We have all now become more aware of the damage that plastic can cause to our environment. We produce an incredible 348 million tonnes of plastic8 globally every year. And around 10 percent of the plastic we produce ends up in our oceans. However, science and innovation now present us with the choice to replace standard plastic bags with either degradable or biodegradable variants. Hence, let's take a look a look at what the difference is between degradable and biodegradable plastic bags? And are they really better for the environment?
The Problem With Regular Plastic Bags
Plastic waste is a problem that we all have to deal with. Reducing the amount of plastic we use should be a high priority. For decades we have been using traditional plastic bags. We've used them in our waste bins as bin liners. We've used them to throw away food waste, and we use them to carry our shopping. We can find them almost anywhere.
Our reliance on plastic bags cannot go unnoticed. They have become a part of everyday modern life for many of us.
However, much of the plastic problem comes from treating plastic bags as one-use items. We would use them and throw them away with little care or thought for our environment.
Did you know that single-use plastic bags have a useful lifespan of 12 minutes on average? I.e., the average time we actually use them to carry our groceries or shopping before they get discarded.
And we get through a lot of plastic bags. In the UK, before the plastic bag charge, each of us used to get through 140 single-use plastic bags a year on average. Globally, it's said we consume more than one trillion plastic bags a year9. That's about one million of them every minute.
The Plastic Bag Problem
Made from polyethylene, regular plastic bags come from non-renewable petroleum-based sources. And that would be all very well if we weren't faced with the problem of how they decompose once disposed of2. In fact, the problem is more about how they don't decompose.
Standard plastic takes hundreds of years to decompose6. So from the Ocean to landfills, the plastic we use will still be decomposing way beyond our lifetime. When it does break down, a plastic bag breaks down into tiny pieces, which can affect the broader environmental ecosystem.
Once the plastic has broken down into small particles, called microplastics, they leach into our waterways or oceans. Once there, marine animals can consume them. As such, plastic can enter the food chain. And it is washing up on shorelines across the globe7.
The plastic problem we face is vast, but can we make a difference by switching to biodegradable or degradable bags?
Degradable Plastic Bags
If something is degradable, it means that large molecules can break down into smaller fragments3. Degradable plastics are still commonly petroleum-based, yet with chemical additives included to help speed up the degradation rate. However, degradation remains a problem for the environment.
The word degrades means "to break down" and essentially, all plastic is degradable. It can either be broken up by hand or machinery in large recycling or processing plants. Or it can go through the natural process, which can take thousands of years. A plastic bag labeled degradable won't have an official time stamp indicating how long it takes to break down. It will take as long as it needs to take.
This might leave you wondering whether degradable plastic is a feasible alternative to traditional plastic bags?
The reality is that experts say that degradable plastic bags are not as eco-friendly as we might have thought4. Simply because the natural environment rarely presents the conditions required for these plastic bags to break down optimally.
The way to look at this is that degradable bags do not return to the earth's organic matter. Instead, they still return plastic particles, just faster. This means that we still face difficulties in removing the resulting degradation from the environment. And that degradation remains plastic.
Biodegradable Plastic Bags
On the other hand, biodegradable plastic bags work differently than degradable bags. They make shopping bags and biodegradable garbage bags using renewable materials such as plant starches, micro-organisms, or petrochemicals. In fact often a blend of all three. As such, they usually contain less petroleum-based plastic, which is good news.
Manufacturers adapt the composition of biodegradable plastic bags to also break down at a faster rate. And into less harmful particles due to their composition when exposed to natural elements.
Primarily they design biodegradable bags to break down when exposed to micro-organisms such as bacteria, fungi, or algae. The resulting degradation problem can remain if they still contain petrochemical plastics, albeit less so.
Indeed, one benefit comes as more and more biodegradable bags get made from plant-based biodegradable materials. This can include the likes of corn starch or wheat starch. And results in an improvement over petrochemical-based plastic. Coming from a higher proportion of natural sources reduces their chances of ultimately becoming nasty plastic pollutants.
Conditions for Degradation
However, they also require specific conditions for most of these bags actually to break down1. Usually, the temperature has to reach 50 degrees, and there needs to be the correct amount of UV light5. So, the conditions may not be right for plastic waste that finds its way into the Ocean.
