What is oxo-biodegradable plastic?
Oxo-biodegradable plastic is ordinary plastic to which small amounts of metal salts (a prodegradant additive) has been added during the manufacturing process. The resulting plastic is then made into products like carrier bags, produce or courier bags, straws and other short-life/single-use items. The big difference between oxo-biodegradable and ordinary plastic is that if oxo-biodegradable plastic escapes collection and ends up in the open environment as litter, it will degrade and biodegrade in a similar way to nature’s waste.
How does it work?
In the presence of oxygen, the prodegradant additive breaks the molecular chains in the polymer, and at the end of its useful life the product will degrade and biodegrade, that is it will be consumed by bacteria and fungi, after the additive has reduced the molecular weight to a level which permits them access to the carbon and hydrogen.
Why do we need oxo-biodegradable plastic?
Because thousands of tons of plastic waste are entering the world’s environment every day, and will remain there for decades. In no country is it possible to collect all the plastic for recycling or other forms of responsible disposal.
Does oxo-biodegradable plastic biodegrade, or does it just fragment?
Oxo-biodegradable plastic does just what it says, the clue is in the name – It is called oxo-biodegradable plastic because it is biodegradable. Oxo-biodegradable technology converts plastic products into biodegradable materials at the end of their useful life, and it does this by oxidation in the presence of oxygen. There is nothing misleading about it.
There are some scientists who are not expert in oxo-biodegradable technology and there are mischievous individuals or companies who are spreading misinformation because they wish to give their own product an advantage in the marketplace that it does not deserve on merit. A scientific team from Blaise Pascal University (France’s leading research centre into degradable plastics) took issue with the erroneous ‘not very expert reports’ and misinformation by which the EU has been misled on this issue http://www.biodeg.org/CNEP%20Stmt%20Nov%202014%20(En)-Lemaire%20appvd(1).pdf
Oxo-biodegradable plastic degrades and biodegrades in the open environment in the same way as nature’s wastes. What’s more, it does so without leaving any toxic residues or fragments of plastic behind. If oxo-biodegradable plastic merely fragmented without biodegrading, CEN (European Committee for Standardization)would not have defined oxo-biodegradability as “degradation resulting from oxidative and cell-mediated phenomena, either simultaneously or successively” and the American, British and French standards organisations would not have included tests for biodegradability in ASTM D6954, BS8472 and ACT51-808.
Oxo-biodegradable plastic has been studied by scientists for many years http://www.biodeg.org/bibliography.html most recently at the Technical Research Institute of Sweden and the Swedish University of Agricultural Sciences, and a peer-reviewed report of the work was published in Vol 96 of the journal of Polymer Degradation & Stability (2011) at page 919-928. They found 91% biodegradation within 24 months.
Furthermore, ten governments in the world have examined this technology very carefully and realised that oxo-biodegradable plastic offers a solution to plastic waste that escapes into the open environment and cannot realistically be collected. They have legislated to make oxo-biodegradable plastic mandatory, because it does not just fragment. It biodegrades.
The process continues until the material has biodegraded to nothing more than CO2, water, and humus. It does not leave fragments of petro-polymers in the soil.
What does it cost?
Very little, because the additive represents only 1% of the polymer, and because the products can be made with the same machines and workforce as ordinary plastic.
Can it be recycled?
Yes – if collected, it can be recycled alongside ordinary household plastic.
Won’t it put existing factories out of business, with loss of jobs?
No, because commercial customers can still use the factories which supply them with ordinary plastic products.
What types of biodegradable plastics exist?
The two main types are oxo-biodegradable and hydro-biodegradable. In both cases degradation begins with a chemical process (oxidation or hydrolysis), followed by a biological process. Both types emit CO2 as they degrade, but hydro-biodegradables (usually starch-based) will also emit methane under anaerobic conditions eg deep in landfill. Only oxo-biodegradable can be economically recycled.
What are the differences between oxo-biodegradable and hydro-biodegradable plastic?
Surely education is the way to solve the litter problem?
Hopefully education will reduce the litter problem over several generations, but there is a huge amount of plastic litter today and there will always be some litter. Action needs to be taken today to switch to oxo-biodegradable before millions more tons of plastic waste accumulate in the environment. This what the United Arab Emirates, Pakistan and other countries have now done by law, and other countries will be doing.
Isn’t it better to recycle than to let it biodegrade?
Yes, and one of the benefits of oxo-biodegradable plastic is that it can be recycled as part of a normal plastic waste stream (seehttp://www.biodeg.org/recycling.html However, if the plastic is not collected it cannot of course be recycled, so it needs to degrade instead of accumulating in the environment.
What about energy recovery?
In some countries incineration is popular, and modern equipment is in place. Oxo-biodegradable plastic can be incinerated with energy recovery in the same way as conventional plastic, and has a higher calorific value than the hydro-biodegradable alternative.
