Strategic moves on the home front

Just 10 years ago, biodegradable bin bags would commonly start to disintegrate while they were still on the kerbside. For many, the small range of materials available were stuck somewhere between being a joke and a curiosity.

To Bruno de Wilde, laboratory manager at Belgian test house Organic Waste Services (OWS), these inauspicious beginnings were hardly a surprise. After all, decades of growth and development in oil-based plastics had been largely based on the fact that they did not biodegrade. A 180° shift in development criteria was never going to be a smooth transition.

But today, OWS is a leading European specialist in this area, and is busier than ever testing the compostability of increasingly complex bioplastic films and rigid materials. So how has this change come about? And what exactly does 'compostable' mean when applied to food packaging?

Confusion still surrounds much of the terminology in this area, and some distinctions need to be made. For their part, manufacturers of so-called 'oxo-degradable' materials (sometimes termed 'oxo-biodegradable' or just 'degradable') have done little to dispel this confusion. Oxo-degradables are polyolefin plastics (commonly polyethylene or polypropylene) with additives such as heavy-metal compounds which trigger fragmentation of the material under the correct conditions.

Peter Ettridge, sustainable packaging development manager at Amcor Flexibles, points out that the distinction here is not absolutely clear-cut, since some micro-organism activity is associated with this process of degradation. But for many, the fact that the oil-derived base plastic persists in the environment as a dust makes the 'biodegradable' tag highly questionable.

Moreover, unlike the rather meaningless term 'recyclable' (which can be stretched to cover most materials), 'compostable' is closely defined, and in Europe is defined by the EN 13432 standard (see panel story). From a testing viewpoint, the most important criteria are biodegradation and disintegration. Importantly, says de Wilde at OWS, biodegradability is a prerequisite for 'compostable' status, but not sufficient in its own right.

He points to one further significant distinction: EN 13432 is based on industrial composting, while there is no internationally-recognised standard for home composting.

"The main difference here is the temperature profile," he explains. "The typical industrial composting temperature of 60°C generates a form of pasteurisation, killing off pathogens. The heat loss in home composting is much greater, resulting in temperatures typically of just 10°C above ambient."

Home composting or home 'landfill'?

This major difference helps to explain why some national governments do not encourage, or even recognise, home composting as a bona fide form of waste management. According to de Wilde, some go so far as to describe it as "home landfill"

In the UK, on the other hand, it figures prominently in the national waste strategy, in local government initiatives and in supermarket packaging specifications. Why? Partly because of the importance of gardening as a national pastime, he suggests, and partly because the collection and industrial composting infrastructure is still insignificant.

Wherever the word 'organic' occurs, brand owners and retailers are still likely to spot a 'compostable' opportunity. Earlier this year, Alcan Packaging and Jordans Cereals won a DuPont Packaging Award for bags used on Jordan's organic muesli and granola. This is a laminate combining Innovia Films' NE30 Natureflex cellulose-based film (30 microns) and Novamont's Mater-Bi (90 microns), derived from cornstarch. The idea is that the transparency, rigidity and heat-resistance of the NE30 outer layer complements the strength of the Mater-Bi.

That isn't to say that even this new generation of biopolymers matches the performance of traditional plastics. David Maxwell from Alcan in Dublin, which developed the film, says the laminate offers a good gas barrier. "But other films have a better water barrier by a factor of four," he says.

Ensuring that the new structure met Jordan's one-year shelf-life and protection needs was a major part of Alcan's challenge. But the project's overall gestation period of two years can be explained by the requirements of DIN-Certco, the organisation which certifies products as 'compostable' under EN13432.

As de Wilde at OWS explains, tests can take into account up to five different non-biodegradable components which each comprise less than 1% of total pack weight, and together do not constitute more than 5%. These can include inks, adhesives varnishes and coatings.

According to Maxwell, there was also a theoretical risk that these elements might inhibit overall decomposition down to a tough 2-micron limit, or that the heavy-metal concentration in the inks (particularly copper in cyan) might fall foul of certification.

DIN-Certco's partner in the UK is the Association for Organic Recycling (AFOR), formerly the Composting Association. Business service director Melvyn Chimes explains: "Alcan's application was delayed because it was changed towards the end of the process so that it would be Jordans which was certificated, not Alcan." Even so, he claims the entire DIN-Certco process for the material took around six months.

Similarly, Ettridge plays down the testing and approval delays. He estimates that the total development time for Amcor's new NaturePlus compostable film was no longer than 18 months, including the compostability testing. "Like any other audit or certification procedure, once you've been through the DIN-Certco process a few times, it's not too difficult," he says.

The film is now being used on bags for Sainsbury's Organic Wild Rocket. Described by Ettridge as "non-laminated, modified cellulose", it had to meet Sainsbury's consumer-end requirements of being home compostable. It also had to perform well with a wet product, run at standard speeds in a wet environment and offer optimum sealing properties.

Both Amcor and Innovia expect to see more applications of their cellulose-based structures in medium shelf-life dry goods, as well as fresh produce.

Issues with polylactite

Other materials such as polylactide (PLA) continue to win new business. Recent applications of NatureWorks Ingeo PLA in Europe include a bottle for Sant'Anna mineral water in Italy.

But in the UK, while retailers such as Marks & Spencer have continued to use PLA because of its renewable origins, others such as The Co-operative avoid it, partly because it is not home compostable, even in thinner grades, and partly because the raw material cannot be guaranteed genetically modified-free.

Over the past year or two, this increased reluctance on the part of some converters, brands and retailers to commit to using PLA can in part be explained by concerns over supply. NatureWorks admits it needed to "de-bottleneck", but adds that it is on target to hit "nameplate capacity" (140,000t/year) at its Blair, Nebraska, plant in the first quarter of 2009.

In Germany especially, capacity increases from producers of other biopolymers, including BASF's Ecoflex and Ecovio materials, suggest that mainland Europe is expecting greater uptake linked to strengthened organic waste infrastructure.

In the UK, estimates as to the prevalence of home composting vary from as little as 3% to around 10% of the population. This domestic route aside, disposal routes in the UK are still very limited. Nonetheless, Ettridge argues: "If you wait until adequate industrial composting and anaerobic digestion (AD) infrastructure is in place before creating compostable packaging, you'll be waiting around forever."

The current focus on food waste will undoubtedly help to accelerate change. As Ettridge explains, in the Netherlands, compostable food packaging can already be included in municipal food waste collections. And while only a handful of local authorities in England and Wales are trialling food waste collections, there will be plenty more watching very carefully.

Just as 'recycling' complements 'reduction' in conventional packaging materials, composting and AD will increasingly have a role alongside reductions in supply-chain and household food waste. Compostable films make it far easier to collect date-expired food in a dedicated waste stream, reduce landfill and harvest valuable resources from that waste.

In the meantime, what on-pack message should retailers be communicating to consumers?

AFOR technical manager Emily Nichols says: "In the short-term, wording such as 'check food waste collection service' may be feasible. We are currently collaborating with the Waste & Resources Action Programme (WRAP) and other organisations on consumer focus group research to look into what could work." FM

Compostability broken down

Under the EN 13432 standard, there are four aspects to assessing compostability. These can be defined as follows:

l Material characteristics: In practice, the focus here is mostly on heavy metals, which have to be below certain thresholds. Special care has to be taken with pigments.

l Biodegradation: Evidence is required of degradation on a chemical or molecular level into carbon dioxide and water. This process starts at the composting stage and continues in the soil.

l Disintegration: On a physical and visual level, this complements biodegradation at a chemical level.

l Final compost quality: Ecotoxicity and plant growth tests have to be carried out, with other composts taken as a benchmark.