Because thousands of tons of plastic waste are entering the world's environment every day, and will remain there for hundreds of years, unless collected for incineration.
A very small amount of pro-degradant additive is put into the manufacturing process. This breaks the molecular chains in the polymer, and at the end of its useful life the product falls apart. The plastic does not just fragment, but will be consumed by bacteria and fungi after the additive has reduced the molecular weight to a level which permits micro-organisms access to the carbon and hydrogen.
When the material has reached the fragmentation stage it is no longer a plastic, and is "biodegradable" in the same way as nature's wastes such as straw and twigs. The process continues until the material has biodegraded to nothing more than CO2, water, and humus, and it does not leave fragments of petro-polymers in the soil.
Very little, because the additive represents less than 3% of the product, and because the products can be made with the same machines and workforce as ordinary plastic.
No, because customers can still use the factories which supply them with ordinary plastic products.
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) can also emit methane. Both types are compostable, but only oxo-biodegradable can be economically recycled.
Hopefully education will reduce the litter problem over several generations, but there is a lot of 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.
Yes, and one of the benefits of oxo-biodegradable plastic is that it can be recycled as part of a normal plastic waste stream (see http://www.biodeg.org/position-papers/recycling/?domain=biodeg.org) However, if the plastic is not collected it cannot be recycled, so it needs to biodegrade instead of accumulating in the environment.
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.
Oxo-biodegradable plastic does not degrade quickly in low temperature "windrow" composting, but it is suitable for "in-vessel" composting at the higher temperatures required by the new EU animal by-products regulations. Indeed it is likely that windrow composting will soon have to be phased out.
Oxo-biodegradable plastics fragment and partially biodegrade to CO2 and water in the parts of the landfill where oxygen is present, but the residues are completely inert deeper in the landfill in the absence of oxygen. They do not emit any significant amounts of methane.
By contrast, hydro-biodegradable (starch-based) plastics will degrade and emit CO2 in a landfill if there is enough microbial activity. However, in the depths of a landfill, in the absence of air, hydro-biodegradable plastics generate copious quantities of methane, which is a powerful greenhouse gas.
No. It contains transition metal ions of Cobalt or Iron or Manganese, which are trace elements required in the human diet. They should not be confused with toxic heavy metals such as Lead, Mercury, Cadmium and Chromium, which are never used in oxo-biodegradable plastics.
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 wasting it by "flare-off" at the refinery and using scarce agricultural resources to make plastics. In fact plastics could reduce the amount of oil and gas imported because after their useful life they can be incinerated to release the stored energy, which can be used to generate electricity or to heat buildings.
Recently, interest has been shown in manufacturing sugar-derived polyethylenes. These, like oil-derived PE, are not biodegradable, but they can be made oxo-biodegradable in the same way as the latter, by the addition of a pro-degradant additive.
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. Fossil fuels are burned in the machines used to 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 used to ferment and polymerise material synthesised from biochemically produced intermediates (e.g. polylactic acid from carbohydrates etc). When the material biodegrades it emits CO2 and methane, so the total fossil fuels used and greenhouse gases emitted are more than for conventional or oxo-biodegradable plastic.
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.
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.
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 international standards.
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 on land 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.
Degradable plastic bags have been supplied by supermarkets for more than four 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.
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.
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 discarded plastic were all oxo-biodegradable?
Yes. Oxo-biodegradable plastic has been certified by RAPRA Technology Analytical Laboratories as safe for long-term contact with any food type at temperatures up to 40°C. RAPRA is accredited by the United Kingdom accreditation authorities as meeting the requirements of International Standards Organisation norm no. 17025. It is also certified as compliant with FDA requirements in the US.
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. However the EU Packaging Waste Directive does NOT require that when a packaging product is marketed as "degradable" or "compostable" conformity with the Directive must be assessed by reference 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, such as a report from a reputable body. Indeed Annex Z of EN13432 itself says that it provides only one means of conforming with the essential requirements.
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.
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 plastic and will last for 3-5 years.
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 about 18 months, 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.
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.
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.
Until recently there was no standard in Europe designed to test oxo-biodegradable plastic.
However, In July 2007 the French Standards organisation, AFNOR, published XP T 54-980, which is a Standard for oxo-biodegradable plastics in agriculture.
A draft standard 8472 capable of measuring oxo-biodegradation is being developed by the British Standards Institution.
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 emission of carbon dioxide during degradation. Hydro-biodegradable plastic is compliant with EN 13432, precisely because it emits CO2 (a greenhouse gas) at a high 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.
Conversion of organic materials to CO2 at a rapid rate during the composting process is not "recovery" as required by the European Directive on Packaging and Packaging Waste (94/62/EC as amended), and should not be part of a standard for composting. Nature's lignocellulosic wastes do not behave in this way, and if they did the products would have little value as soil improvers and fertilisers, having lost most of their carbon.
If a leaf were subjected to the CO2 emission tests included in EN13432 it would not be considered biodegradable or compostable!
Packaging made from oxo-biodegradable plastic complies with para. 3(a), (b) and (d) of Annex II of the European Parliament and Council Directive 94/62/EC (as amended) on Packaging and Packaging Waste. This Annex specifies the essential requirements for the composition, and the reusable and recoverable, including recyclable, nature of packaging.
Oxo-biodegradable plastic satisfies para. 3(a) because it can be recycled. It satisfies para. 3(b) because it can be incinerated. It satisfies para. 3(d) because it is capable of undergoing physical, chemical, thermal or biological decomposition such that most of the finished compost ultimately decomposes into carbon dioxide, biomass and water.