Compostable Plastic: A Breakdown

You may have heard lots about plastic in the past year and you may be sick of it, but the fact is plastic is still a problem and will be until we all take it seriously. Taking it seriously for me means looking at how I use plastic in everyday life and being mindful of how much I discard; that odd bit of clingfilm covering last night’s leftovers in the fridge, the packaging that my bamboo toothbrush arrived in, the blister pack containing my vitamin D tablets and a Kinder Egg toy to name just a few. None of these items could be recycled and will join the 5.7 billion tons of plastic that has been wasted in the 60 years that plastic has been produced.

On a global scale, the world produces around 300 million tons of plastic every year (the mass of about 43 million African elephants). Approximately 8 million tons (1 million African elephants) of this ends up in the ocean where it is brought to our attention by Sir David Attenborough.

With all the recycling that we do, you might wonder, surely this wastefulness is decreasing and yes it is, but recycling is not the only answer. As the picture below shows, not all plastics are recyclable. In fact, only 2 out of the 7 common types of plastic are ‘widely recycled’ which means that since the dawn of plastics, only 20% of discarded plastics have been recycled! The other 80% has either gone into landfill or been incinerated, both contributing their own types of pollution into the pollution soup swirling above our heads.

Similar to paper and cardboard that was discussed in my previous article, plastic can only be recycled a limited number of times (two or three) before its structure becomes too weak to be useful.

Source: ourworldindata.org

A Silver Lining

It’s not like me to be all doom and gloom, so I want to share a shred of light pushing through the mound of plastic we’re buried under.

After purchasing food from an outdoor food kiosk at the end of summer, I was presented with what I thought was a plastic fork to eat my lunch with. I was wrong; on closer inspection the fork had the word ‘compostable’ pressed into its handle. After finishing my food and taking the fork home (as you do), I hesitated before putting this supposedly compostable piece of cutlery into the food bin where I assumed it belonged. Instead, I put it in the cutlery drawer, unsure how to proceed with what felt like a hard plastic fork.

Later, at the beginning of this year, I purchased a fruit salad packaged in a plastic pot. I was disappointed at this because the shop was supposed to be promoting sustainability, but my frown was turned upside down when I saw the words ‘Vegware – fully compostable’ moulded into the lid and thus began my research into biodegradable plastics.

Typically, the average plastic bottle takes 450 years to biodegrade and even then it can result in the formation of microplastics; a hot topic at the moment. Vegware claims to go from packaging to ‘high grade compost’ in just under 12 weeks in commercial composting. Their selling point is that you can simply discard soiled food containers into the food waste bin instead of having to wash them out and put them in the recycling bin.

Secret recipe

Thankfully the recipe for this compostable plastic is widely available to anyone who wants to learn about it! The material these food containers are made from doesn’t contain an ounce of plastic; the only ingredient is Polylactic acid (PLA).

I’ll start at the beginning of the bioplastic life cycle with a greenhouse gas that is abundant in the Earth’s atmosphere: carbon dioxide. Plants use a process called photosynthesis to convert carbon dioxide to carbohydrates such as starch which are essentially long chains of sugar molecules known as glucose. The most common plant used for bioplastics is corn which stores a lot of carbohydrate during its life swaying in a field.

Corn is also widely used for animal feed and so you may think that this is anothe incident, similar to biofuels, where the an eco industry and hungry humans are fighting for the same material. Luckily this is not the case; the bioplastic process uses a type of corn called #2 yellow dent field corn. This is used only to feed animals and for industry. Animals only need the protein extract whereas bioplastics use the starch which would otherwise have been discarded as a waste product. More information about the sustainability of growing #2 yellow dent field corn can be found on the Nature Works website.

After harvesting, the corn is milled and glucose extracted. The glucose is then further broken down before being fermented by microorganisms to produce lactic acid. Lactic acid molecules are then formed into rings which are joined together to form polylactic acid- a easier way of saying ‘many lactic acid molecules glued together.’

PLA is then formed into pellets which can be used in a variety of different ways to produce many different bioplastic products including sandwich box windows, cutlery, and portion pots.

How does it compost?

PLA in Vegware is designed to be compostable which is quite different to biodegradable. Both are a process of breaking down something big into smaller things but biodegradation can happen with and without oxygen in any given time frame with the help of microorganisms.

Composting happens under very specific conditions and in a given, often smaller, time frame compared to biodegradation. The process requires warmth, oxygen, microbes and moisture and there are strict rules as to the amount of time it takes for something to breakdown and decide whether it can be labelled ‘compostable.’

Compostable doesn’t mean simply throwing a bit of soil on your used bioplastic fork. Industrial composters, such as those used to break down food waste collected in some UK counties, are specially managed to make sure conditions are perfect for quick breakdown of waste into nutrient rich soil that can be safely used in the environment. Vegware does say that putting their products in personal compost bins does is allowed but rates of breakdown can vary depending on the uncontrolled conditions of these bins.

A Cure- All?

Carbon- neutral, compostable and sturdy. The description makes it sound as if bioplastics will cure all the ails that conventional plastic has inflicted on our planet.

Not quite.

Bioplastics have to be disposed of in the right way, as mentioned above, to allow them to complete their life cycle and have no or very little environmental impact. It’s inevitable, however, that some of these bioplastic products will end up in landfill, incineration or the ocean.

In terms of landfill, the main concern for waste is the huge amounts of methane that these sites produce, although, a well managed landfill site will have controlled conditions in the pits and collect the methane given off from the waste. Luckily for bioplastics, they don’t produce any methane when they end up in landfill, but they don’t break down very easily either. The conditions in landfill simply don’t match those needed for effective composting so they are likely to persist for a long time, albeit not as long as conventional plastic.

When incinerated, bioplastcis don’t give off any harmful gases and actually produce more energy than paper, wood or food waste which could be a good thing but as we’ve seen with fossil fuels, burning things isn’t always a good idea!

Similar to landfill, the oceans also don’t provide the conditions needed to breakdown bioplastcis and Vegware states that their products are not a solution marine plastic pollution. Their message is that people need to take responsibility and make an effort to dispose of bioplastics in the correct way- they even offer a collection service for vegware products to make it easier for businesses to dispose of it.

As it turns out, composting could be cheaper than landfill because of the increase in taxes on landfill waste that began in April 2011.

Other uses for PLA and CPLA

You’ll be pleased to hear that bioplastics are being used in more than just the food and drink industry! Nature Works, a key manufacturer of PLA, gives many examples of how its bioplastic branded ‘Ingeo’ can be used. Clothing, toys, electronics and building materials are only a few of the things that they list which is very exciting and shows that bioplastics can realistically provide an alternative to plastic.

Some questions still remain: can production meet demand if everything that is currently made out of plastic suddenly switched to being made out of a bioplastic? Would people commit to the proper disposal of bioplastics? Would people continue to think about how to clean up the mess of conventional plastic that is still out there?

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