Also, once in landfills, they break down without oxygen. This can then lead to the production of methane, a greenhouse gas, which is more harmful to the environment than carbon dioxide. In this case, this renders them no better than traditional bags.
All the same, biodegradable polymer research marches on at a pace while science grapples with aiding our plastic pollution problem. Researchers make advances all the time, resulting in new innovations that improve the biodegradable qualities of new plastics. Many have not yet made the mainstream but may well do so.
As a general rule, when buying biodegradable products look for a composition containing as high a proportion of plant-based and organic materials as possible. Compostable is almost always the best choice. Compostable plastic bags will break down more naturally in landfills and water in more natural conditions where moisture and warmth are present.
Is One Better than the Other?
It is clear to see that there are differences between the two. A degradable bag will take longer to break down; it can still take hundreds of years. Even then, tiny pieces of plastic will still remain.
A biodegradable bag breaks down at a different rate. It relies on micro-organisms to speed up the process, and that sounds like a good thing, but is it?
Whether degradable or biodegradable, these new plastic bag variants cannot be easily recycled. And there are inevitably still by-products left behind after their different degradation speeds. People might think that biodegradable means that it will disappear. They might also believe that it is good for the environment. Unfortunately, neither are absolutely true.
Also, while they present advances and improvements, neither help to deal with the consumption problem. If there is a belief that biodegradable is better, then it could add to the problem.
So, in our quest to reduce plastic waste, we should be moving away from plastic bags altogether. You can undertake a range of simple steps to reduce your plastic bags use, from composting food scraps and other compostable materials,
Of course, we can use plastic bags by reusing them; however, there are also compostable, plastic-free, zero-waste alternatives. You can even find a growing range of compostable poop bags for pet walks.
With the likes of compostable bags and bags made from wholly natural materials, we have a choice. We need to think a little differently and make better decisions.
|F.-D. Kopinke, M. Remmler, K. Mackenzie, M. Möder, O. Wachsen, Thermal decomposition of biodegradable polyesters—II. Poly(lactic acid), Polymer Degradation and Stability, Volume 53, Issue 3, 1996, Pages 329-342, ISSN 0141-3910, https://doi.org/10.1016/0141- 3910(96)00102-4
|H Bockhorn, A Hornung, U Hornung, Mechanisms and kinetics of thermal decomposition of plastics from isothermal and dynamic measurements, Journal of Analytical and Applied Pyrolysis, Volume 50, Issue 2, 1999, Pages 77-101, ISSN 0165-2370, https://doi.org/10.1016/S0165-2370(99)00026-1
|R. Mohee, G.D. Unmar, A. Mudhoo, P. Khadoo, Biodegradability of biodegradable/degradable plastic materials under aerobic and anaerobic conditions, Waste Management, Volume 28, Issue 9, 2008, Pages 1624-1629, ISSN 0956-053X, https://doi.org/10.1016/j.wasman.2007.07.003
|Plastics of the Future? The Impact of Biodegradable Polymers on the Environment and on Society. Tobias P. Haider Dr. Carolin Völker Dr. Johanna Kramm Prof. Dr. Katharina Landfester Dr. Frederik R. Wurm. First published: 04 July 2018. https://doi.org/10.1002/anie.201805766
|Plastics of the Future? The Impact of Biodegradable Polymers on the Environment and on Society. T. P. Haider, C. Völker, J. Kramm, K. Landfester, F. R. Wurm, Angew. Chem. Int. Ed. 2019, 58, 50.
|Decomposition and analysis of refractory oceanic suspended materials. D. W. Eggimann and P. R. Betzer. Analytical Chemistry 1976 48 (6), 886-890. DOI: 10.1021/ac60370a005
|Invasions by marine life on plastic debris. David K.A. Barnes. Naturevolume 416, pages 808–809 (2002). https://doi.org/10.1038/416808a
|Plastics - The Facts 2018. PlasticsEurope. Association of Plastics Manufacturers
|Plastic Bag Fact Sheet. Earth Policy Institute.