News Items - International Association of Packaging Research Institutes
Making ‘responsible packaging’ work

The theme of the May IAPRI Conference in Mumbai, India – ‘Responsible Packaging for a Better Future’ – could not have been better conveyed than by the numerous presentations focusing on bio-based, compostable and biodegradable materials.

While ‘sustainable’ may be the buzzword that featured in many previous IAPRI conferences (and indeed in this), one of the May keynote presentations picked out an alternative term that could soon become just as familiar. Under the title ‘Innovation at scale: regenerative packaging for a cleaner planet’, head of innovation at packaging converter Pakka Impact Ramjee Subramanian delivered a persuasive message about the industry’s direction of travel.
 
Having outlined recent developments in packaging technologies and consumer expectations, Subramanian went on to remind his audience of some uncomfortable facts about fossil-based plastics. “Current recycling rates have stalled at 9%,” he said. “There is more plastics in our soils than there is in our oceans – around 23 times as much; and five tonnes is the amount of carbon dioxide produced per tonne of plastics.”
 
He argued that the plastics industry alone was on course to use up a massive 15% of the global ‘1.5degC carbon budget’.
 
More broadly, he produced figures to show how the current 2.1 billion tonnes of waste generated annually around the world was due to increase to 3.4 bn tonnes by 2050.
 
A sustainable and regenerative model, on the other hand, would see zero waste, with materials and natural resources kept within ‘nature’s circular supply chain’, said Subramanian. “Radical rethinking is needed,” he stated, asking: “Are you in?”
 
His list of materials under the ‘regenerative’ banner included natural and microbial biopolymers, starches and polysaccharides, lipids, proteins and mineral composites. Pakka itself produces moulded fiber, carry bags and other packaging from sugarcane and other agricultural residues.
 
Stimulating PLA degradation
 
Among the ‘first generation’ biopolymers which have garnered the most research interest together with some commercial leverage over recent years, polylactic acid (PLA) stands out from the crowd. The biobased and biodegradable polymer research group at Michigan State University (MSU) School of Packaging has been examining different aspects of PLA and its biodegradation behavior in various environments.
 
At the Mumbai Conference, MSU’s Rafael Auras stood in for lead author Pooja Mayeka to present a paper looking at the use of bio-stimulation to accelerate the biodegradation of PLA in mesophilic conditions (typically 20degC to 45degC). As he put it: “Although PLA is compostable when subjected to a suitable set of conditions, in other words, aerobic, thermophilic conditions for an extended period, its wide acceptance in industrial composting facilities has been affected adversely due to longer degradation timeframes than the readily biodegradable organic fraction of waste mostly made of cellulose and starch.”
 
In this research, the biodegradation of PLA was monitored in a compost matrix kept at 37degC for 180 days, with bio-stimulation provided by skim milk, gelatin and ethyl lactate to enhance different stages of the PLA degradation process. Those stages are: chemical hydrolysis; enzymatic hydrolysis; bio-assimilation; and mineralization.
 
The research team monitored CO2 produced, using an in-house, direct-measurement respirometer, and the average molecular number, tracked using size-exclusion chromatography. Results showed that compost bio-stimulated with skim milk and gelatin enhanced the PLA’s mineralization by 35.7% and 13% respectively, and reduced by 53.2% and 61,7% the molecular number.
 
Evolution with no bio-stimulation at all was very different. “A long lag phase is observed for PLA without any treatment, indicating a slow hydrolysis phase,” said Auras. “This is depicted as negative mineralization over the test duration of 180 days.”
 
Alongside industrial composting, the practicalities of home (or backyard) composting have been much debated recently. As the MSU team pointed out in their paper, the low temperature range typically generated in this type of small-scale process means that PLA has not been certified as ‘home compostable’. PLA degradation in natural environments is also known to be slow.
 
The same MSU team has since published a further paper, this time examining the effects on biodegradation rates of blending thermoplastic starch (TPS) with PLA, together with a chemical modifier and peroxide radicals. The paper suggests this allows for successful composting within 180 days in both home and industrial settings. It can be accessed from the Recent Research Publications link on the IAPRI website – where other members can, of course, also submit a form regarding their own latest research.
 
