What you need to know
The world is rushing towards embracing bio-plastics because they sound like a nice alternative to banned single-use plastics, but the truth is that in most cases bio-plastics are not biodegradable.
As more cities and countries enact bans on single-use plastics such as straws and bags, the world is rushing to embrace bio-plastics.
Seattle is a standout example. The city's ban on petroleum-based plastics came into force in July, prompting local firms to seek “bio-degradable” plastics, usually created out of polylactic acid (PLA), as an alternative.
But while these seemingly natural plastics do have benefits over conventional ones, they can create complex long-term problems if improperly utilized and cause more damage than their petrochemical counterparts.
Understanding these inconvenient truths is essential if global communities are to avoid further damaging the environment while remaining in thrall to plastics, rather than making the transition to reusable alternatives.
All plastic, at some stage, comes from living material. We extract oil from deposits that millions of years ago were once micro-organisms. Over time, deposition and increasing pressure from accumulating sand, silt, and rock creates what we now call “oil,” thus the term “fossil fuels.” Similarly, coal comes from areas that once held ancient forests.
Creating plastics from recently deceased plant material is essentially as old as petrochemical products. First came latex and natural rubber from rubber trees which Mesoamerican cultures utilized around 1,500 BC.
As for our contemporary conception of bio-plastic, one of the earliest instances was galalith, first manufactured by German chemists using casein (sourced from milk) and formaldehyde in the late 19th century. Subsequently, there wasn’t much development of bio-plastics, as easy to access oil reserves kept the costs of production of conventional plastic low.
A motivational crisis
Then in 1973 and 1979, conflicts in the Middle East ranging from the first oil and energy crisis to the Iranian Revolution, and Iran-Iraq war scared industry enough to start seeking alternatives to oil. Energy independence became a national security goal in the United States, and, pre-natural gas, that development meant substituting oil for other materials such as corn- and soy-based ethanol for gasoline and PLA for plastics.
One of the largest PLA producers in the world, NatureWorks, was set up in 2001 as a joint venture between Cargill and The Dow Chemical Co. This corresponded with favorable corn subsidies in the U.S. and a bio-fuels craze that sought to lower oil imports in the U.S. and make use of surplus corn. However, the growth of bio-fuels was limited by findings indicating it had a larger environmental impact than gasoline. Similar criticisms trailed bio-plastics, and the environmental community did not heavily discuss them in popular media until around 2016, when plastic bans started picking up again.
How it’s made
Bioplastics essentially take cellulose material and process it into a polyester – that’s right PLA is still a plastic. It’s difficult to find a good explanation of PLA that isn’t biased in favor of promoting its use, but this How Stuff Works article doesn’t do a bad job.
The main point is that, when comparing PLA to other plastics, we are essentially comparing the environmental impact of growing plants (fertilizing, watering, and putting pesticides on them, along with the arable land they occupy) with extracting oil (contamination, processing, spills, etc.). Intuitively, we assume that oil is less efficient and more polluting. However, studies have found that animal agriculture exceeded emissions of the largest fossil fuel companies, and by 2050 animal agriculture is on track to account for 80 percent of targeted greenhouse gas emissions.
While corn and other cellulose crops don’t have the same environmental impact as animal agriculture, they still damage ecosystems, generate air pollution, and cause long-term impacts such as dead zones and harmful algae blooms. Corn makes up one-third of U.S. croplands and requires large amounts of water. Moreover, most of it doesn’t even go to human consumption: one-third goes to bio-fuels and another third to animals. Keep this in mind when we start comparing bio and traditional plastics.
Pros and cons
Like bio-fuels and biomass the assumptions that go into environmental impact modeling often determine the final outcome of a lifecycle assessment or LCA, which compares the total impact over a product’s use (from production to disposal). One study in 2013 looked at meta-studies of bio-plastics, primarily PLA, to compare their assumptions.
Often you will find proponents of bio-plastics highlighting two main aspects: lower greenhouse gases and biodegradability. But do these benefits really hold up? When compared with other plastics at a raw material stage PLA does not differ significantly from other types of plastic.
