New generation is growing up fast - Coca-Cola's PlantBottle
Coca-Cola’s 100% bio-based bottle could soon be a commercial reality. But, as Paul Gander finds out, the different technologies being pursued face significant challenges.
If you still think of sustainable packaging as being something simple, think again. The latest developments around Coca-Cola’s bio-based PlantBottle demonstrate that the science, as well as the choices, involved in creating eco-efficient solutions can be as complex as anything in traditional polymer engineering.
In its latest PlantBottle initiatives, the soft drinks multinational is exploring a range of challenging routes towards the replacement of fossil fuel-derived plastics. What the routes have in common is a reliance on renewable resources. PlantBottle Packaging General Manager, Scott Vitters, makes clear that this strategy is driven by hard economics. ‘When it comes to managing our costs with plant sources, long-term, we have more confidence in this than in being able to manage fossil fuel costs,’ he says.
With its first-generation PlantBottle, introduced in 2009, Coca-Cola and its partners achieved a 30% proportion of PET from plant sources. This was based on bio-based monoethylene glycol (MEG), contributing the ethylene side of the equation. But it still left the drinks giant needing to crack the second part of the equation. The three projects announced at the end of last year, with Dutch company Avantium and with Gevo and Virent in the USA, each propose a different solution.
For Avantium, this means pursuing furanoates, aiming to produce polyethylene furanoate (PEF) as an alternative to PET. Like Avantium, Gevo uses fermentation, this time as the first stage in the production of bio-isobutanol. This is subsequently converted to paraxylene and (pure) terephthalic acid (PTA) for the production of PET. Virent also aims to produce precursors for PTA, in this case creating bioparaxylene using a chemical catalyst. At Virent, Director of Chemicals Kieran Furlong makes the point that it intends to use the cheapest and most widely available plant-derived material as feedstock. Given the current lack of infrastructure for collecting various kinds of crop waste and by-products, raw materials will initially be traditional crops. But longer-term, various types of cellulosic waste could be used.
Vitters at Coca-Cola draws a similar contrast. ‘First-generation feedstocks have been fed on other starches,’ he says. ‘But this will not be sufficient in the long-term. Our second-generation focus is expanding on the basis of using biomass and plant waste.’
Sustainability criteria, he makes clear, stipulate that raw material sources would not be permitted to compete with food stocks, either in terms of products used or of land use. The same would be true of social sustainability criteria. ‘There is no ultimate feedstock,’ he says. ‘It will be whatever improves both the environmental and social performance of a given process.’ In the USA, this might mean the use of corn or wheat waste, or even tree bark, Vitters speculates. But elsewhere in the world, raw materials could include rice waste and sugar cane bagasse. Whatever the types of feedstock used, the issue of efficiency is certain to loom large, particularly as the various technology providers work at differentiating their approaches.
The Virent process requires oxygen to be split from carbohydrates to generate hydrocarbons, including its own BioFormPX version of the aromatic hydrocarbon paraxylene. On the question of efficiency, Furlong argues that the company’s use of a catalytic process rather than fermentation means that carbon is not diverted into the production of CO2.
Gevo, for its part, puts a rather different spin on questions of yield and efficiency. Business Development Director Bob Bernacki points out that paraxylene is just one of the outputs of Virent’s process. ‘Our technology takes a fairly selective route to production, so that at least 95% of final output is paraxylene rather than other products,’ he says. That route follows the Gevo Isobutanol Fermentation Technology (GIFT) to bio-isobutanol. This in turn is the precursor to three chemical processes that finally produce paraxylene.
‘The process of obtaining isobutanol via fermentation is one of the highest yields you can get,’ says Bernacki, although he cannot comment on relative efficiencies in terms of the amount of feedstock required to produce a given amount of product.
‘It is estimated that demand for paraxylene is going to double between 2010 and 2020,’ says Virent’s Furlong. ‘Even if bio-based sources were contributing 10% of that demand, we would still require the equivalent of 30 new full-scale plants of our BioForming process.’
New material of choice?
If there is room for new sources of PET, it could be argued, there is potential for new polyesters such as PEF. This polymer has been known about for decades but was never considered cost-effective to produce.
Key attributes of PEF already mark it out as a potential favourite throughout the supply chain. It boasts six times the oxygen barrier of PET, three times the CO2 barrier, melt temperatures around 30°C lower but heat tolerance in pack form of up to 10°C more than PET. But Avantium MD Tom van Aken says, ‘One of the concerns voiced by Coca-Cola was that PEF would turn out to be another PLA’. What does he mean by this? The fortunes of PLA in bottle applications were adversely affected, particularly in the USA, by worries that it could contaminate and compromise otherwise successful PET recycling streams.
Avantium and Coca-Cola are pursuing tests on different proportions of PEF in PET recycling feedstock. To date, trials have been inconclusive. Coca-Cola advocates the co-existence of PEF and PET in this context.
All three technologies share a conviction of their own cost-effectiveness – at the appropriate volumes. ‘We will need to compete with petroleum-based PET,’ says Avantium’s van Aken. ‘If our process was on that same scale we believe our prices would be comparable.’