Erasmus : There is currently an increasing emphasis on the development of biodegradable plastic polymers as a long-term solution for eliminating many of our current plastics from landfills and from the environment.
These materials are designed to degrade on exposure to UV and/or microorganisms. Common source materials include starch, cellulose, and polyesters. Biodegradable polymers can also be produced from polyesters created by the bacterial fermentations of sugars and lipids that are extracted from plants.
(Polyesters isolated from fermentation reactions include: direct reaction byproducts such as PHA, xanthan and Pullulan; and Monomers such as PLA and TPA that are derived from lactic acid and aspartic acid produced in fermentation).
Starch and cellulose are commonly called biopolymers because they are produced by plants and then blended with polymers to produce composite materials that are biodegradable.
Commercially, hydrocarbon derived plastic polymers are substantially cheaper than alternate polymers derived from industrially or microbiologically produced feedstock chemicals. The biodegradable polymers are desirable but they are much less economically viable than our current alternatives.
Kinkajou : An alternative approach would be to emphasise plastics materials that are less toxic to the environment, derived from our standard hydrocarbon feedstocks. We don’t need to reinvent the wheel.
We just need to choose end products for many of our currently used reactions that are more biodegradable, or we need to choose manufacturing processes that combined products into more biodegradable finished goods.
Kinkajou : Over the past three decades, the quantity of plastics recycled has increased annually. However recycling rates for plastics substantially lag behind the recycling rates for newspaper (approximately 80%) and cardboard (approximately 70%).
Each group of plastic polymer can be identified by its Plastic Identification code (PIC), usually a number or a letter abbreviation.
Glass Transition Temp°C
Young's Modulus GPa
240 (only isotactic)
100 (atactic and isotactic)
Polycarbonate: 2.6; ABS plastics: 2.3
War Time Recycling
Polyethylene terephthalate (PET, PETE) resin code 1
Properties Clarity, strength, toughness, barrier to gas and moisture
Common Packaging Applications:
- Soft drink ,water bottles, Commercially bottles foodstuffs : inc. salad dressing bottles, peanut paste and jam jars;
- Recycled PET has been widely used to produce polyester fibres. Generally these fibres are used to create hard wearing products such as jackets and coats, shoes, bags and hats. They are usually used for over the top accessories as they generally too rough for direct skin contact and can irritate.
- Small consumer electronics.
- Approximately 60% of recycled PET is used for injection stretch blow moulding into bottles and jars or by injection moulding of engineering components, incorporating into building materials or by heat moulding PET sheets to produce containers, blister packs, or trays.
High-density polyethylene (HDPE) resin code 2
Properties: Stiffness, strength, toughness, resistance to moisture, permeability to gas.
Common Packaging Applications:
- Plastic timber like material, external tables, roadside guttering and pipework, benches, or trash bins.
- Most hard plastics such as Water pipes, large water buckets ,
- milk jugs, laundry detergent bottles , some milk, juice and water bottles;
- Grocery bags, some shampoo/toiletry bottles.
- Some dishware.
Polyvinyl chloride (PVC), resin code 3
Properties: Versatility, ease of blending, strength, toughness.
Common Packaging Applications:
- Blister packaging for non-food items; cling films for non-food use.
- Shower curtains, bedding plastics
- May be used for food packaging with the addition of the plasticisers needed to make natively rigid PVC flexible.
- Non-packaging uses are wiring jackets, electrical cable insulation; rigid piping;
Low-density polyethylene (LDPE), resin code 4
Properties: Ease of processing, strength, toughness, flexibility, ease of sealing, barrier to moisture.
Common Packaging Applications
- Shopping bags ,Frozen food bags;
- squeezable bottles, e.g. food uses;
- Flexible container lids.
- Tote bags, clothing, furniture and carpet.
Polypropylene (PP), resin code 5
Properties: Strength, toughness, resistance to heat, chemicals, grease and oil, versatile, barrier to moisture.
Common Packaging Applications:
- Reusable cooking ,kitchen and tableware: yogurt containers; margarine tubs, disposable cups;
- microwaveable ware, microwaveable disposable take-away containers;
- Soft drink bottle caps.
- Syrup bottles, straws, Tupperware.
Polystyrene (PS), resin code 6
Properties: Versatility, clarity, easily formed
Common Packaging Applications:
- Egg cartons; meat trays
- Packing shapes or pellets,
- Light disposable cups,
- Older style insulating disposable food take-away containers.
- Clothes hangers, plant pots and seedling containers, children’s toys, rulers and some outdoor furniture like park benches or external tables
- Recycled EPS is also used in many metal casting operations
Due to logistical collection constraints (especially volume and low weight), polystyrene is rarely recycled although it is quite amenable to many recycling process.
Plastics in Recycling
Other (often polycarbonate or ABS), resin code 7
Properties: Dependent on polymers or combination of polymers
Common Packaging Applications:
- Beverage bottles; baby milk bottles.
