Compostable Plastics: Safety Net or Dangerous Distraction?

There has rightly been a huge focus on compostible plastics over recent years. PLA in particular has risen as a major form of bioplastic made out of potato starch. Yet, if not handled correctly, bio plastics can easily be as bad as petrol plastics for the environment. Infecting ecosystems and making their way into food chains in exactly the same way as every other petroplastic out there.

Not only that. While PLA is "compostable" in the technical sense of the word, it requires industrial composting facilities and don't biodegrade in home composting bins. This means they need municipal waste facilities with appropriate agents and piles in very warm, humidity controlled conditions for them to actually compost. A home composting bin simply can't reach that standard.

Worse still is the effect of misclassification. While PLA doesn't degrade in home composting, it does in landfill! Worse, it emits methane when it does it. The dangers present within landfills, especially given the risk of ignition of that methane from those bioplastics, risks fire and the emission of even worse greenhouse gases than carbon dioxide.

Methane alone is 28 to 36 times worse than CO2 over 100 years. If piles combust, they release 44kg of CO2 for every 16kg of methane that burns. Making them particularly unsuitable for final incineration for energy as well, even though that has less GWP. Especially where no carbon capture takes place. We need to solve that and some solutions to this problem already exist.

However, the carbon dioxide emissions of all plastics are skewed to the embodied carbon in the processing, production, freight, transportation, storage and disposal of all these plastic items that isn't the product itself. Scope 3 emissions for those familiar with the Greenhouse Gas Protocol. It can be upwards of 90% of the emissions of some production, including textiles.

That carbon dioxide can be between two and 10 times the weight of the plastic item and while these potato starch based plastics only require 30% of the energy of petroplastics to make in the first place, they are subject to exactly the same embodied carbon footprints as any other plastic in transportation and disposal.

While it is great that different research groups are examining truly compostable plastics (as we are - together with edible plastics), it is important to realise an earth-to-earth strategy Does little to remove this embodied carbon footprint. Indeed, if the process of creating a composable plastic increases the energy required to process the raw materials and turn it from its constituent parts into a usable plastic, then this has the effect of increasing the carbon footprint associated with plastics, which emits more greenhouse gases and burns down the houses of land mammals and acidifies the oceans of marine life, even if it claims to prevent damage to biodiversity through the front door by simply degrading before it gets there.

There is a silver lining though. Almost all compostible plastics in existence today, are also entirely recyclable.?They also recycle many more times than petroplastics.

But why recycle bioplastics/compostable plastics? Here are 5 reasons, which will change in time.

1. Lower emissions

Because recycling cuts out a large portion of the greater circular chain, it means the energy required to recycle plastics is significantly less than creating plastics from scratch, including the latest truly compostable hard plastics. Typically, recycling uses less than 1/4 of the energy required to process new plastics, and if it is done locally it is also removing the freights miles from transportation from manufacturers in places like China or India through to the UK. In total it is 60% less emissive of CO2 than new plastics and that’s almost double what truly compostable plastics save in landfill or compost piles

For example, if you have a compostible plastic that has an energy footprint similar to bioplastics (which are themselves 30% of petroplastics), the emissions of freight storage and disposal are identical to petroplastic when landfilled, not incinerated. Which in turn, means that 30% only makes a material difference of 9% of the full carbon footprint of items. If you made them locally, from recycled existing plastic material (instead of shipping or burning them) you reduce the amount of plastic in the environment and also save more than 70% of the carbon footprint from the embodied chain. Overall, this means that recycling existing petrol plastics is better than waiting for and then could you sing compostible plastic alternatives in remote facilities. This is almost eight times greater reduction than truly compostible plastics could ever give you on their own.

2. Efficacy

Focusing only on compostable plastics without looking at the supply chain as a whole, risks negating the potential of newer compostable plastics by offsetting that effect downstream, or into the next cycle.

In addition, it still leaves us with the problem of what we do with the plastics that are in the environment at the moment. Since plastics last for 450 years, the GPGP won't clean itself up.

Politically, there is always the risk that the existence of composable plastics simply overshadows the current plastic dumping problems because governments and societies may simply forget about the intricacies of the problem. Just like our systems create the opportunity for a different form of wishcycling.?

3. Cost

At the moment, creating truly compostable plastics isn't in the mainstream, but it will eventually be. It is important to consider what to do in the meantime, given every new plastic we create adds climate harm. Hopefully it gets to the point of being as cheap as current petro or bioplastics, but if it doesn't, then this creates an inequality that widens the climate inequity between the global North and South. a direct violation of SDG 10.

4. Source

Some of the compostable plastics that are currently being considered actually come from animal sources. Fish scales in particular have been used to make soft plastic systems. We already have enough material to plastic it out of waste, so it raises the question of the need to cause extra harm to animals.?

5. Health Outcomes

The UK, as with many parts of the world, has a carbon footprint including 6 and 10% from its healthcare system. As established, creating compostable plastics and still using the same freight mechanisms, create air quality issues that then exacerbates the amounts of carbon dioxide that care services provide. The reason for this is because of the much higher global warming potential of the gases used as propellants within inhalers and even in anaesthesia. This is an area where climate activism has unfortunately caused a different problem to the one it intended to solve by removing CFCs in the 1980s. HFA’s have a 500 times higher carbon footprint than CO2. Anaestheics have up to 11,000 times the Global Warming Potential of CO2. These are figures so high, they create their own demand on the service, like London has it’s own microclimate.?

Every 77,100 cases of acute asthma requiring hospitalisation create 64 new cases of asthma every year just by inhaler treatments. This in turn, creates more single use plastic consumption.?

Inconvenient Science

This is why it’s important to think about conventional plastics as part of a very wide supply chain from oil, or crop waste, all the way to use and disposal. Plastic doesn't appear by itself after all. Each plastic item, from whatever material, has a carbon footprint that is more than twice the footprint of the weight of plastic material itself. This leads to a very inconvenient set of truths that we have to become comfortable with if we are to act correctly solve the climate crisis.?

1. Anytime you take something on the full journey from from soil-to-soil, what you then need to do, is recreate the future item from soil again. Which means accumulating all of the footprint required to make that plastic from scratch. Compostable or not.

2. Every time you recycle instead of dispose, the effect is to remove the need to do the same long cycle again.?

3. We need to use materials by longevity. "Single use" plastic use-cases should never exist or ever have existed, as the material lasts 450 years or more. There are plenty of cases where mycelium could be used instead (mushrooms).

All things considered, this sadly means plastics should never make their way back into the soil again.?Whether to compost or not. However, we live in the real world and mistakes happen. So having a truly compostable plastic prevents the damage that would occur of it made its way there. The question is whether shifting the whole country to compostable hard plastics, to trade off against mistakes, is a good idea? Trading certainty for uncertainly rarely is. Equally, if compostable plastics don't create downstream footprints and are made equally as recyclable, it's a no brainer to use them! This is why we are keenly exploring them as part of our innovation pipeline. What we certainly know, it's not a "get out of jail free" card.