Single use plastic bags are made of HDPE. This is a very pure compound made up of just carbon and hydrogen in a linear chain. It is not toxic. Its basic building block is ethylene (this occurs naturally in plants). To produce HDPE, ethylene is formed into long chains, which are very stable. Along with PET, HDPE is one of the two plastics that you can still recycle in New Zealand. If you burn it you produce carbon dioxide and water.
"Every piece of plastic ever made is still with us"
This well-worn phrase is not actually true. Plastics eventually degrade to smaller molecules (mostly carbon dioxide and water). Their speed of degradation is dependent mainly upon the wall thickness of the product they are made into.
"Plastic bags take a hundred years to degrade"
Thin film HDPE is an engineering miracle. With a wall thickness of less than the width of a human hair, an HDPE bag can easily hold one and a half thousand times its own weight. Pound for pound this makes them an incredibly efficient product. The long carbon chains in HDPE not only make it very strong for its weight, they also make it hard to break down. Having said this, there are organisms in the environment, both bacteria and fungi, that can metabolise it. It is not dissimilar in its chemical composition to bees wax. Modern production of HDPE uses additives that form weak points in the carbon chains, that react with sunlight to break the chains down into much shorter lengths. So, above ground (in the presence of UV light), it begins to degrade quite rapidly. This is helped by the fact it is a thin film (around 13 microns in thickness). The smaller the pieces become, the easier it is for microbes to digest them. It can't get into our food chain, because if ingested by an animal, it can't pass from the animal's gut to its tissue. When degradation is complete (called mineralisation), the two chemicals you end up with are CO2 and water.
"Huge numbers of plastic bags end up in the environment and cause pollution"
Many countries, especially in third world, have poor or non-existent waste management systems. A recent scientific study has concluded that up to 95% of all oceanic pollution originates from 10 large rivers of the developing world. This does not mitigate our responsibility, but It does make it possible to calculate New Zealand’s contribution to oceanic pollution. Although we are led to believe that our use of “single use plastic supermarket bags” was a large contributor to global oceanic pollution, the facts do not bear this out. New Zealand is a first world country and does a very good job of ensuring the vast majority of our domestic waste ends up in landfills. And, of the small amount of litter that gets into our environment, “single use plastic bags" made up just 1%. Interestingly, 40% of our environmental litter is fast food wrappers. It is not absurd to infer that most plastic bags that made it into our environment came from fast food outlets. Which is not a particularly convincing reason to ban supermarket bags.
"Plastic bags kill marine animals"
If you Google search pictures of The Great Pacific Garbage Patch you will find a striking absence of plastic bags. What you will find are a lot of bottles, and bottle caps. All the studies we have read regarding deaths of marine animals by ingestion, blame hard plastics. Plastic degradation is slower in the ocean due to lower temperatures, but relative to thicker plastic, thin walled plastic bags degrade much more quickly. HDPE has a specific gravity is around 0.95, so it floats on or near the surface where it is exposed to sunlight (see above).
Plastic bags are not known to kill marine animals by entanglement. Here is a quote attributed to David Santillo, a senior biologist with Greenpeace, to The Times of London, "It's very unlikely that many animals are killed by plastic bags. The evidence shows just the opposite. We are not going to solve the problem of waste by focusing on plastic bags. With larger mammals it's fishing gear that's the big problem. On a global basis plastic bags aren't an issue."
There is documented evidence that pieces of soft plastic have been ingested by sea turtles. Their known preference is for rubber balloons and clear/translucent plastics such as cling wrap. Studies of our coastline have determined that the known death rate of sea turtles in New Zealand by ingestion of plastic, is two animals per year. However, the information available does not, unfortunately, specify whether these deaths are due to hard or soft plastic. However, comprehensive international studies show that the majority of turtle deaths caused by plastic ingestion are due to hard plastic. The same is true for sea birds.
If even one sea turtle was killed by ingesting a plastic bag it would be tragic. However, the threat of extinction seems much more likely from other causes. The fishing industry kills hundreds of thousands of turtles annually in gill nets and on long lines. People still hunt them for their meat, eggs and shell (for jewelry). Human population growth is encroaching on their breeding grounds, and global sea level rise is eroding their nesting beaches. (Interestingly, unlike most vertebrates, sea turtles do not have sex chromosomes. The sex of their young is determined by the temperature of the sand in which they lay their eggs. A few degrees temperature rise could mean no males are born to continue the species. So a pressing issue in their preservation is control of Global Warming).