When looking across other areas, mainly eutrophication (the over-enrichment of bodies of water with nutrients leading to excessive growth of plants and algae), ozone depletion, and eco-toxicity, we see an increased impact from PLA. Keep in mind, there was a very large range across all the studies surveyed.
For example, -4 kgCO2 equivalent to 5kgCO2 equivalent is a massive range, one that makes it nearly impossible for a consumer to understand the impacts of a product – depending on which end of the range you favor, the material either reverses climate change or causes it.
In any case, few would spend the time to look through each of these studies. PLA companies take advantage of this by selecting favorable LCAs to use in their promotional marketing.
What leads to these divergent views? Assumptions researchers build into their models. Like biomass, many in the bio-plastics industry assume their product is carbon neutral because they take the carbon of plants and use that to make plastic, that degrades back into CO2 which gets reabsorbed by plants. These companies then claim carbon offsets which drive down the CO2 per kg value. Others use renewable energy during production, and the misleadingly incorporate that as part of the LCA when that is far from the norm for bioplastics.
The theoretical benefits of PLA come from lower emissions during production – it’s generally less toxic than other forms of plastic. They do not require oil as a feedstock, and they can degrade and even be recycled. But does that even happen in reality?
Finally, and most importantly, PLA is not the kind of bio-degradable you might imagine. It’s not the same as a banana peel or an apple core. Products that transport food or need to survive consumer use require additives to make sure they don’t degrade during their usage phase. Those additives are almost the same as the much-feared PET plastic, meaning that PLA is only biodegradable in industrial facilities capable of generating heat of over 130F (54C).
Most places in the world lack the appropriate facilities to break down PLA, and it’s difficult to efficiently break them down in home or traditional composting. They often require either a large-scale row facility or an anaerobic digester to break down. If you toss a “plant cup” on the side of the road, it will lay there for as long as your standard plastic cup.
With more bans on the way, how cities approach bio-plastics will shape our environment and consumption habits profoundly. Aa ban on single-use plastics should thus include PLA because it is not truly biodegradable – though a case could perhaps be made for omission if the proper facilities are locally available to break the material down.
If we somehow had discovered PLA before other types of plastic, our world would look very different. We could develop appropriate industrial supply chains that ensure that bio-plastics end up appropriately recycled, we could utilize the left-over waste for energy, and utilize plant waste as a feedstock eliminating the impact on ecosystems or food production. Sadly, we do not live in that world, and it will take a long time to develop that infrastructure.
As it stands, we need to develop industrial composting to manage municipal food waste and industrial organic waste. Many cities have these systems already, but in Asia, where population and plastic consumption is rising rapidly, nothing comes close.
Imagine the population of India switching to bio-plastic. There will be even greater mountains of un-recyclable, more expensive plastic clogging the streets.
We should design systems that eliminate all forms of disposability rather than replacing plastic with something “better.” Almost nothing can replace plastic in its current form. Redesigning consumption creates new opportunities for economies and sharing, a single-use item will almost never beat reusable item in terms of environmental impact.
It’s also worth pausing to reflect if supporting a type of plastic that the plastic industry also supports is a good idea. Why would they support their own demise? With PLA, none of the plastics or disposable infrastructure needs to change; they simply switch out the plastic and carry on creating mountains of non-recyclable waste.
Still, it’s not all bad. There are companies using algae to make bioplastic and others trying to make PLA out of plant waste, such as 100% Plastic Free which secured headlines in Taiwan for having a bio-degradable plant straw. Unfortunately, upon closer inspection, the producers reveal that the straws are made of PLA and that Taiwan has no way to recycle or compost this material. While it’s good progress to use waste material, this company is taking a naturally biodegradable substance, sugar cane, and making it into a plastic which cannot naturally degrade.
Overall, PLA and bio-plastics are complex and location dependent. To determine if it’s right for you or your business look up your local waste collector and see if they accept PLA, usually in a yard waste or composting bin. Until we find suitable ways to dispose of and process PLA, it’s generally best to avoid both for cost and green-washing reasons.
However, I for one look forward to a future in which this article is outdated as we have the kind of circular consumption systems that make discussions of single-use materials redundant.
Editor David Green (@DavidPeterGreen)
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