2 July/August 2019 Recycling Aerosol recycling: past, present and future Key developments in aerosol manufacturing could pave the way for record recycling rates Methods of recycling aerosols have come a long way since the product’s commercial introduction in the 1930s. In this article, Mike MacKay of DeSpray Environmental discusses the trials and tribulations of finding sustainable solutions to spray can recycling.
Past
Taking into consideration that aerosols were introduced as a viable commercial product for consumers in the 1930s and 40s, it is no surprise that almost no recycling technology existed or was even thought about at that time. There was no way to predict the amazing growth and environmental impacts of spray cans with the science and technology knowledge of the time.
To consider the massive public acceptance and growth of this invention, and subsequently the environmental impact, was an afterthought at best. Back in those days, buzz words like sustainability, circular economy, environmental impact or even ‘recycling’ or ‘green’ were not used in the public vocabulary without an eyebrow being raised. To consider the environmental impact of aerosols beyond a vague knowledge of landfills would almost surely label you as a non-conformist or ‘tree-hugger’, standing in the way of modern progress. Besides, where was the proof? It simply wasn’t cool to be an environmentalist and nobody believed that humans could possibly hurt our planet.
Landfilling or, in very rare cases, shredding these spray cans to capture the metal seemed futuristic. After all, what damage could these cans possibly do once captured in landfills and buried for all of eternity, never to be witnessed by humans again? So, bury them we did! Problem solved.
But then came the 1970s and 80s, when undisputable research was undertaken on the diminishing ozone layer. People took notice and the aerosol filler industry responded immediately. Production of chlorofluorocarbons (CFC) propellants that were contributing to dissolving the ozone layer was stopped immediately, and we can be proud of the fact that the ozone layer is expected to make a full recovery by 2030. This is an amazing result.
Then, best practices moved from CFC filling to other propellant gases. Notice was taken by both the filling industry and the recycling industry, and propellants advanced to hydrofluorocarbon (HFC) gases along with other propellants that are non-HFC, as well as non-propellant spray methods such as bag-on-valve (BOV). Recycling methods also advanced from landfilling and shredding only, to other methods such as emptying the contents via the nozzle before discarding or even puncturing the cans carefully to release the gases and liquids to the atmosphere. Or, better yet, using carbon filtering by running the gases through carbon beds.
However, considering that one cubic metre of full spray cans could contain upwards of 150kg of liquid gas, carbon beds would not only be non-effective but also non-feasible from a cost or effectiveness perspective. The size of carbon beds needed to properly capture the gases and versatile organic compounds Despray Containerised 100% recycling system. Designed and manufactured by MachineFabriek Boessenkool NL Mike MacKay, managing director at DeSpray July/August 2019 3 Recycling (VOCs) from even a small waste stream of spray cans would have to be immense, along with sizeable regeneration or replacement costs and volumes. It would be impossible to carbon-capture the gases and, even if it were possible, the costs would be extremely prohibitive. Now if we just concentrate on metal recycling, perhaps all would be well in the environmental world of aerosols.
Not so fast. First of all, aerosol cans are almost never empty. Secondly, the customers releasing the contents of an aerosol or the contents being released as a result of factory defects aren’t the only environmental issue. Moreover, safety concerns are still not mitigated by BOV or non-HFC gases. The contents themselves can be flammable, and many BOV products also contain alcohol, creating a potentially false sense of safety when using BOV or other propellants.
Twenty years of industry data suggests a combination of manufacturing discards, commercial shelf-clearing and postconsumer waste combine for an aftermarket of over 5-10% of contents and gases remaining in the cans. To ignore proper recycling of the post-consumer waste stream simply because best methods are convenient is irresponsible. They may not seem like much of a burden, but when we multiply the effects by 15 billion – the number of aerosols available for recycling in 2018 – this stream warrants making some changes to our way of thinking. ‘Out of sight, out of mind’ is a thing of the past. Shredding, baling and puncturing are no longer acceptable recycling methods and are certainly not best practices.
Present
The ever-growing pressure from a health and safety perspective, as well as global environmental awareness and corporate image, is driving every industry to be more sustainable. The aerosol filling industry is no exception to this and, in fact, is ahead of the curve. For modern-day recycling and sustainability expectations to be met in the aerosol business, both best practices and our way of thinking had to change.
In order to meet all environmental responsibilities, all three streams (propellant gases, liquid contents and metal) need to be considered – a formidable task, but not an impossible one. The filler industry already has one of the best sustainability report cards of any industry based on current technologies, corporate environmental footprint and recycling in general, as far as spray cans and metal cans are concerned. In some regions, for example, metal spray can recycling figures are as high as 90%. While it’s great to report those kinds of recycling numbers, the task of capturing the contents and the propellants for reuse has to be considered before these cans can be processed for recycling.
