Analysts have been predicting significant growth in the market for greener ‘bioplastic’ food packaging materials for some years now, but despite some strong interest from food manufacturers, retailers and consumers, those predictions have proved overly optimistic. New biodegradable plastics like PLA, made from renewable materials and with a much smaller environmental footprint than conventional oil-based plastics, have made inroads into the food packaging market, but have yet to really take off. Concerns over the cost and performance of bioplastics have been hard to overcome and have blunted moves to establish them as viable alternatives to traditional plastics. But the main drivers of interest in bioplastics, growing awareness of environmental issues and the rising cost of oil, have not gone away. Once again, great things are being forecast for bioplastics, but this time predictions are being made in the light of some important technological developments and major investments by the chemical and packaging industries. Are bioplastics finally about to have their day, and can they really prove their green credentials?

In December 2010, UK-based packaging research and consultancy organisation Pira International published a market research report entitled The Future of Bioplastics for Packaging to 2020. The report defines bioplastics as "materials that are either biodegradable and compostable and derived from both renewable and non-renewable sources, or materials that are non-biodegradable and derived from renewable resources. Trade body European Bioplastics puts it rather more succinctly as "Bioplastics are biobased, biodegradable, or both."

What is clear from definitions like these is that the term can be applied to a very wide range of different polymers. That in itself could be a problem if the range of materials qualifying as bioplastics becomes so broad that it ceases to have any real meaning to consumers, diluting the environmental message. The same is true to some extent for the terms ‘biodegradable’ and ‘compostable’, neither of which always means quite what one might imagine. In fact the European Commission is already running a public consultation on the issue in advance of drawing up clear legislative definitions of biodegradable and compostable. The object of the exercise is to ensure that consumers are not misled by green claims attached to plastics.

Nevertheless, the currently accepted definition of bioplastics is something along the lines of the Pira version above and it covers some interesting and potentially important developments. Pira’s report forecasts rapid growth in the market for bioplastics, with a CAGR (compound annual growth rate) of nearly 25% from 2010-15 slowing to 18.3% by 2020. The total global demand for bioplastic packaging is predicted to be 884,000 tonnes by 2020. To put that in perspective, an earlier Pira report estimated that in 2006, global production of biodegradable packaging – the term bioplastic was not so widely used at the time – was a relatively insignificant 42,000 tonnes. Food packaging is expected to be one of the largest sectors helping to drive this growth. While Europe is currently the biggest market for bioplastic packaging, thanks to "favourable consumer and retail attitudes to sustainable packaging" and government support for developing recycling and composting infrastructure, North America and Asia are expected to show faster growth to 2020. Equally bullish predictions have been made before, but this time there are technological developments in the pipeline that can explain how such dramatic growth can be achieved.

The current bioplastics scene

The leading bioplastic for food packaging remains polylactide (PLA). PLA was first discovered more than a hundred years ago, but remained far too expensive for packaging applications until the late 1980’s, when scientists working for Cargill in the USA developed a more efficient production method. The raw material for PLA can be any biomass that is high in starch or sugars, including maize, sugar cane, sugar beet and potatoes. The starch is first converted into fermentable dextrose, which is then used as the food source for a microbial fermentation that produces lactic acid. The lactic acid is then polymerised by means of some clever chemistry. The process can be controlled and modified to produce different types of PLA suitable for various applications.

The biggest commercial producer of PLA is NatureWorks LLC in the USA, a subsidiary of Cargill set up in 2001 to utilise the technology developed by the parent company. NatureWorks has a dedicated factory in Nebraska able to make up to 140,000 tonnes of its Ingeo™ branded PLA products every year from locally grown maize. PLA can be used in a variety of applications and can be formulated to be rigid or flexible. It can be thermoformed, blow moulded, injection moulded and used to make films, coatings and flow wraps. It can also be heat sealed at relatively low temperatures and is claimed to have barrier properties similar to those of PET. Its main limitations are poor resistance to high temperatures, and a lack of strength and translucence compared with some other plastics. Some food manufacturers have also expressed concerns over the barrier properties of PLA, but the main disadvantage remains cost, which is said to be roughly 20% higher than conventional plastics.