"Single use plastic bags were still a massive environmental problem. We used a billion a year"
Recent landfill statistics give us a very accurate picture of what we are consuming by measuring what we are throwing away. So what percentage of landfill is taken up with plastic bags? Plastic waste account for 12.1% of landfill. Roughly half of this (6%) is soft plastic. "Single use plastic bags", however, were just a small fraction of this total. There is an often quoted figure of one billion bags used by Kiwis every year. This may be a little on the high side, but if we use this figure, we can determine the percentage of landfill taken up with single use plastic bags. The average supermarket bag weighs around 5.5 grams (we will call it 6 grams). 1,000,000,000 x 6 grams = 6,000,000,000 grams = 6,000,000 kg = 6,000 tons. Six thousand tons of plastic sounds like a huge quantity but, to our shame, we currently send to landfill around 3 million tons of waste annually so, as a percentage, single use plastic bags made up approximately 0.2% of this total. Less than one quarter of one percent.
"When you put plastic in a land fill it takes a thousand years to break down"
Below ground, deprived of oxygen, HDPE is inert. Similarly, if you send concrete to the landfill, it will remain there, inert. It is strange that a different standard is placed on these two substances. Both have been extracted from the ground, chemically modified and returned to the ground. The main difference is that the lump of concrete will still be a lump of concrete in a billion years. (The plastic bag and its contents may quite possibly have turned back into crude oil).
In truth, if you have to put something in a landfill, you want it to remain there, inert and unchanging. Burying things is not a new practice for humans. If you dig down in the centre of London, you will find evidence of Roman habitation 40 feet below ground. Everything above that was deposited by humans. The argument that HDPE is bad because it is a man-made substance must also be applied to concrete; used by the Romans in ancient London (though invented much earlier than that *). As far as we are aware, there is no environmental group advocating a ban on dumping of concrete in landfills.
"Plastics are a petroleum product so they contribute to Global Warming"
When petroleum products are burned, their carbon content is dispersed into the atmosphere as CO2. When crude oil is turned into plastic the carbon is trapped. If the plastic is burned, its carbon content is released into the atmosphere, but if it is buried, the carbon remains trapped.
Incidentally, if you have ever got close to a jar of crude oil you will know that it is pretty disgusting stuff, for something made by nature. The hydrogen sulfide it gives off, which smells like rotten eggs, can actually kill you. It’s lucky that most of it is buried deep underground. If it was possible to turn all of it into inert HDPE and re-bury it underground the world would, arguably, be a better place.
"I don't care what arguments you put forward, plastic bags are just evil"
“Single use plastic supermarket bags” are a tiny subset of all the plastic we use. So, why do we all share a bias against them. We all like to believe that we reason with our frontal lobes, but every decision must pass by our amygdala, the part of our brain that registers fear and disgust. Through many years of subtle indoctrination, “single use plastic bags” have become somehow the embodiment of the disgusting way we treat our planet. When you think about plastic bags you may well think of stinking landfills, or dying sea turtles. But “single use plastic bags" haven’t just fallen into this role. Decades of visual imagery has seared into our brains an association with death and decay and profligate waste. Even the term "single use" is a misnomer, because almost all are used at least twice. But whenever they are discussed in the media, they are never thoughtfully re-purposed, they are "discarded". Next time you see a news article about oceanic pollution, no matter what kind, it will almost certainly be accompanied by a picture of a “single use plastic bag”.
We could quite easily have chosen “single use plastic drink bottles” instead. What is the difference between them? One answer could be that “single use plastic bags” have no strong pro-lobby group. “Single use plastic drink bottles”, as a sub-group, is far more detrimental to the planet than “single use plastic bags”. Their wall thickness is around 50 times that of HDPE film which means they remain intact in the environment far longer. They can be found in their millions in the Great Pacific Garbage Patch and on the shores of Midway Island at its centre, and their bottle caps in the stomach contents of the resident dead albatross chicks. So, why is it these more worthy candidates haven’t come to symbolise our profligate Western lifestyles. One reason is that they have a strong pro-lobby in drinks manufacturers, who constantly bombard us with advertising images associating drinking from them as a joyful, beautiful, life-affirming act. Just as with “single use plastic bags”, its all in the marketing. If you think about it, in the developed world at least, “single use plastic bottles” are completely unnecessary. Everyone in New Zealand has ready access to clean drinking water. Would banning “single use plastic bottles put such a crimp on our decadent western lifestyles? If it was a choice of banning one or the other, perhaps we should keep the one that actually performs a useful function. Of course, it is not as simple as making a choice between banning one thing or another. Every choice we make affects our planet.
If you have read this far down the page, you are obviously interested in saving the Planet, but you may be more confused than ever. So what can you do to help? Here are 4 simple things you could start with:
Stop buying stuff you don't need. (Clothes, as an example - textiles make up around 4% of landfill waste. If you are interested, Google search Fast Fashion and why it is killing our planet).
Stop buying bottled water, or anything else that comes in a single use plastic bottle. Just Google a picture of Midway Island and you will see just how long they can last in the environment. If you want to get really depressed, look at the pictures of the decaying bodies of albatross chicks and see how many bottle caps you can count.
Most importantly, buy a green waste bin and use it for everything compostable that leaves your home.