- Polycarbonate: compact discs;
- "Unbreakable" glazing; electronic apparatus
- Bulletproof materials, safety glasses or sunglasses
Kinkajou : what is your opinion of the crisis in the availability of landfill space?
Erasmus : The crisis in landfills a few decades ago was really a crisis about cost rather than space. Several decades ago, old landfill sites had become to approach their end-of-life and had begun to cease operation. A number of events occurred in sequence for a number of reasons.
With the emphasis on environment protection, new landfill sites had to meet tougher operating standards and to be more environmentally safe. The availability of landfill space varies over time.
You would also expect that landfill prices would tend to be highest in areas of the population density is greatest and the land is the most expensive.
The most likely landfill sites ended up being those that were closest to high-density population centres, coincidently these being areas where the prices for landfill sites were the most expensive.
As the old landfill city sites closed, the only available dumps were the many small unregulated town dumps. These were ill suited to the demands placed upon them, and were replaced by regional dumps servicing high-density city areas with higher environmental safety standards but which were substantially more expensive than prior sites.
One of the main drivers for the use of landfill was in fact to provide an alternative to incineration of rubbish. Again in earlier times, pollution from incineration was becoming an environmental issue, standards were lower and energy generation had not been considered as an alternative to simple burning of waste.
The major goals of the recycling movement were to reduce environmental pollution of the air and of groundwater, to reduce energy used in manufacturing (cf compared to energy requirements for the provision of virgin materials), and to reduce environmental degradation resulting from mining practices such as open cut mining.
Kinkajou : There are some very special materials that require recycling.
Erasmus : It is understandable that large metal objects such as tanks, ships and automobiles are recycled. In large quantities, metal is able to be recycled in a commercially viable format. However there are some unusual materials which require special consideration.
Kinkajou : Like What?
Erasmus : Uranium is left over from any nuclear industrial processes. Depleted uranium is reprocessed into armour piercing shells and shielding.
Kinkajou : How dangerous is that?
Erasmus : Depleted uranium is use in such uses as radiation shielding, containers for radio materials and for military uses such as incorporation into armour or ballistic weaponry.
Uranium is very dense, approximate 70% denser than lead. It is preferred in military applications because the nose of depleted uranium rounds fractures in such a way as to remain sharp, enabling penetration and because it is flammable upon penetration into the interior of an armoured vehicle.
Alternatives include some of the tungsten alloys such as tungsten cobalt or tungsten nickel cobalt. However these heavy metals also possess carcinogenic properties which are reputed to exceed those of depleted uranium itself.
Some researchers have unveiled research suggesting that many rats implanted with a tungsten nickel cobalt pallet into the abdominal cavity, developed rhabdomyosarcoma within weeks.
Goo : I know something about health and immunity in small mammals. Rats develop cancer with many drugs and chemicals, but such findings are generally considered not relevant to humans. While we use rats in screening for carcinogenicity and teratogenicity in many chemicals, the relevance to humans can be difficult.
Dr Xxxxx : Yes we had multiple concerns that simple acid suppressing drugs called proton pump inhibitors use in humans could be responsible for neuroendocrine tumours in human beings using these medications. Prolonged use in humans has shown that this has not occurred.
Erasmus : a number of countries have attempted to promote bans on the use of depleted uranium in ammunition and armour.
Only France and Britain, the main nuclear countries in the European Parliament have shied away from supporting moratorium on the use of depleted uranium ammunition. Much of the argument seems to be splitting into nuclear/nonnuclear nation blocks and NATO versus non-NATO country blocks.
Kinkajou: I think the jury is out for the moment, on the use of depleted uranium in armour and ammunition.
Kinkajou : There are several sorts of recycling we have not mentioned yet.
Erasmus : Sewage treatment is a very important form of recycling. This can be done locally as in septic technology including modern modifications such as bio-reactors. It can also be complex through modern multistage treatment plants to reduce solid waste and to minimise water or ocean contamination.
- bioreactors: responsible for oxidation of waste
- composting and
Kinkajou : Tell us about the Sewage Treatment process
Sewage in Australia, goes through three treatment stages to produce Class A recycled water.
Sewerage treatment Luggage point Brisbane
Erasmus : Sewage today in the Western world undergoes 3 levels of treatment:
Erasmus :Primary treatment
Primary treatment includes:
- filtering out large objects like cotton buds, rags and other rubbish, using fine screens
- aerating the sewage to remove finer particles like grit and sand
- sedimentation, where heavy items sink to the bottom forming a layer called sludge – the settled sludge and floating debris is pumped to larger tanks, known as digesters, where it is broken down by bacteria
Erasmus : Secondary treatment
In secondary treatment, different types of bacteria exist side by side in aerobic (with oxygen) and anoxic (without oxygen) environments, breaking down organic material and removing nutrients in the plant's aeration tanks.
The water then passes through sedimentation tanks where more sludge settles to the bottom to finally produce clear treated water at the top, also known as secondary effluent.
