Position Papers
Types of Degradable Plastic
It is important to distinguish between the different types of biodegradable plastic, as their costs and uses are very different.
The two main types are oxo-biodegradable and hydro-biodegradable. In both cases degradation begins with a chemical process (oxidation and hydrolysis respectively), followed by a biological process. Both types emit CO2 as they degrade, but hydro-biodegradable can also emit methane. Both types are compostable, but only oxo-biodegradable can be economically recycled.
Hydro-biodegradable is much more expensive than oxo-biodegradable.
OXO-BIODEGRADABLE PLASTIC
This new technology produces plastic which degrades by a process of OXO-degradation. The technology is based on a very small amount of pro-degradant additive being introduced into the manufacturing process, thereby changing the behaviour of the plastic. Degradation begins when the programmed service life is over (as controlled by the additive formulation) and the product is no longer required.
There is little or no additional cost involved in products made with this technology, which can be made with the same machinery and workforce as conventional plastic products.
The plastic does not just fragment, but will be consumed by bacteria and fungi after the additive has reduced the molecular structure to a level which permits living micro-organisms access to the carbon and hydrogen. It is therefore "biodegradable." This 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. 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 ON S 2200 and ON S 2300 national standards.
Oxo-biodegradable film has been certified as safe for long-term contact with any food type at temperatures up to 40°C, and oxo-biodegradable bags are being bought and distributed by the UK Soil Association, and used for direct contact with organic food products.
Oxo-biodegradable plastic products are now being supplied by the leading UK supermarkets, Tesco and the Co-op. In Portugal the country's largest retail group, Sonae, has adopted oxo-biodegradable plastic carrier bags for their Continente, Mondelo and Mondelo Bonjour supermarket chains. Other major users include Marriott, Royal Caribbean Cruise Lines, BUPA, News International, Pizza Hut, KFC, and Walmart. Oxo-biodegradable plastic is ideal for frozen food packaging, as it can be kept for extended periods at low temperature, and will then quickly degrade when it becomes a waste product at normal temperatures.
In May 2007 the Periodical Publishers Association of the UK recommended to all its members that oxo-biodegradable film should be used for wrapping their newspapers and magazines for distribution.
The length of time it takes for oxo-biodegradable products to degrade can be ‘programmed' at the time of manufacture and can be as little as a few months or as much as a few years. They are protected from degradation by special antioxidants until ready for use, and storage-life will be extended if the products are kept in cool, dark conditions.
Unlike PVC, the polymers from which oxo-biodegradable plastics are made do not contain organo-chlorine. Nor do oxo-biodegradable polymers contain PCBs, nor do they emit methane or nitrous oxide even under anaerobic conditions.
Fossil Resources
Oxo-biodegradable plastics are currently made from naptha, which is a by-product of oil refining, and oil is of course a finite resource. However, this by-product arises because the world needs fuels and oils for engines, and would arise whether or not the by-product were used to make plastic goods.
Unless the oil is left under the ground, carbon dioxide will inevitably be released, but 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.
A Life Cycle Assessment was carried out in January 2005 by GUA - (Gesellschaft für umfassende Analysen) of Vienna which shows that:
"Plastic products are made of energy resources. Additionally, their production needs further energy resources. Nevertheless, plastic products frequently enable energy savings from the perspective of the energy balance of the total life cycle compared to the energy balance of an alternative material. Examples for such energy savings by plastic products are:
Substitution of materials which consume much more energy for production of the same functional unit (e.g. glass)Performance of a certain function with much less material (e.g. packaging)Fuel savings because of reduction in mass (transport)Energy savings due to thermal insulation (where insulation with other materials would be less effective, technically complicated or too expensive)Savings of resources by avoiding loss or damage of packed products."Recently, interest has been shown in manufacturing sugar derived polyethylenes. These, like fossil-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.
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 the advantages of oxo-biodegradable products are not mutually exclusive. If people want to incinerate with heat recovery, or mechanically recycle them, 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.
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.
HYDRO-BIODEGRADABLE PLASTICS
Hydro-biodegradation is initiated by hydrolysis.
Some plastics in this category have a high starch content and it is sometimes said that this justifies the claim that they are made from renewable resources. However, many of them contain up to 50% of synthetic plastic derived from oil, and others (e.g. some aliphatic polyesters) are entirely based on oil-derived intermediates. Genetically-modified crops may also have been used in the manufacture of hydro-biodegradable plastics.
Hydro-biodegradable plastics are not genuinely "renewable" 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 autoclaves used to ferment and polymerise material synthesised from biochemically produced intermediates (e.g. polylactic acid from carbohydrates etc); and by the agricultural machinery and road vehicles employed; also by the manufacture and transport of fertilisers and pesticides. They are sometimes described as made from "non-food" crops, but are in fact usually made from food crops.
A disproportionate amount of land would be required to produce sufficient raw material to replace conventional plastic products, and a huge amount of water, which is in such short supply in so many parts of the world.
Residues from some native starches can be seriously toxic; bitter cassava for example (tapioca) has a high level of hydro-cyanic glucoside present, which has to be removed by careful washing. During growth the plant is toxic to wildlife. Cassava is exhaustive of potash .
Three recent articles in the international press have drawn attention to the danger of using "renewable" resources derived from plants as a substitute for petroleum products. They focus on the use of corn and palm oil to make "biofuels" for motor vehicles, but the same danger arises from the use of corn and other agricultural products to make hydro-biodegradable plastics.
The International Herald Tribune wrote on 31st January 2007 "Just a few years ago politicians and green groups in the Netherlands were thrilled by the country's adoption of "sustainable energy" by coaxing electricity plants to use biofuel. Spurred by government subsidies, energy companies designed generators that ran exclusively on this fuel, which in theory would be cleaner than fossil fuels because it is derived from plants.