Can it be composted?
Oxo-biodegradable plastic does not degrade quickly in low temperature “windrow” composting, and it will not therefore pass the tests in EN13432 in the timescale there specified, but it is suitable for “in-vessel” composting at the higher temperatures required by the new EU animal by-products regulations.
What happens to it in a landfill?
Oxo-biodegradable plastics fragment and partially biodegrade to CO2 and water in the parts of the landfill where oxygen is present, but degradation cannot continue deeper in the landfill in the absence of oxygen.
By contrast, hydro-biodegradable (starch-based) plastics will degrade and emit CO2 in a landfill. However, in the depths of a landfill, in the absence of air, hydro-biodegradable plastics generate methane, which is a powerful greenhouse gas.
Does oxobio plastic contain “heavy metals”?
No. It contains metal salts, which are trace elements required in the human diet. They should not be confused with toxicheavy metals such as Lead, Mercury, Cadmium and Chromium, which are never used in oxo-biodegradable plastics.
Isn’t it made from oil?
Yes. Oxo-biodegradable plastics are currently made from a by-product of oil or natural gas. These are of course finite resources, but the by-product arises because the world needs fuels, and would arise whether or not the by-product were used to make plastic goods.
Until other fuels and lubricants have been developed for engines, it makes good environmental sense to use the by-product, instead of using agricultural resources to make plastics.
Recently, interest has been shown, especially in Brazil, in manufacturing sugar-derived polyethylenes. These, like oil-derived PE, are not biodegradable, but they can be made oxo-biodegradable in the same way, by the addition of a pro-degradant additive.
But aren’t the hydro-biodegradable plastics renewable?
No – because the process of making them from crops is itself a significant user of fossil-fuel energy and a producer therefore of greenhouse gases. See http://www.biodeg.org/Hydro-biodegradable%20Plastic%20Production%20Process.pdf
Fossil fuels are burned and CO2 is emitted by the machines which clear and cultivate the land, and in the manufacture and transport of fertilisers and pesticides and in transporting the crop itself. Energy is also used by the autoclaves which polymerise material synthesised from biochemically produced intermediates (e.g. polylactic acid from carbohydrates etc). When the material biodegrades it emits CO2 and can emit methane, so the total fossil fuels used and greenhouse gases emitted will be more than for conventional or oxo-biodegradable plastic.
In June 2009 Germany’s Institute for Energy and Environmental Research concluded that oil-based plastics, especially if recycled, have a better Life-cycle Analysis than compostable plastics. This was also the conclusion of two LCAs done by Intertek http://www.biodeg.org/lifecycleassessments.html
Hydro-biodegradables are sometimes described as made from “non-food” crops, but are in fact usually made from food crops, and drive up the price of human and animal food.
Does oxobio plastic leave any harmful residues?
No. Oxo-biodegradable plastic passes all the usual ecotoxicity tests, including seed germination, plant growth and organism survival (daphnia, earthworms) tests carried out in accordance with OECD standards.
Deliberately and totally lost?
The argument that oxo-biodegradable plastics are undesirable because their components are designed to be deliberately and totally lost is a fallacy, because if people want to incinerate with heat recovery, or mechanically recycle them, or compost them in-vessel, or re-use them, then that’s OK, and they cost very little if anything more than conventional products. The key point is what happens to the plastic which is not collected, and gets into the environment as litter?
In any event, oxo-biodegradable plastics are not “deliberately and totally lost” even if they degrade in the environment, because biodegradation is a source of plant nutrients, just as is straw, grass, leaves etc.
By contrast, hydro-biodegradable plastics ARE “deliberately and totally lost” because the applicable international standards require them to convert to CO2 gas within 180 days.
More Careless disposal?
Degradable plastic bags have been supplied by supermarkets for more than ten years, but there is no evidence that people dispose more carelessly of them (whether oxo or hydro biodegradable) and they have not been encouraged to do so. The type of person who causes litter will not bother to look for a biodegradable label before tossing it out of a car window.
But suppose for the sake of argument that 10% more were discarded. If 1,000 conventional and 1,100 oxo-biodegradable bags were left uncollected in the environment, 1,000 conventional bags would remain in the rivers, streets and fields for decades, but none of the oxo-biodegradable bags would be left at the end of the short life programmed into them at manufacture.
As there will always be people who will deliberately or accidentally discard their plastic waste, what will happen to all the plastic waste that will not be recycled or will not be incinerated, and instead will litter the countryside – would it not be better if the plastic were all oxo-biodegradable? If all the plastic has been oxobio there would be no ocean garbage patches.
Is it safe for food-contact?
Can oxo-bio be marketed as Biodegradable or Compostable?
Yes (except in California). A court in the US court ruled in February 2015 that it is not necessary to prove complete biodegradation, nor within any particular timescale.