The treated secondary effluent flows to large holding ponds before it enters the tertiary treatment stage of the plant.
Erasmus : Tertiary treatment
- This process adds several additional steps including:
- ozone and UV disinfection
- biological filtration to reduce ammonia, oil and grease, foam, litter and solids
The tertiary supply pump lifts effluent from the secondary stage out of holding basins, whereupon it enters the advanced tertiary treatment plant.
Ozone is added for disinfection, to reduce colour and odour, and to optimise the rest of the treatment process.
Biological filters containing helpful bacteria biodegrade the organic matter and reduce ammonia, oil and grease, foam, litter and solids.
- Step4: More disinfection using ozone, which is generated on-site from oxygen.
- Step5: Exposure to ultraviolet light for further disinfection.
Treated water enters two large chlorine contact basins, where chlorine is added as part of the disinfection process. The basins also feed the treated water to the outfall pump station.
Tertiary treated water is transferred to the outfall pump station where some is recycled. The remainder is discharged to the ocean under strict EPA Victoria licence requirements.
The treated water is then recycled or discharged to the marine environment under strict EPA licence requirements.
Sewerage Treatment Process
Kinkajou : Let’s talk about some green recycling technologies. Technologies I am interested in include bioremediation, technologies for Air purification and reduction of pollution, and destruction of waste such as sewerage.
Kinkajou : Air purification something many of us do not consider as the time for recycling. Many people are not even aware that some common indoor plants can remove organic and other pollutants from indoor air. The plants absorb the chemicals. The cells in the plant metabolise these chemicals.
Well-known plants which may have a role in air purification include:
- Aloe Vera
- Peace Lily
Peace Lilly cleaning the air
This beautiful, low maintenance flowering plant reduces toxin levels in the air. The Peace Lily topped NASA’s list for removing formaldehyde, benzene and trichloroethylene from the air.
- Bamboo Palm
this plant is great at clearing out benzene and trichloroethylene. A high transpiration rate means that Bamboo Palms pump moisture back into indoor atmospheres.
- English Ivy
According to NASA, this is the number one houseplant to grow indoors due to its incredible air filtering qualities. This plant may also reduce airborne faecal-matter particles!
- Snake plant
This plant releases oxygen during the night rather than the day, and one in the bedroom may help you sleep better. Snake plants don’t need much light or water for survival, so they’re a perfect fit for any dim corners that need to be brought to life.
- Gerbera "Daisy"
Extremely effective at removing chemical vapours in the air, this flowering plant can filter out trichloroethylene and benzene – making it perfect for a well-lit laundry or bedroom. What’s more – the Gerbera Daisy has long-lasting flowers that will bloom throughout winter!
Kinkajou : I can see that if human beings are ever to go into space, we need to plan natural bio factories that can help detoxify and improve the environment, independent of chemical reprocessing systems. In fact this Biotech is nano-biotech, developed by evolution over millions of years.
Tell us about the Status of Recycling Technology and its future market
Recycling Tech Market Factors
Erasmus : Pollution feeds into the recycling issue. Waste needs to be recycled. If recycled, waste stops polluting the environment. Perhaps we can’t recycle air pollutants, but we can reduce waste and its disposal into the environment. Some forms of waste such as hazardous chemical or nuclear waste is something that no society can afford not to secure recycle. Green House gases are waste or air pollutants of a sort.
Kinkajou : I think we are becoming more aware of our need to consider “waste” as being part of the recycling equation. Even wastes such as greenhouse gases carry some danger with their generation. As a society we need to work towards lessening our footprint on the planet.
If as Dr Xxxxx says, we do ever reach that magic figure of 70 billion people, we will need to be ever mindful of the footprint that human society has on the planet. The biosphere is limited.
To cope with the demands made on it by large numbers of people, the earth demands that humanity take up the chalice of being responsible for the management of water and resources.
Goo : Recycling is one of those issues were an economic imperative exists. We can only do what is economic or affordable to do. Of course how we measure this depends on our way of looking at the world. We have talked about many models of assessing the desirability of recycling.
Certainly, if the human race wishes to go into space, humanity will have to learn to recycle much much better. So much of our technology and societies based on the ability to replace things.
But a spaceship is the ultimate closed system. I do not think we are up to the task of designing systems to run with minimal repairs for periods of time such as up to hundred years.
Humanity has some buildings and some bridges surviving for this time, but there are very few working technologies which can make such a claim to longevity.
There are many social issues to recycling. Much of what can be done depends on what is agreed that needs to be done.
The suggestion that humanity may one day reach 70 billion souls on a single planet is frightening. Yet I can see that some of the technology we have discussed may well allow us to reach this figure without increasing the footprint of humanity on the planet.
I think humanity needs to accept the ultimate responsibility for the management of this planet. It is capable of being a force for much good. Its future depends on acting responsibly in managing its finite resources. Recycling as part of the future.