Cost is probably the main reason why manufacturers and retailers have not made more use of PLA. Despite serious evaluations and some commercial trials with PLA packaging, comparatively few food products are packed in the material at present. In fact, some manufacturers have abandoned their use of PLA and returned to conventional plastic packaging. But this is not to say that PLA has been unsuccessful. The Pira report shows that it accounted for a 42.5% share of the entire global bioplastic packaging market in 2010 and it is widely used for foodservice trays and containers. Recently, French food giant Danone announced that it would be using PLA cups for the Activia range of drinking yoghurts in Germany. Nevertheless, Pira predicts a decline in market share over the next ten years.

Whether or not PLA loses market share in the coming years, some PLA-based packaging materials are still attracting a lot of interest. There have been a number of attempts to improve the functionality of PLA using additives, including nanoparticles and copolymers, and chemical modifications designed to give better strength, heat resistance and barrier properties. But it is PLA-based flexible films that seem to hold the most promise for future growth and development. In particular, bi-axially oriented PLA (BOPLA) films are seen to have great potential. The Pira report identifies BOPLA films as one of developments that will drive demand for bioplastic packaging as they become more widely available and their performance improves. BOPLA products are already commercially available, with an example being the NATIVIA™ range launched in 2010 by Dubai-based supplier Taghleef Industries. The NATIVIA product range includes metallised and transparent films designed for different food packaging applications, including fresh produce, bakery products, snacks and confectionery. BOPLA films lend themselves to modification, especially by the addition of mineral nanoparticles, so that their barrier characteristics can be improved. As new BOPLA based products come on the market, the number of practical applications is likely to increase and the costs come down.

There are other bioplastics already on the market too. Examples include starch-based biopolymers such as the Mater-Bi® range developed by Italian producer Novamont. These plastics are made from mixtures of corn-starch and thermoplastic binders, such as polyvinyl alcohol, polycaprolactone and PLA. They are biodegradable, though not all the components come from renewable sources, and are in use in a number of food packaging applications. Other starch-based bioplastics are also commercially available now, often blended with polymers and additives to produce a material with desirable characteristics. Film specialist Innovia has developed its NatureFlex™ films derived, not from starch, but from renewable wood pulp, and which have been successfully used for packaging fresh produce and other food products.

Polyhydroxyalkanoates set for growth

A rather different group of bioplastics currently receiving a lot of attention are the polyhydroxyalkanoates (PHAs), polymers produced naturally within some microbial cells. One of the best known is poly-3-hydroxybutyrate (PHB), produced by a range of bacterial species, such as Bacillus megaterium, but there are many other polymers in the group, including poly 3-hydroxyvalerate (PHV). PHAs are of great interest as bioplastics, mainly because their physical properties closely resemble those of polypropylene, but also because they are readily biodegradable. They are much more heat-resistant than PLA and are also hydrophobic, as well as water and oil-resistant.

The first commercial PHA product was a PHB-PHV copolymer called Biopol®, developed by ICI. In 2001, the Biopol name was acquired by US bioscience business Metabolix, which went on to develop the Mirel range of PHA-based bioplastics for food packaging and other applications. In 2006, Metabolix set up a joint venture with grain processor ADM called Telles, to produce and market Mirel products. The polymers are made by an industrial fermentation of maize sugar and applications include injection moulding, thermoforming, packaging films and paper coating. Although PHAs have many desirable properties and biodegrade in the environment, their main drawback as packaging materials is that they are quite brittle. However, mixing PHAs with other materials like clay nanoparticles in composites may be able to overcome this problem. The other problem with PHAs is cost; currently around double that of equivalent petroleum-based plastics.

Nevertheless, the Pira report predicts a 41% CAGR for PHAs until 2020. One of the reasons for this optimism is the research work on PHA production currently being undertaken by Metabolix. Using its biotechnology experience, the company is investigating genetic modification of bacteria to make the production process more efficient, but it is also looking at modifying plants to produce PHA and other materials directly within the plant itself. This could mean that PHAs might one day be extracted and refined from crops grown in the field without the costly microbial fermentation stage. That would have the effect of making PHAs much more competitive with other bioplastics and with conventional plastics.

