Developing a sustainable solution to recover multi-material films will require solutions across all phases of the recovery system
In summarizing the key findings found in the final reports issued by the various collaborative projects, key lessons and next steps begin to emerge which offer a promising roadmap towards sustainable recycling solutions for multi-material flexible packaging.
It should be noted that none of the projects looked at multi-material flexible packaging independently. Plastics were often aggregated in order to establish the volume needed to meet processing demands.
Design for Recovery Insights
- Compatibilizers can be used with polyethylene (PE) based multi-material films. This technology is now available directly within the film. This simplifies the recycling process as it prevents processors from needing to know film compositions to estimate compatibilizer amounts and permits for recycling directly with existing polyethylene streams.
- Since emerging data is suggesting post consumer multi-material flexible packaging may eventually be collected and sorted through a curbside system, a few observations were noted in how well package design interfaced with optical or near infrared (NIR) sorters:
- High glossy surfaces should be avoided as these are too difficult for optical sorters to recognize.
- Black or very dark objects may not provide enough light for optical sorters to recognize.
- While the Energy Bag projects offer promise in aggregating the collection of hard-to-recycle plastics, and suggest that bagged plastics can be collected curbside, the Materials Recovery for the Future (MRFF) report suggests that a loose automated collection process, similar to current single stream collection, has more potential to be scalable and cost effective than bagged films - particularly with large-scale MRFs.
- As we have seen with other recycling programs, engaging consumer participation is key to ensuring participation and quality. An increasing number of studies on recycling behavior for plastics and other materials, reinforces the need to provide clear and easy to understand messaging through a multiple of channels. Additionally, the use of images is highly recommended.
- The Flexible Aluminum-Containing Laminate trial suggested the generation of aluminum specific packaging may be too small in volume to warrant inclusion into consistent curbside collection programs.
- Consumers in the Flexible Aluminum-Containing Laminate trial noted odor and effort with washing as a disincentive to recycling food based packaging.
- While some flexible films may clog disc screens, multi-material flexible packaging does not appear to pose a challenge.
- All studies confirmed that the two dimensional nature of multi-material flexible packaging creates a natural flow within MRF sorting lines towards paper streams. Ejecting these from the paper stream is likely where the best solution for sortation may be found.
- There are a variety of existing and emerging technologies which offer significant promise for sorting multi-material flexible packaging along the MRF sortation line. Recommendations for further testing were encouraged. Promising technologies include the use of:
- Near infrared (NIR) optical sorters to detect multi-material films.
- Optical sorters to direct plastics, combined with the use of air flow, to eject films towards an independent collection point, is a promising format for films of all types.
- The use of a digital watermark on packaging, which would be undetectable to the human eye, but could be read by optical sorters demonstrated much promise.
Although these technologies offer potential promise for sortation, the economics of end market sales will dictate their long-term adoption.
- Odor and leakage from residual food packaging may be an issue when accumulating and storing materials for sale to recyclers.
- Polyolefin multi-material flexible packaging can be mechanically recycled, however much of the multi-material flexible packaging is not currently marketable to end markets because the multiple resin makeup weakens end product value. Alternative recovery methods to recycling should be considered for these materials.
- Currently, there is no large scale operation available to create end products from multi-material flexible packaging. While some pilots offer promise, further research estimating and understanding end markets for multi-material packaging would help develop interest and funding for end market development. The Closed Loop Foundation, and their offshoot Closed Loop Partners, has started this process but more is needed.
- In discussing alternative strategies to recycling with consumers, consumers prefer the concept of conversion-to-energy over conversion-to-oil or fuels. Conversion-to-energy also offers more flexibility should waste-sheds not be able to meet volume needs or quality requirements needed to operate pyrolysis or gasification facilities.
Processing and End Markets
These findings suggest there is a future for the recovery of multi-material flexible packaging, but that significantly more investment, research and innovation is required. Long term viability will be dependent upon the development of viable end markets. Most of the efforts to-date have increase our understanding of best practices in collection and sortation, but all identify that significant more work needs to be invested into developing economically viable end markets. Once a robust revenue source is established for post-consumer multi-material flexible packaging, it will be easier to justify the investments required to drive further collection and sortation. When assessing those end markets however, the SPC urges a careful consideration of the cumulative environmental impacts required. The most sustainable solution will be a cost effective solution which recovers the greatest amount of material with the least amount of resources.