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Plastic | Recycling

Recyclable, compostable, biodegradable plastics – what does it all mean?

When you think about it, plastic is probably the best thing that humans have ever invented (the material of a thousand uses) but now we have discovered that it is also the worst thing we have ever invented. The world has produced 8bn tonnes of plastic since the 1950s and none of it has disappeared unless we have burnt or recycled it.

We manufactured 300 million tonnes of plastic last year and this is expected to rise by 4% this year. The UK alone uses over 5 million tonnes of that total each year. And we’re making most of it from oil—a non-renewable resource that’s becoming increasingly expensive. It’s been estimated that 200,000 barrels of oil are used each day to make plastic packaging for the United States alone.

We are still speculating how long it takes plastic to completely break down, maybe 500 years, maybe 1,000 years no one knows, but what we do know for sure is that plastic is polluting every part of our planet and virtually every organism on it including us.

Its effects differ according to the size and state of the plastic – but basically macro-plastics (large pieces of plastic) are ingested, mistaken for food by mammals, fish and birds. This ingested plastic remains in the stomach and can lead to starvation of the animal, alternatively large pieces of plastic can entangle organisms leading to a slow lingering death.

Smaller pieces of plastic such as Microbeads affect organisms lower down the food chain. Small fish may mistake the particles for planktonic food and eat them. Once again they may die of starvation.

At the bottom end of the food chain we find plankton and filter feeders. These organisms are most vulnerable to pollution from tiny plastic particles including micro-plastic fibres. They ingest the fibres which can lead to blockages and death.

We can understand the effects of plastics at a visible level but there is another problem that may be even more dangerous to all organisms. Toxins from all these plastics accumulate in animal tissues and these toxins increase in concentration as food moves up the food chain. By the time they reach us they can be quite harmful, although we do not yet know the full extent of their effects we already know it is not good!!

Now that we have woken up to the dangers of the plastic mountain what can we do? Firstly we can reduce our usage, recycle more and reuse as much as possible, alternatively we can replace plastic with other materials.

Programmes such as Blue Planet II have awoken the sleeping giant of man’s innovation. Many of the largest plastic manufacturers are developing and starting to produce biodegradable plastics, compostable plastics and more useful recyclable plastics. The concepts are sound but, as with so many of these quick fix ideas it is by no means sorted.

Not only are the new materials more expensive but terms such as biodegradable can be deceiving, as we shall see later.

Let us have a closer look at each of these ideas in more depth –

Recyclable plastics

Plastic is a valuable and finite resource and environmentally the optimum use for most plastic after its first use, is to be recycled – preferably into a product that can be recycled again. There is a wide range of markets for plastic ready and waiting both in the UK and overseas and we need to marry the two to make sure more of our waste plastic is recycled.

Statistics from WRAP (Waste & resources action programme) indicate that recycling plastic into end applications that displace virgin plastics can save on average two tonnes of CO₂ for every tonne of plastic recycled. The more we look at recycling the more it appears to be a no brainer and yet we are still dumping millions of tonnes of this incredible material into our environment.

One drawback is that recycled plastic is generally not used to make the same items the next time around: old recycled plastic bottles don’t usually go to make new plastic bottles, but to make lower-grade items such as plastic benches and fence posts. Still beneficial but it also means that we still need some virgin plastic materials.

However recycling plastic means that the requirement for prime virgin material is lower and in products that use recycled plastic it acts as an alternative material.
Many councils in UK claim to recycle 44% of the plastic recovered through waste systems, the real figure is probably nearer 12%, but how can there be such a discrepancy. Previously they have sold much of the waste plastic to other countries such as China under the impression that it is being recycled. It turns out that the waste sent is often contaminated or poor quality and most of it is dumped or burned, which scuppers our figures.

Now we have another problem, in 2017 China refused to take any more of our waste so we have to find another country to sort our waste, do it ourselves, dump it or burn it. At present we do not have enough recycling facilities in UK to cope with the huge tonnage of waste plastic produced annually so we are in a bit of a fix.

We also have another dilemma in UK, around 1 in 10 are confused about plastic recycling. There are so many types of plastic, some of which are recyclable, some of which are not that people become confused. We either end up dumping plastic in the landfill bin or putting the wrong stuff in the recycling bin. This makes it difficult for our councils to separate the good stuff from the bad and reduces our chances of recycling. We need more uniformity and better labelling to increase the percentage recycled. WRAP are coming up with good ideas but this will take a long time to filter through to the general public.

Biodegradable plastics

In the past if I saw the word bio-degradable I thought that’s good, that product is environmentally friendly and breaks down into harmless compounds, but now, with more knowledge I realise it does not necessarily mean that at all. The words photodegradable, oxydegradable or just biodegradable seen on plastic bags or packaging, means they contain additives that cause the plastic to decay more rapidly in the presence of light and oxygen (along with the help of moisture and heat). However unlike compostable plastics, biodegradable plastics are usually still made of petrochemicals, they may break down into smaller pieces of plastic more rapidly but they still leave most of the plastic and possibly other dangerous toxins such as cadmium, lead and beryllium as well.

