Recovering sugar from juice industry to make bioplastics
Four years of research have led to a biodegradable prototype juice bottle made from sugars recovered from wastewater from the juice industry. But will this become a commercial proposition, asks James Snodgrass in this feature for Plastics News Europe.
In the last 20 years the market for fruit juices, and blended drinks containing fruit juice, has rocketed, mostly at the expense of sugary, carbonated drinks because consumers have been looking for an alternative that is considered healthier and “more natural”.
The truth – as many dentists will attest – is that juices, even pure juices, are very high in sugar. It just so happens that those sugars are not the sucrose derived from sugar beet or sugar cane, but the fructose that naturally occurs in fruits and vegetables.
Making bioplastics from sugars is nothing new. It was once considered a radical, eco-friendly alternative to making plastics from fossil fuel by-products. But nowadays, with growing population and a planet that stubbornly refuses to enlarge itself to accommodate these people and their appetites, the notion of taking agricultural land away from food production has become as controversial as the continued use of petrochemicals.
Agricultural waste, therefore, has become the prime candidate for obtaining the sugars needed as precursors to bioplastics. But there’s a problem with agricultural waste. Much of the plant material that is wasted is the plant material that can’t be eaten. And the bits of plants that humans like to eat, tend to be the bits that contain sugars in their most easily extracted form.
But food waste happens during all stages of the “food-to-fork” cycle. And novel initiatives have been found to recover sugar-rich waste that might otherwise be discarded. One such initiative has recently been presented at an international workshop in Brussels, Belgium, by the Spain-based Ainia Technology and the European Fruit Juice Association (AIJN).
The PHBottle project, coordinated by Ainia, has been working to exemplify the “circular economy” concept promoted by the EU in its commitment for innovation and sustainable technological development, under the 7th Framework Programme. The international consortium includes AIJN, the Spanish company Citresa (a division of the multinational Suntory), Logoplaste Innovation Lab (Portugal), Logoplaste (Brazil), Omniform (Belgium), Sivel (Bulgaria) and the Mega Empack (Mexico) as well as the technology centres TNO (The Netherlands), Aimplas (Spain) and INTI (Argentina).
The PHBottle project has created a prototype bottle from sugars recovered from wastewater used in the juice industry, making what it calls “active bio-based packaging”. The project partners claim that 30% of the sugars from juice industry wastewater can be recovered and re-used.
The project participants claim that the prototype packaging presents the strength, stiffness, and antioxidant properties and other characteristic mechanical properties of a traditional package. Also, in biodegradability and compostability tests of the bottle it has been observed to degrade by 60% within nine weeks. By comparison, it will take almost 100 years for a petrochemical-derived plastic container to biodegrade. The PHBottle can also be decomposed in composting plants, to produce compost and, perhaps ironically, CO2.
The PHBottle project is the result of more than four years’ research by the international consortium. The bottle is made from polyhydroxybutyrate (PHB), a polymer produced by bioproduction (microbial fermentation) in which certain bacteria use the sugars in the wastewater and synthesise this type of bioplastic.
The consortium claims that the resulting bioplastic material has improved antioxidant properties which extend the shelf-life of the juice. Microencapsulation technology was used to produce capsules with antioxidants such as limonene, which is an active compound present in orange peel. These capsules were incorporated into the PHB compound used to manufacture the final bottle, creating an “active packaging” in which the antioxidant agent is slowly released, delaying the oxidation of the juice.
In addition to sugar recovered from wastewater, other types of food industry waste were used to improve the strength and other mechanical properties of the material. Cellulose microfibres were produced from rice hulls and incorporated to improve the rigidity of the packaging.
To emphasise the “circular economy” concept, the PHB bottle prototype was used to package the juice produced by the wastewater generating industry itself. It is also suggested that wastewater-derived PHB can be used in other industrial sectors such as cosmetics, ophthalmology, footwear, computer parts, pharmaceutical or automotive.
What exactly is the nature of the waste water from juicing? Ainia’s project coordinator, Dr Ana Valera explained: “The juice industry generates a lot of wastewater streams: for cleaning the fruit in different points, for cleaning the equipments used for manufacturing the juice, etc. In the project, we studied which stream was the most suitable one in terms of high organic load (sugars). The selected stream was one from the cleaning process after the juice manufacturing.”
However the project is still very much at the R&D stage and all the usual problems of preparing for commercial upscaling and meeting regulatory challenges will delay its entry into the marketplace.
Valera told Plastics News Europe: “PHBottle project has been an R&D project which means that the work was focused on research about the PHB bioproduction process using the wastewaters as raw material, about the final formula of PHB compounds for manufacturing the bottles using the current technologies in the plastic sector (extrusion-blow moulding, injection, etc.). All this work has been done at two scales: lab and pilot plant scale.
“This means that more work needs to be done for optimising the processes and getting competitive prices of the final product before jumping to the market. Furthermore, it would be necessary to have the approval of the European Food Safety Agency for our PHB as a food contact material.”
Once these hurdles are overcome, however, we could one day be drinking bottles made from the very drink it contains.