On 8th April 2010 the Advertising Standards Authority of South Africa ruled that bread bags made with oxo-biodegradable plastic can be advertised as Biodegradable.
The current EU Standard for composting (EN13432) is not appropriate for testing oxo-biodegradable plastic. The EU Packaging Waste Directive does NOT require that when a packaging product is marketed as “degradable” or “compostable” it must be assessed according to EN13432. The Directive provides that conformity with its essential requirements may be presumed if EN 13432 is complied with, but it does not exclude proof of conformity by other evidence. Indeed Annex Z of EN13432 itself says that it provides only one means of conforming with the essential requirements.
Isn’t it better to use paper bags?
No. The process of making paper bags causes 70% more atmospheric pollution than plastic bags. Paper bags use 300% more energy to produce, and the process uses huge amounts of water and creates very unpleasant organic waste. When they degrade they emit methane and carbon dioxide.
A stack of 1000 new plastic carrier bags would be around 2 inches high, but a stack of 1000 new paper grocery bags could be around 2 feet high. It would take at least seven times the number of trucks to deliver the same number of bags, creating seven times more transport pollution and road congestion.
Also, because paper bags are not as strong as plastic, people may use two or three bags inside each other. Paper bags cannot normally be re-used, and will disintegrate if wet.
Isn’t it better to use durable re-usable bags?
No. Long-term re-usable shopping bags are not the answer. They are much thicker and more expensive, and a large number of them would be required for the weekly shopping of an average family. They are not hygienic unless cleaned after each use. Whilst sometimes called “Bags for Life” they have a limited life, depending on the treatment they receive, and become a very durable problem when discarded.
Shoppers do not always go to the shop from home, where the re-usable bags would normally be kept, and consumers are unlikely to have a re-usable bag with them when buying on impulse items such as clothing, groceries, CDs, magazines, stationery etc.
However, for those who believe in long-term re-usable bags, they can be made from extended-life oxo-biodegradable washable plastic containing an anti-microbial additive.
How long does it take to degrade?
An important advantage of oxo-biodegradable plastic is that it can be programmed to degrade in whatever timescale is required. The average useful life of a carrier bag is usually designed to be about 18 months (to allow for distribution, stocking, and re-use), but shorter or longer times are possible. During that time bags are often re-used for shopping or for use as bin-liners etc. Heat and light will accelerate the process, but they are not essential. If discarded in the outdoor environment at the end of its useful life it will degrade and biodegrade much more quickly than conventional plastic. Timescale for the abiotic phase can be predicted by laboratory tests, but it is not necessary or possible to predict timescale for subsequent biodegradation.
What products are available in oxo-biodegradable plastic?
Carrier bags or “shopper-bags” which consumers use to take away their purchases from the shop
Refuse sacks, which consumers buy in rolls at the shop, and use for disposal of their ordinary household waste.
Aprons, for the protection of garments, in the home, hospitals, restaurants, workshops etc.
Bags to contain dog faeces collected in parks, gardens, etc
Plastic sheeting for a variety of applications in agriculture and horticulture.
Plastic film for wrapping newspapers and magazines.
Frozen food bags
Wrappers for cigarette packets
Shrink-wrap and pallet-wrap
Rigid products such as bottles and cups
More products will become available in due course.
What national or international standards exist?
Oxo-biodegradable plastic can be tested according to American Standard ASTM D6954-04 for Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation. Also, according to British Standard 8472, or UAE Standard 5009 of 2009, or the French Accord T51-808.
The French Standards organisation, AFNOR, has also published XP T 54-980, for oxo-biodegradable plastics in agriculture.
UAE No: 5009/2009 The Emirates Authority for Standards & Metrology (ESMA) has developed , implemented and enforced on October 26, 2009 the UAE Technical Regulation Standards: 5009/2009; with the title Standard & Specification for Oxo-biodegradation of Plastic Bags and other Disposable Plastic Objects.
SAUDI Standard: SASO 2879/2016 – Saudi Standards, Metrology and Quality Org (SASO) has developed, implemented and enforced in April 2016 the Specification 2879/2016 with the title Degradable Plastic Products.
The above two standards (UAE and Saudi)m which include complete Pass/Fail criteria are the most recent oxo-biodegradable standards in use around the globe.
European standard EN 13432 applies only to plastic packaging, and was written before oxo-biodegradable plastics became popular. It is not appropriate for testing oxo-biodegradable plastics because it is based on measuring the rapid emission of carbon dioxide during biodegradation. Hydro-biodegradable plastic is compliant with EN 13432, precisely because it emits CO2(a greenhouse gas) at a rapid rate.
Another unsatisfactory feature of EN 13432 is that it requires almost complete conversion of the carbon in the plastic to CO2, thus depriving the resulting compost of carbon, which is needed for plant growth, and wasting it by emission to atmosphere.