Polyvinyl alcohol (PVOH, sometimes also called PVA) is a synthetic polymer and plastic that is water soluble and biodegradable under both aerobic and anaerobic conditions. Without much fanfare, in recent years, PVOH has started to be used as a packaging material and in other single-use products: laundry detergent pods, for example, where the entire pod is placed in the washing machine, are made of PVOH. In use, the PVOH film dissolves, releasing the detergent into the laundry at the correct point in the cycle.
That seems pretty clever from the perspective of user convenience, and also from a waste prevention point of view – it avoids the need for detergents to be packaged in plastic bottles, and material that dissolves doesn’t end up in the bin. PVOH being characterised as “biodegradable” has also made it an increasingly popular choice for eco-cleaning products. But does its performance in practice justify its reputation as an eco-solution?
A number of eco-cleaning brands mention their use of PVOH to bolster their environmental credentials, seeking to reassure customers about their commitment to reducing plastics. On the OceanSaver pods website, for example, the top FAQ avoids mentioning that PVOH is a plastic at all:
It would be easy for someone to read this answer and come away without understanding that PVOH is a plastic. To be fair, Oceansaver is more candid about their approach to plastics in another answer:
But the claim that PVOH is “fully, and easily biodegradable in the environment” is one we’ll come back to, as matters aren’t quite so straightforward.
Tru Earth uses PVOH as a structure matrix to create their laundry strips, but one of the headlines on their website says “Plastic-free, Zero Waste Laundry Detergent”. You have to read on to learn that they are referring to their product obviating the need for plastic laundry jugs, and that there is no plastic in their packaging (which they say is plastic-free, compostable cardboard). Consequently, a superficial reading of the marketing material might leave the impression that the product is plastic free, but they never actually make this claim.
The two main claims that are being made about PVOH are that it is water soluble and biodegradable; i.e. first the pod or strip dissolves in water, and then it biodegrades. Is this an eco-friendly approach?
So, first the plastic film dissolves in water. To dissolve means to become incorporated into a liquid, so as to form a solution. It does not mean that the molecules themselves break down or degrade. In other words, it just means that plastic film breaks down and the little PVOH molecules that made up the film now float around in water. Little bits of plastic loose in the environment seems to be exactly the definition of a microplastic! However, if they biodegrade before they can do any harm, maybe that isn’t so bad.
Biodegradation is, very simply, degradation of a material caused by biological activity, or in the words of the Oxford English Dictionary, a biodegradable substance is one “capable of being decomposed by bacteria or other living organisms and thereby avoiding pollution.”
This can be tested in a lab: put a sample of your material in a box with some microorganisms and oxygen, and measure the growth of the microorganism, the reduction in oxygen, and the increase in carbon dioxide that the microorganisms produce. There are a number of different test standards that can be applied: for example, the Tru Earth laundry strips are certified to be biodegradable in accordance with the OECD 310D methodology.
However, a 2009 study showed that, when tested against the Chinese national standard, pure PVOH takes over 32 years to biodegrade. This is obviously quicker than the hundreds of years you often see quoted for other types of plastic, but is hard to square with the OceanSaver FAQs claim that their product is “easily biodegradable”. A recent Eunomia report on the definition of plastic in EU legislation explains that it is difficult for a lab test to replicate how biodegradation will actually occur in real life. As the report notes, “This is particularly challenging given the diverse conditions and biology of the marine environment.” Quite a battery of tests would be needed to demonstrate that a polymer is capable of biodegradation under some of the cold, low-oxygen conditions that can be found in the oceans.
PVOH is one of the many plastics found in seafloor micro-litter and unidentified polyvinyls closely resembling polyvinyl alcohol or polyvinylchloride have been found in the stomachs of fish 10km below the ocean surface. This suggests that the claims made for PVOH’s biodegradability don’t seem to reflect its real-world performance.
In addition, although PVOH is claimed to be nontoxic, it has been found to produce foam as it degrades, which prevents the recovery of oxygen in the water. This causes a serious threat to water-borne organisms, and also some degree of risk to humans.
One way to think about the level of usage of PVOH that could be environmentally sustainable is that its rate of release into the environment can be no greater than the rate at which it can be degraded. But how do we know what that rate is? Are we already releasing too much into the environment? It is important to consider this issue at a local, rather than a global level, in order to avoid exceeding the capacity of any one area to degrade the material and avoid the build-up of potentially harmful levels of the substance.
Laying off the bottle
Despite the environmental risks of using PVOH in laundry pods and other cleaning products, their waste prevention benefits seem undeniable. Take OceanSavers, for example. They offer soluble pods of concentrate that you dilute at home to make up your own bottle of cleaning product, and the pod helps ensure that you get the concentration of the liquid right. The OceanSaver homepage features a counter showing the number of plastic bottles saved as a result of customers using their products, which at the time of writing is approaching 700,000.
I weighed an empty spray bottle recently, and recorded a measurement of 50g, which implies that OceanSaver has prevented nearly 35 tonnes of plastic bottles from arising. I’m not sure how much PVOH is in 610,496 cleaning pods, but it’s definitely much less than this. However, by design PVOH products are washed straight down the drain, into our waterways, via sewage treatment that isn’t designed to capture microplastics. Most of the pod material will therefore end up in the environment. In contrast, most plastic bottles will be captured in waste management systems with only a very small percentage escaping into the environment. Is using less plastic in a product necessarily better in this case?
Many of the eco-products mentioned above trade on the idea that most of what we are buying in our cleaning sprays and detergent bottles is water: a typical bottle of cleaning product is 90% water. Concentrating the active ingredients into a pod or strip avoids the need to package and transport most of the content of a normal, pre-diluted product.
But similar benefits can be obtained in ways that may prove to be more environmentally friendly than cleaning pods, such as concentrated cleaning products and bulk refills. Measurements I’ve taken indicate that using a 5-litre jug of washing up liquid to refill a smaller bottle in the kitchen uses 40% less plastic than buying a new bottle every time, and that’s assuming the bulk jug isn’t concentrated.
A one litre bottle of concentrated multi-surface cleaner can refill a 500 ml spray bottle 167 times (if measured out correctly), which saves 8 kg of plastic spray bottles from arising! And assuming it is properly recycled, this approach releases no microplastics into the environment.
If we’re to decide whether PVOH products are an eco-solution, we need to determine the balance between some quite difficult to compare environmental considerations. Are savings in transport emissions and packaging production that PVOH offers worth releasing additional microplastics into the environment? How quick and complete would PVOH’s biodegradation need to be to reduce concerns about microplastic release? How good is the performance of the plastic recycling system for cleaning product containers? And what are the prospects of getting people to make more use of refills and concentrates?
These are not questions that can be answered based simply on theory, and the answers may differ depending on where the product is used. For example, where waste management is poor, PVOH may seem like a better option than where recycling performs well. It would be good to see PVOH products subject to much closer life cycle analysis to help inform consumers who want to make eco-friendly choices.
Featured image: Maxine von Eye via Instagram (@maxiandjoe1)