Current recycling methods do a great job of de-packaging the cans to prepare the metals for 100% continuous recycling, but fall short for the liquid contents and gases. Unfortunately, many recycling methods, including baling and shredding, do not deal with the liquid contents of the cans and the propellant gases. They are simply disregarded and disappear into the atmosphere, ultimately creating greenhouse gases. In order to capture both of these potentially dangerous substances, spray cans need to be treated differently from simple metal cans. To achieve this goal, the contents and propellants require a closed non-oxygen atmosphere to ensure the gas is captured, while guaranteeing safety for recyclers and their employees. Most current Liquid Carbon Capture Gas Gas Liquid Gas Gas Liquid Metal Brick Aerosol Waste Liquid Gas Aerosol can-crushing recycling system Zero Emission www.DeSpray.Com Waste to Energy Satellite liquid accumulation tank Propane/Butane collection tank Compressor Gas to Energy Waste to energy Dense, dry metal bricks ready for recycling 4 July/August 2019 Recycling methods do a great job of separating the metal from the liquid and gas and converting the waste into manageable metal bales or shred. While this is a considerable improvement on landfilling, it falls short of preventing environmental contamination and greenhouse gases. These methods also have the potential to cause fires, or even explosions. The good news is that new technology can recover the gases and metals to achieve 100% recyclability.
Technology
Safe and sustainable technologies are now available and quickly gaining popularity. These technologies can boast 100% recycling, but they have to take into consideration fire hazards, explosive environments and mixtures of propellants, as well as siloxanes and impurities in the gases. This would obviously increase the cost of recycling, which is the largest barrier to market penetration. Consumers are getting much more accustomed to paying deposit fees or recycling fees as high as 10 cents (€0.08) per can for metal soup, soda and beer cans yet there is no similar fee for aerosols. Considering that aerosols have a significantly higher environmental impact than these simple cans, this lack of deposit or responsibility fee does not make sense. A deposit would have a huge impact if it went to the recycler that is processing responsibly.
This is a worldwide phenomenon that is fortunately changing due to corporate responsibility and sustainability, along with public environmental pressures. The technology exists; we just need the mindset to pay an appropriate price to ensure that we are doing our part to guarantee the use of proper recycling methods.
Compacting the spray cans in a closed non-oxygen environment is achievable with internal oxygen-monitoring sensors and full nitrogen control, to ensure a non-explosive atmosphere of less than 4% oxygen within the closed crushing core. With these technologies, when the oxygen level rises above safe operating levels, the machine automatically stops to allow the nitrogen to bring the enclosed atmosphere back under safe operating parameters. It should also be noted that the liquid contents capture suspended propellant gases. By controlling the closed-loop atmosphere of the recycling system, these elusive suspended gases can be off-gassed internally and recompressed back to liquefied petroleum gas (LPG) along with the main gas propellants.
It is possible to achieve 100% spray can recycling. While balers and shredders are able to capture the metal, they side-step the toughest aspects: the gas and liquid contents. These existing technologies do a great job of recycling the metal, but they have two inherent problems:
- Safety is compromised. Aerosol cans that are considered empty can still be at risk of exploding. Historical data suggests that 5 to 10% of the liquid and gas contents could be present at end of life. These numbers are a combination of factory rejects, post-consumer use and commercial returns. Processing these cans in standard recycling equipment could result in fires or explosions, putting employees and valuable assets at risk.
- Gas and liquid contents are not captured and are subsequently released into the atmosphere through recycling. Even at low numbers, this environmental impact would be significant when multiplied by 15 billion. When recycling aerosols, all three components (propellant gases, liquid contents and metal) need to be considered. Even landfilling eventually breaks down the cans and releases the contents to the environment.
Future
Although 100% recycling technology exists, the future of aerosol recycling still has many hurdles to overcome, including corporate practices, public awareness and appropriate price levels. The good news is that these obstacles can be tackled in the very near future.
- Mixed gases: Capturing mixed gases and compressing them to LPG creates a lower-grade fuel that leaves siloxanes and odor traces in the gas. These siloxanes make the gas prohibitive for waste-to-energy due to a calcium-style build up that occurs when burning in standard piston-style engines and turbine generators, rendering them inoperative over time without continuous maintenance. Fortunately, full production testing is in progress that could remove over 95% of siloxanes from the gases. This siloxane removal is expected to transform the LPG into a cleaner high BTU-grade fuel that can be used to convert the otherwise unusable waste into full electrical energy in standard generators. This technology is a game-changer and is one of the final technical hurdles to be able to claim full waste-to-energy. Full production trials are expected to start as early as September 2019.
- Expandable foams: One of the aerosol industry’s greatest recycling challenges is polyurethane (PU) or expanding foams. These infamous PU foams are a recycling nightmare. Thankfully, a solution is on the horizon. Preliminary laboratory testing on new technology has proven successful in low quantity test runs. This new technology will be able to safely process expandable foam cans effectively and automatically in a specialized aerosol recycling machine. The foam would be internally processed into a manageable waste stream for further waste-to-energy while the metal is formed into dense bricks. Further testing will be completed within the next few months, which will lead to the possibility of the development of a fully-operational production-style foam can recycling system with 100% safe recycling capabilities.
- Plastic cans: There are currently no methods available to continuously recycle plastic cans, while cleaning the plastic for reuse and capturing the gases and degassed liquids. This may be possible, but not without challenges. For example, one of the sorting issues will be how to separate these cans from plastic soda bottles. This is not impossible; however it adds another level of complexity that needs to be addressed.
- Metal: Metal is a continuously recyclable material. The not-so-distant future may include aluminium or steel caps nozzles and even straws in lieu of plastic. Who will be the first to offer the consumer this environmentally-friendly option?
Stay tuned for future aerosol recycling developments. The future looks bright. Post-consumer spray cans ready for processing