics manufacturers argue that degraded plastic residue will be attacked by microbes, these degradable materials do not meet the requirements of the EN13432 commercial composting standard.The bioplastics industry has widely criticised oxo-biodegradable plastics, which the industry association says do not meet its requirements.Oxo-biodegradable plastics – known as “oxos” – are conventional petroleum-based products with some additives that initiate degradation.ASTM standard used by oxo producers is just a guideline. It requires only 60% biodegradation, P-Life is an oxo plastic claiming biodegradability in soil at a temperature of 23 degrees Celsius reaches 66% after 545 days.Dr Baltus of the National Innovation Agency, said there was no proven evidence that bio-organisms are really able to consume and biodegrade oxo plastics.
There are also concerns that bioplastics will damage existing recycling projects. Packaging such as HDPE milk bottles and PET water and soft drinks bottles is easily identified and hence setting up a recycling infrastructure has been quite successful in many parts of the world. However, plastics like PET do not mix with PLA, yielding unusable recycled PET if consumers fail to distinguish the two in their sorting. The problem could be overcome by ensuring distinctive bottle types or by investing in suitable sorting technology. However, the first route is unreliable, and the second costly.
Because of the fragmentation in the market and still unsettled definitions it is difficult to estimate the total market size for bioplastics, but estimates put global consumption in 2006 at around 85,000 tonnes. In contrast, global consumption of all flexible packaging is estimated at around 12.3 million tonnes.
COPA (Committee of Agricultural Organisation in the European Union) and COGEGA (General Committee for the Agricultural Cooperation in the European Union) have made an assessment of the potential of bioplastics in different sectors of the European economy:
- Catering products: 450,000 tonnes per year
- Organic waste bags: 100,000 tonnes per year
- Biodegradable mulch foils: 130,000 tonnes per year
- Biodegradable foils for diapers 80,000 tonnes per year
- Diapers, 100% biodegradable: 240,000 tonnes per year
- Foil packaging: 400,000 tonnes per year
- Vegetable packaging: 400,000 tonnes per year
- Tyre components: 200,000 tonnes per year
Total 2,000,000 tonnes per year
In the years 2000 to 2008, worldwide consumption of biodegradable plastics based on starch, sugar, and cellulose – so far the three most important raw materials – has increased by 600 %. The European Bioplastics trade group predicted annual capacity would more than triple to 1.5 million tons by 2011. BCC Research forecasts the global market for biodegradable polymers to grow at a compound average growth rate of more than 17 percent through 2012. Even so, bioplastics will encompass a small niche of the overall plastic market, which is forecast to reach 500 billion pounds (220 million tonnes) globally by 2010.