Sugar solutions?
 
India’s Pakka Impact is not alone in working with sugarcane waste. At the Mumbai Conference, Cristina Guzman of the University of Monterrey (UDEM) pointed out India as one of four economies that have successfully developed commercial production of papers based on these raw materials. The other three countries are South Africa, Colombia and Argentina. Her paper explored and evaluated the feasibility of Mexico developing its own sugarcane-based paper industry.
 
In fact, the country is the sixth largest producer of sugarcane in the world, accounting for 4.6% of global production. At the same time, there would doubtless be strong demand for the end product. “Mexico does not have wood forests to produce paper,” said Guzman. “Most Mexican paper is recycled from imported paper and cardboard.” As a result, the resulting recycled paper and board tends to be of poor quality and strength, comprising short fibers. “Why not use another material source with longer fibers to improve Mexican cardboard?” she asked.
 
In sustainability terms, Guzman underlines another benefit of this agricultural by-product: the fact that it “doesn’t use any chemistry in its process”.
 
Having sourced its sugarcane bagasse sample from Veracruz province and used natural drying to prepare it, the UDEM team set about analyzing its components: lignin; cellulose; holocellulose; as well as total solids and volatile solids content.
 
Unlike some other analyses, this study found that the sample comprised almost equal proportions of lignin and cellulose (just over 28%). Typically, for paper manufacture, higher cellulose and lower lignin levels are preferred.
 
Of the different stages of the research, Guzman said: “This first phase was not positive for paper production, but the experiments were done just with the powder and not the fibers themselves. More studies need to be done with the current sample and with other samples from a different location.”
 
Pilot-scale films
 
If sugarcane by-products have a role to play in sustainable packaging, so to do those from wheat. Research carried out by a team from ITENE and IATA, Spain, and presented at Mumbai, looked at the use of gliadins – a component of wheat gluten. These proteins are said to offer good film-forming behavior, good adhesion to other surfaces, biodegradability and the capability to deliver bioactives.
 
Lead author Alejandro Aragon of ITENE explained that the thermoplastic gliadins (TPG) were blended with polycaprolactone (PCL) to produce films on a pilot-scale extruder, before being characterized by means of structural, morphological, thermal, mechanical and barrier tests. The aim was to assess the films’ suitability for food applications.
 
“Finally, the compostability of the films was assessed to determine the influence of gliadins on the biodegradation and disintegration rate of PCL under home composting conditions,” he said.
 
Increasing the proportion of TPG to 30% and 50% by weight saw a corresponding improvement of oxygen barrier, said the authors. But higher proportions of TPG also led to an increase in water vapour permeability.
 
The positive effects on compostability of including TPG were noticeable. “The presence of plasticized gliadins promoted an accelerated biodegradation rate with respect to pure PCL,” Aragon said. After 210 days, the 30% TPG sample showed an 89% biodegradation, taking microcrystalline cellulose as the reference material. After the same period, the 50% sample showed 96% degradation.
 
Meanwhile, a different team from ITENE worked on a project aiming to overcome the problems commonly associated with the good dispersion of microfibrillated cellulose (MFC) through a PLA matrix, trialling liquid feeding of MFC as a more effective alternative. The MFC was chemically treated to improve its hydrophobicity and compatibility with the biopolymer, said lead author Soraya Sanchez.  
 
Nanocomposites were obtained through both wet and dry compounding processes. “The results exhibited an improvement of the mechanical and barrier properties, reducing oxygen permeability by up to 13%, and water vapour permeability by up to 11%, in the PLA-based composites produced by the wet compounding process,” she said. “These results indicate the potential of these new materials with good barrier properties for packaging applications.”
 
While work with these ‘first generation’ biopolymers continues, with a focus on improving their performance in use as well as their biodegradability, it is clear that a new generation of biobased materials is offering new benefits – and challenges – of its own.
 

Published: 07/30/23