What began as two graduate students exploring the usage and degradation of laundry and dish detergent pods, has now turned into an effort to ban these popular consumer products. How did we get here?
The pods are coated by a unique plastic polymer, called polyvinyl alcohol (PVA). What makes it unique is how it feels and what it does once it interacts with water. The plastic itself is what we call “hydrolzyed”, meaning water can disassemble the plastic coating, releasing the detergent into water. The concern begins when we ask what happens to that plastic coating. It’s water soluble, just like sugar or salt, which once added to water, disappears in time, but as we can taste, still very much remains within the water itself.
This concept of out of sight, out of mind has led many to believe that PVA is biodegradable. Couple that with the fact that the EPA designates polyvinyl alcohol to be of, “low concern based on experimental and modeled data”, data we have never been provided, and now companies have gone to lengths to say that the pods are “ecofriendly”, “biodegradable”, and even “plastic free”. Are these true? Mostly, no.
When water leaves your house after a wash, for those of you in bigger cities, it will travel to a wastewater treatment plant. These plants are built to remove smells, pathogens, and more, to either create a very rich fertilizer for crops, called biosolids, that can also be landfilled, or incineration. Regardless, it’s meant to be safe. One of the major aspects of the wastewater treatment process relies on microorganisms within the plant attacking the solids, thus lowering their volume, and adding to the nutrients of the solids.
Polyvinyl alcohol was used often as a binder in the textile industry. These textile plants would put out so much of the material in their wastewater that the microorganisms in the wastewater treatment plants downstream became adapted to them and could break down the material very efficiently. This helps give us insight into what conditions can make polyvinyl alcohol actually biodegradable, but more importantly, we’re able to learn why it isn’t biodegradable in most of the US or around the world.
Certain conditions are necessary for hydrolyzed polyvinyl alcohol to biodegrade, as demonstrated by copious amounts of scientific research. Not only are specific microorganisms needed that have been adapted to the material, but the amount of time they spend with it, as well as the correct temperature and pH are essential as well. For example, studies show that if the correct microorganisms are exposed to PVA for up to 60 hours, a significant amount of degradation can be seen. The problem is water stays within conventional wastewater treatment plants for hours to a few days, at most. There are also varying temperatures and pH levels in these treatment plants as well, making biodegradation that much more difficult.
The research I conducted with Varun Kelkar, with support from Blueland, aimed to gather all the papers looking at PVA degradation within these treatment plants. We found that only about 25% of the material breaks down, with 75% passing through into ecosystems beyond. This leads to an estimated 8,000 metric tons of PVA surviving the wastewater treatment process. To give you an idea as to how much that is, an elephant or great white shark weigh roughly one metric ton.
So how does PVA behave as a pollutant? Is it like other conventional plastics that can adsorb dangerous chemicals, get stuck in tissues/organs, or travel the heights and depths of the planet? We don’t know, but we’re working on it.
We’re currently collaborating with the University of Maine and others to better understand how PVA acts as a pollutant. Until there is more certainty, cities like NYC are more comfortable banning the use of the pods. You might be thinking, “well, these pods have to be better than the plastic jugs, right?”. Eh. Plastic jugs have a chance at getting recycled, and if they aren’t, they’re most likely heading to a landfill. These pods become a plastic solution instantly after use and reach the environment much more quickly, in hours or days. Think of them like the plastic microbeads that President Obama banned in 2015.
I never try to poopoo something new too quickly. Maybe these pods can be transitioned into being made from a material that is natural, like seaweed. There are rumblings of this occurring. Until then, there needs to be better truth in labeling, more research on PVA as a pollutant, and transparency for consumers.
