One Page Summary

Rationale
Paper has excellent properties as a packaging material. It is light, recyclable, and can be manufactured from sustainable sources. However, despite being on the market since even before the dawn of plastic polymers, currently available paper bags cannot be an alternative to plastic produce bags because of their poor mechanical properties (especially in contact with wet materials), high permeability to liquids (including water, external contaminants, and grease from fatty foodstuffs), and elevated cost. Paper can be laminated with compounds such as paraffin wax or plastic to make it strong enough to fulfil the technical functions of a produce bag and avoid any substance transfer between food and bag. Unfortunately, until now, this was not an acceptable solution because those coating materials are petroleum-based, having similar waste disposal problems than conventional plastic bags. Paraffin waxes and plastic films are difficult to separate from the paper fibre and, in most cases, they are left out of the recycling stream to avoid contamination that results in unacceptable batches of recycled paper and damage of the recycling equipment. As a consequence, they are usually treated as urban solid wastes, contributing to climate change, and polluting air, agricultural lands and aquatic environments. Also, some per- and polyfluorinated compounds used in surface functionalization of paper packaging are carcinogenic for humans. Nonetheless, these polluting compounds can be substituted by environmentally-friendly, fully biodegradable biopolymers, which can be sourced from sustainable stocks and provide similar technological properties than the plastic-based coatings.

Solution
Our solution consists in creating on the paper surface a composite thin coating made of a blend of hydrophobic and natural polymers approved as food contact materials such as ethyl or methyl cellulose and beeswax, which have the film-forming capacity. Precise control of the biopolymer blend and the use of techniques like casting, lamination, ultrasonic spray coating or electrospray will allow fine-tuning the coating characteristics to improve the barrier and mechanical properties of the paper bags, making them suitable to hold any foodstuff. Additionally, some biopolymers such as cellulose, alginate or chitosan can also be engineered to produce aerogels, which are porous ultralight materials derived from gels, in which the liquid has been removed by drying under supercritical conditions, resulting in solids with ultra-low density and extremely low thermal conductivity. We will produce them at the microscale, so we can create a homogeneous super thermal-insulating layer, making the paper bags suitable to keep frozen and refrigerated foodstuff at an appropriate temperature during their delivery. The result of combining both approaches, hydrophobic and a thermal-insulating layer, will be a safe, affordable, sustainably sourced, recyclable, and fully biodegradable bio-based paper bags suitable for packaging dry, wet, or fatty foodstuff, either at room temperature or from refrigerated or frozen storage.

Impact
The implementation of the proposed solution in the retail sector would allow a total replacement of the petroleum-based plastics bags for improved paper bags without losing any functionality as packaging material. Additionally, some extra benefits can be expected: as the new paper bags can be sourced from sustainable materials, and will be fully recyclable or compostable, they will not pose any harm to the environment.

Implementation
We will first select a set of natural biopolymers and optimise a blend of them able of forming hydrophobic films that will be used to produce the water barrier of the bag.
In a second phase, we will produce micro-hydrogels from biopolymers, and transform them into micro-aerogels that will provide super thermal insulation and a barrier for grease, fatty compounds, and organic contaminants.
In a third step, we will design a composite made of an optimised blend of hydrophobic biopolymers and micro-aerogels and a coating protocol compatible with the current paper production processes.
Finally, we will produce the coated paper bags according to the optimised specifications and, in collaboration with SONAE, we will perform a trial to assess the performance of the enhanced paper bags in a real market situation.

Capacity
INL team has extensive expertise developing solutions based on biopolymers for different food packaging applications. Active (antimicrobial, antioxidant) and edible films were developed in the framework of several national and European projects such as the H2020 YPACK Project. INL team is currently developing an antimicrobial cellulose paper under a Research Contract with The Navigator Company. INL has the infrastructure required for developing the project at pilot scale (approx. 100 units of the new bags). Should more bags be needed, we will outsource the manufacturing to our industrial partners.