Conventional plastics from renewable sources

Exciting as these developments may be, the really significant change in the bioplastics market may at first sight be something of a step backwards. One obvious way to overcome the functional limitations of existing bioplastics for food packaging is to go back to using tried and trusted conventional plastics, but with one crucial difference. If established polymer materials like PET and polypropylene can be made from renewable raw materials they become classified as bioplastics and throw off the petroleum-derived tag, thus making them a much more sustainable alternative, but with the advantage of having known performance characteristics. Some of the world’s biggest chemical companies are now investing in such technology.

Much of the activity centres on Brazil, where there is an established industry producing bio-ethanol from sugar cane. Currently, most of that bio-ethanol is used as an alternative fuel for motor vehicles, but it can also be used as a feedstock for producing polymers, including PE and PP. For example, Dow Chemical has recently announced a joint venture with Mitsui to build a bioplastics plant at Santa Vitoria to take advantage of the huge potential for sugar cane cultivation in the area. In 2010, Brazil’s own chemical giant Braskem SA opened its own plant designed to produce PP from sugar cane by a process developed in collaboration with Danish biotech business Novozymes. Bio-derived PE and other conventional plastics currently make up less than 1% of the global bioplastic packaging market, but Pira predicts a CAGR of 83% between now and 2020, which would increase that market share considerably. It is easy to see that plastics manufacturers stand to benefit from these developments in two ways. Firstly they free themselves from dependence on the increasingly volatile oil market, and secondly they become major players in the environment-friendly bioplastics sector, without the need to develop entirely new products.

There are other technological developments that could have a part to play in the future growth of the bioplastics market. Some of these involve exploitation of other naturally occurring polymers, such as chitin and xylan derived from renewable non-food sources, and are close to market. For example, US producer Cereplast has been developing bioplastic resins derived from algae. But one of the most exciting developments, singled out by the Pira report as having huge potential, is the production of bioplastics from carbon dioxide. Clearly the environmental benefits of converting atmospheric CO₂ directly into packaging material would be enormous if it can be made economically viable. One of several companies investigating this technology is US-based Novomer, set up in 2004 to commercialise research on catalysts carried out at Cornell University and develop low-cost green plastics from renewable feedstocks, including CO₂. The process uses a new type of highly active zinc-based catalyst to copolymerise carbon dioxide and various epoxides derived from renewable sources, like citrus fruit waste. The result is a range of biodegradable polycarbonate materials with obvious applications in packaging – perhaps the ultimate in bioplastics.

How green are bioplastics

The possibility of producing plastic from CO₂ is exciting, but it also highlights some of the more controversial aspects of some other bioplastic products. For instance, the biodegradability of bioplastics was initially seen as a major advantage, but manufacturers are now more likely to draw attention to the renewable raw materials. The main reason for this is that most bioplastics, notably PLA, will not biodegrade in landfill or in the natural environment, but only under the controlled conditions present in industrial composting systems.

Unfortunately, the infrastructure to deal with bioplastic waste is at an early stage of development. There are not enough waste composting systems, and sorting biodegradable plastic from other plastics for recycling is also difficult at present. This means that some PLA and other bioplastics will inevitably end up in landfill, where it will remain. The exception is PHA, which will biodegrade in the environment. But there have been suggestions that under certain conditions, the breakdown of PHA could release methane, a powerful greenhouse gas. These concerns have tarnished the green image of bioplastics to some extent and have also helped bio-derived conventional plastics to come to the fore. They may not biodegrade, but they are made from renewables and can be recycled using existing infrastructure.

Finally there are questions over sustainability, especially in relation to the use of agricultural land to grow crops that will be used to make plastic packaging, rather than food. This is particularly likely to become an issue in Brazil if forest is felled to create space to grow more sugar cane. If the increase in human population puts pressure on the food supply, competition for agricultural land will become intense. Making plastics from petroleum may not be sustainable, but neither is taking over food-producing land for bioplastics production. The short-term answer may be a combination of more efficient recycling and the use of raw materials derived from agricultural waste and non-food crops grown on marginal land. But in the longer-term, some of the technological developments in the pipeline could mean that all the raw material needed for plastic production can be obtained from the atmosphere in the form of carbon dioxide, thus neatly reversing a process that has been in progress for 100 years or more.

For further information

Pira International Market Intelligence Report - The Future of Bioplastics for Packaging to 2020

http://www.pira-international.com/