If you don't live in an area where your council offers a green waste collection service, find a private one. Not only will you be reducing your harmful greenhouse gas emissions (around 4 tons per household per year), you will be helping to more than double the useful life of you local landfill. By the way, the reason it is not possible to build houses on a landfill immediately after decommissioning it, is less about what it seeping out of the bottom of it than what is seeping out of the top. Methane continues to gas-off for decades.
Agitate with your local council to use recycled plastic products instead of treated timber so that the supermarkets can continue their soft plastics collections.
Then …
Spread the word to your friends and family. Tell them what you are doing and why, and remind them that you are doing it for their children and grandchildren.
"But I would like to do more"
Great. Start a community group. Push for your local council to supply optional green waste bins to all households. If you want to get militant, insist that these green waste bins be compulsory for every household. Once you have achieved that, think nationally. Start writing letters to your local MP. Get the rest of your group to do the same. Together, with small steps, we can make a huge difference. Here is an example:
eugenie.sage@parliament.govt.nz
Dear Eugenie
I have learned that in New Zealand we are presently sending massive quantities of biodegradable material to landfills in the form of domestic green waste and kitchen scraps. Magnified by its conversion to methane, this is a significant contributor to Global Warming.
I would like you to consider a law making it compulsory for all Councils to supply separate green waste bins to every domestic dwelling in New Zealand.
Yours sincerely
"Why is there so much misinformation on the internet? How can I get the truth?"
Arm yourself with a little knowledge. Saving the planet is not rocket science, but it is science.
Google searches rank by popularity, not plausibility. Think about the wording of your search choices. If you type in “911 was a conspiracy”, then conspiracy is what you will get. Check every source. Verify facts. On matters of science, look for well known organisations, who publish peer reviewed studies. And please think before you “like” or “share”. The uncritical repetition of improbable facts makes us all more ignorant.
Ask, does this group have an agenda? For example, the information you are currently reading comes from a site that sells plastic bags. Why should you trust what is said here?** Companies wanting to sell you stuff, and even some environmentalists pushing a particular agenda, can bend the truth. (see the TED talk at the very bottom of this page)
And it is possible to lie by omission. Retailers who tout cornstarch or paper waste bags as an alternative to HDPE, tell you they are better for the environment. However, they neglect to mention that, unless you compost these bags yourself, they will almost certainly end up in a landfill, where they will produce methane, which is incredibly bad for the environment.
** An explanation as to why you might be able to trust what is being said here (though we strongly recommend you conduct your own independent research) is that we sell dog waste bags, so until the general public can be convinced to pick up dog poo with their bare hands, dog poo bags will be exempt from any proposed ban. However, now that all “single use plastic supermarket bags” are banned, we gain financially, because a lot of people previously reused their supermarket bags to pick up poo. So why did we defend supermarket bags? Because fixing problems requires us to base our reasoning on facts. Banning these bags was illogical and has created more problems than it has solved***.
And the conversation sucked valuable oxygen away from what we should be concentrating on.
We need to fix our attention squarely on global temperature rise. This is the thing melting the polar ice caps, that will flood heavily populated low lying areas of the planet, causing refugee crises, famine and war; the thing that will cause the extermination of species by the hundreds of thousands. A global temperature rise of just a few degrees.
If we can convince every consumer of the planet's resources to start doing these small, unglamorous things, together we can achieve something huge. But if we expect New Zealand to become carbon neutral, every New Zealand household must be working towards that same goal.
*** One of the problems with changing the equilibrium of any environment, is the law of unintended consequences. As an example, it was once considered a brilliant idea to introduce the Australian Possum to New Zealand so that it could employ people in the fur trade. The result has been the devastation of our native flora and fauna.
Consequences can be equally catastrophic when you ban something. A scientific study undertaken in San Francisco after their ban on single use plastic bags, postulated that an average annual increase in deaths by bacterial infection of 5.5 people per year was attributable to the increased use of reusable grocery bags. (Another study found out why they might be a problem - ninety percent of them never get washed.) This hypothesis, if proven correct, would be a tragic illustration of this.
But even the more mundane consequences of banning plastic bag are not talked about. People must have an alternative, and every alternative has an environmental cost. A non-woven multi-use polypropylene bag weighs 80 grams, an HDPE bag weighs 6 grams. So, if you can get 10 trips from an HDPE bag, you need to get well over 100 trips from a polyprop bag. So if you don't get more than 2 years out of your polyprop bag (assuming approximately one supermarket trip a week), then from an environmental standpoint, you are no better off than if you had been using HDPE bags. But in the meantime, people will still be buying bags for bin liners, dog poo pick up, and every other task for which they repurposed their HDPE bags. So the net result could well be more plastic, not less.
And if you have ever thrown away a multi-use bag because you somehow ended up with too many, rest assured that you are almost certainly not alone. And if it is just now dawning on you that it was made of jute, and you put it in your rubbish bin, so it went to the landfill, where it decomposed anaerobically, which produced methane with a global warming potential of 30 jute bags, then please congratulate yourself, you have obviously been paying attention.