But last year, when scientists studied plantations in Indonesia and Malaysia, this green fairy-tale began to look more like an environmental nightmare. Rising demand for palm oil in Europe caused the razing of huge tracts of southeast Asian rain forests, and the over-use of chemical fertilisers there. Worse still, space for the plantations was often created by draining and burning peat land, which sent huge carbon emissions into the atmosphere.
In Mexico on 25th January the financial newspaper "24 ORE" asked "Food or fuel? Is maize better on the table as tortillas or in the tanks of cars, converted into ethanol and then bio-fuel? The price of the cereal has doubled in a year because of the high demand for ethanol obtained from maize to produce bio-fuels. It has created a real food crisis because the price of tortillas has increased greatly. They used to cost seven pesos per kilo but now exceed 18 pesos. Tortillas are the basic element of the Mexican diet.
According to the Earth Policy Institute, "The trade off between food and fuel risks creating chaos in the world market of food products" and they predict that shortages and higher food prices will lead to starvation and urban riots
Business Week 5 Feb 2007 edition "The rise in the price of corn that's hurting US pig farmers isn't caused by any big dip in the overall supply. In the U.S., last year's harvest was 10.5 billion bushels, the third-largest crop ever. But instead of going into the mouths of pigs or cattle or people, an increasing slice is being transformed into fuel for cars. The roughly 5 billion gallons of ethanol made in 2006 by 112 U.S. plants consumed nearly one-fifth of the corn crop." US chicken producers are also being hit. The industry's feed costs are already up $1.5 billion per year. Ultimately, these increases will be passed on to consumers, and there could be dramatic inflation in food costs.
The UK House of Commons Environmental Audit Committee has found that "the stimulation of biofuels production by the [UK] Government and EU is reckless in the absence of effective mechanisms to prevent the destruction of carbon sinks internationally"
The Committee continued "A large biofuel industry based on current technology is likely to increase agricultural commodity prices and, by displacing food production, could damage food security in developing countries."
The use of biofuels in the EU have come under assault once again, this time from the European Commission's own scientific institute, the Joint Research Centre. An unpublished internal report from the research body questions whether the cost of their use is worth the benefits.
The report buttresses worries over biofuels expressed by environment commissioner Stavros Dimas and research from environmental campaign groups that suggests biofuels may actually contribute to global warming through the deforestation and peat bog burning that is required for biofuel sources such as corn or oil palm trees.
The British Royal Society for the Protection of Birds is also highly critical of using land and water resources for this purpose "Driven by the thoughtless policies of governments around the world, biofuels production is decimating swathes of important habitat and threatening the survival of many species, including Sumatran tigers, orang utans and countless bird species.Biofuels advocates justify this destruction by citing their potential for combating climate change. However, whilst biofuels can play a part, many of those on the market today don't deliver the greenhouse gas savings they promise and some are even more polluting than the fossil fuels they're meant to replace. There is also evidence to suggest that taking land used for growing food, and converting it to growing biofuels, is reducing the amount of food produced and contributing to increasing prices."
On 6th March 2008 the United Kingdom's Chief Scientific Adviser warned that if this continues the world will soon be unable to feed itself.
Recycled plastics are OK, but they are not degradable and will still lie around in the environment for decades. However, ordinary plastic and recycled plastic can now be made oxo-biodegradable.
This is done by including d2w additive (see www.d2w.net) which makes it degrade, then biodegrade, on land or at sea, in the light or the dark, in heat or cold, in whatever timescale is required, leaving NO fragments NO methane and NO harmful residues. Oxo-bio passes the tests in American Standard 6954, and is made from a by-product of oil refining which used to be wasted, so nobody is importing extra oil to make it.
There is little or no additional cost.
Plastics made from crops, are up to 400% more expensive, they are not strong enough for use in high-speed machinery, and they emit methane (a powerful greenhouse gas) in landfill. Also, it is wrong to use land, water and fertilisers to grow crops for bioplastics and biofuels, which drives up the cost of food for the poorest people. See also The Guardian 26th April 2008
The same applies to growing cotton or jute to make durable bags. These rapidly become unhygienic if a tomato is squashed or milk spilled, and they become a durable form of litter, but they can be made from washable oxo-bio plastic, to last up to 5 years.
Oxo-bio plastics degrade in the upper layers of a landfill, but they are completely inert deeper in the landfill in the absence of oxygen. They do not emit methane at any stage.
Paper bags use 300% more energy to produce, they are bulky and heavy and are not strong enough, especially when wet. They will also emit methane in landfill
For the reasons given under "Composting," compostability of plastics is an irrelevance
PHOTO-DEGRADABLE PLASTICS
These react to ultra-violet light, but unless they are also oxo-biodegradable they will not degrade in a landfill, a sewer, or other dark environment, or if heavily overprinted.
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1. sub 40,000 Daltons
2. Oxo-degradation is defined by TC249/WG9 of CEN (the European Standards Organisation) as "degradation identified as resulting from oxidative cleavage of macromolecules." And oxo-biodegradation as "degradation identified as resulting from oxidative and cell-mediated phenomena, either simultaneously or successively."
3. See G. Scott and D.M. Wiles, Degradable Polymers: Principles and Applications, Kluwer, 2002, Chapter 13, Section 9.11, page 472, et seq.
4. RAPRA cert 19th March 2007. Compliant with European Directives 2002/72/EC (as amended 2004/19/EC).
5. Pyxis CSB "Comparative Life Cycle Analyses for a variety of Degradable Food Packaging Materials" June 2007
6. Report 15th January 2008 (HC 76-1 of 2007-08). Para 53
7. ibid para 63
8. The Times 7th March 2008
The Guardian 26th April 2008