Written by Wymond Symes
It seems that the news has been full of stories recently about plastic pollution and the issues this is causing wildlife and the environment as a whole.
Here in New Zealand a big topic of the past month or so are pledges made by Foodstuffs and Progressive Enterprises to remove single use plastic bags from New World and Countdown supermarkets by the end of 2018. This has come about because of customer feedback and it is great to see kiwis putting pressure on retailers to rethink the way they source and provide bags for the merchandise they sell.
So, what will come of this pledge? What will replace the common petroleum-based single-use bags we have become so accustomed to in our supermarkets? This is the big question and one I hope Foodstuffs and Progressive Enterprises are considering carefully.
There have been numerous studies done on the environmental impacts of petroleum-based plastic bags compared to paper bag and/or compostable plastic bag alternatives, dating back many years. The most meaningful studies are those that consider impacts across the full life cycle of bags, from sourcing of the raw materials to manufacture, distribution, use and disposal. We call these “cradle to grave” life cycle impact assessment studies. And the results of those published may surprise you.
Across many impact categories, including energy intensity, global warming (greenhouse gas emissions, also referred to as the product’s carbon footprint), water use and eutrophication (nutrient loading of waterways), “conventional” plastic bags outperform others. But only when disposed of appropriately. What I mean by this is only when they are recycled at the end of their useful life. And herein lies the problem, especially for us here in New Zealand and for our friends in Australia. Infrastructure for soft plastic recycling – recycling of polyethylene-based plastic bags and plastic film – is lacking in most geographical areas and where services do exist they are not particularly convenient.
The Love NZ Soft Plastics Programme was launched in November 2015. Reliant on retailers providing recycling bins at their stores, and the collection services of REDcycle, the programme allows and encourages householders to divert all types of conventional oil-based plastic bags, including single use shopping bags, from landfill. Recovered bags are sent to RePlas in Melbourne where they are made into plastic products. The programme is currently looking for a processor in New Zealand.
The programme claims to have recycled 25 million plastic bags in 2016 (100 tonnes worth). This is 1.6% of the 1.6 billion plastic bags used last year in New Zealand.
A similar programme in Australia utilises 800 collection points nationwide and the services, once again, of REDcycle for collection and RePlas for processing. In addition, most supermarkets in Australia facilitate single-use shopping bag recycling by providing drop off bins and working with local service providers. A small number of councils in Australia accept plastic bags in their curb side recycling bins. Of the 3.9 billion plastic bags used in Australia each year about 3% are recycled through these schemes.
With this in mind, have the supermarket giants in New Zealand missed an opportunity here with their recent pledges? Would they have been better off to commit to keeping polyethylene bags and instead pledge to lobby councils around the country into providing curb side soft plastic recycling services and soft plastic recycling at recycling centres? The answer to this is not necessarily, and to examine it we need to understand how polyethylene bags “outperform” paper and compostable alternatives when they are recycled.
By recycling plastic into a second-generation product, we avoid the need to make that same product from virgin material. This is environmentally beneficial. Having said that, it is important to note that this “benefit” can be compromised if factors like where the recycling processes take place and the impacts of sending the used plastic there. For us in New Zealand much of our recycled material is sent to China (but maybe not for much longer, and that’s another story).
Add to this that, in the case of compostable plastic bags for instance, environmental comparisons with conventional plastic bags are not always done on optimised disposal options for the compostable bag, and you start to see it is not all black and white.
The performance of a compostable bag differs enormously depending on whether the bag is sent to landfill at the end of its life or is composted. In landfill compostable bags degrade over time to produce methane and carbon dioxide – both greenhouse gases that contribute to global warming, which is bad. However, many landfill sites in New Zealand and Australia now capture these gases and either flare them off or use them to generate biogas as a renewable energy source, which is good.
Composting these bags is generally good for the environment as nutrients are recycled, but the net benefit of this is also impacted by where and how the bag is composted. Not everyone does home composting and not all compostable bags compost in a home compost system. For bags not composted at home there is the need to transport them to a commercial composting facility, which adds “environmental burden”. Some commercial composting systems can be quite energy intensive, which adds further to the burden.
All this brings me back to my earlier point about the supermarkets needing to do thorough due diligence on alternatives to the status quo. There potentially is no clear winner when it comes to a bag for taking your groceries home in. In many ways it comes down to how the bags are disposed of and the convenience with which customers can apply the best disposal options. It will be interesting to see where the supermarkets go with this, and I hope that in coming up with an alternative bag they work with councils and other regional authorities to ensure infrastructure is put in place to allow bag users to dispose of their bags in a way that is most environmentally sound.