Another harmful side effect occurs if biodegradable plastic is dumped into landfill, it can produce Methane. This is another of the greenhouse gases but 25x more potent than CO₂ in causing global warming. The fact that Methane is energy rich means that in many parts of the world such as USA it is now captured and used as an alternative energy source, but this does not detract from the fact that biodegradable plastics producing methane are harmful for the environment.

We must also bear in mind that if we mix biodegradable plastic with recyclable plastic it renders the recyclable plastic useless, and the whole batch will end up in landfill or burnt.

The upshot is that biodegradable plastic can actually have the opposite effect of what the name implies, we are more likely to use it and discard it into the environment thinking that it is not causing any harm. It sits between compostable plastic and conventional oil based plastic and is more a source of confusion than a solution.

Compostable plastics

The theory behind compostable plastics is good and simple: why don’t we make plastics from more environmentally friendly products so that we can put them in a compost heap or industrial composter and they quickly break down into biomass, water, inorganic compounds and CO₂ leaving no toxic residue. They are then fit to spread on our land to enrich the soil.

To be truly compostable the plastic must break down at the same rate as known compostable materials such as wood, leaves or paper within three to six months of disposal. Some compostable plastics can break down even faster in just a matter of weeks.

As we all know it is no longer just a theory, many plastics can be made from natural materials such as corn starch, potato, tapioca, cellulose, soy protein and lactic acid. Some of them even look virtually indistinguishable from traditional petrochemical plastics for example Polylactide acid (PLA) looks and behaves like polyethylene and polypropylene and is now widely used for food containers.

In reality, dependent on the size and thickness of compostable plastics they may require breaking down in industrial composters and even after that may leave a residue that reduces the value of any compost produced. Aah why does there always have to be a down side!

See the table below for more details on composting rates –

ProductHome CompostingCommercial Composting
Wheat Straw or Sugarcane Fibre  Plates, Takeout Containers, Bowls, Cups and TraysUp to 6 months1-3 Months
Ingeo (brand name) Cold Cups, Clear Containers, StrawsNot recommended3-6 Months
TPLA Heat Resistant & Non Heat Resistant UtensilsNot recommended3-6 Months
Trash/Kitchen BagsUp to 1 year2-4 Months

The rate of biodegrading for different compostable plastics is dependent upon the composition and thickness of the material as well as composting conditions. Commercial composting facilities grind the materials, turn over the piles and reach high temperatures, thus reducing the amount of time it takes to compost and, is thus, the recommended method for composting these products. Home composting rates are slower and can vary, depending on how frequently the pile is turned over, the moisture and material content and the temperature.   Composting utensils such as cups lids and cutlery at home is not recommended, due to their thickness and they may not break down for few years.

Currently, just a few thousand tonnes of compostable plastics are used in the UK each year, compare that to the millions of tonnes of conventional plastic. According to Prof Simon McQueen-Mason, at the University of York we could replace half of the UK’s plastic bottles using just 3% of the sugar beet crop, 5% of wheat straw or 2.5% of food waste.

Currently the entire plastic production industry in UK has a turnover of £25bn, if the major players make the jump this new technology represents a huge economic opportunity.

But before this leap of faith we need to evaluate the overall impact of such a huge change.

1. There are of course the added environmental impacts associated with intensive agriculture, including greenhouse emissions from the petroleum needed to fuel farm machinery, and water pollution caused by runoff from land where fertilizers are used in industrial quantities.

2. Price is currently a barrier – manufacturing compostable bags is about 10 times more expensive than regular plastic bags, however as more large companies take up this type of packaging the quicker the price of production will come down. We are just at the beginning of this journey.

3. We must also bear in mind that if we mix compostable plastic with recyclable plastic it renders the recyclable plastic useless, and the whole batch will end up in landfill or burnt.

4. If we took an extreme case where all 300 million tonnes of plastic produced worldwide was made from corn starch we would need to grow an extra 795 million tonnes of corn to produce all that bioplastic (ratio of 2.65kg corn starch to 1kg bioplastic) and that is an awful lot of resources required to grown that much corn.

Based on the following figures, the average number of bushels of corn harvested per acre worldwide is 87, one bushel of shelled corn = 56lb and by calculating up we need to grow extra corn over an area 2.26 times the size of UK.

There are many new technologies appearing with regards to compostable plastics and we need to make sure we pick the right one, if not we could cause more harm than good.


So what sort of plastic is best to make a cleaner world? Not as clear cut as we first thought.

Ultimately no plastic is the best idea but at this time not realistic.

All the evidence shows that we should forget biodegradable plastic, this has a confusing name, it is neither one thing or the other and is very harmful to our environment.

Recyclable plastics are not the long term future but we must accept that for the short term at least they will be a major part of our plastic world. In which case we need to concentrate on systems to recycle as much as possible.

Compostable plastics are probably the future, but we must make sure the path is carefully thought through to make sure we do not leap into another environmental disaster.