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Bioplastics: an alternative with a future?
Plastics offer a broad spectrum of characteristics and applications and
are today a key material for many branches of industry. Global demand is
constantly growing and, with it, the expectations of the performance of
this group of materials.
In the last few years, rising crude oil prices have sharpened public
awareness of the finiteness of fossil resources and strengthened the
desire for greater climate protection and sustainability. And, within this
group of materials, interest has been stimulated in the special category of
bioplastics. As a complement and in some areas as an alternative to
conventional plastics, they appear to be a logical and necessary step for
a modern and forward-looking plastics industry. And they will also of
course have their place at K 2013 in Düsseldorf from 16 to 23 October.
Any discussion of the pros and cons, the future role and the market
potential of bioplastics makes little sense without prior clarification of the
meaning of the prefix “bio-”, says Prof. Dr.-Ing. Christian Bonten of the
Institute of Plastics Engineering at the University of Stuttgart, expressing
his reservations. For this is precisely where confusion arises.
One prefix, two meanings:
bio-degradable and bio-based plastics
Biodegradable plastics
Apart from small quantities of substances, biodegradable plastics consist
of biodegradable polymers and additives. Special bacteria and their
enzymes demonstrably convert biodegradable plastics into biomass, CO2
or methane, water and minerals as soon as the macromolecules have
been sufficiently fragmented by other degradation mechanisms. For a
plastic to be termed “compostable” in Europe, 90 per cent of it must
degrade in clearly defined conditions into fragments smaller than 2 mm
within 12 weeks. Only then can composting facilities operate costeffectively and without disruption. Before bioplastics can be allowed to
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enter the soil, proof must be additionally furnished that a certain heavy
metal concentration is not exceeded and that the soil’s fertility is not
restricted. Products conforming in Europe to EN 13432 may be marked
with the “seedling”, the European logo for compostability, on certification.
In the USA there is also a standard for proven compostability, which is
based essentially on the European standard.
Contrary to popular belief, biodegradable plastics are not necessarily
made from renewable resources and can also be derived from mineral
oil. Biodegradability therefore depends not on the raw material, but on
the plastic’s chemical structure. Examples of biodegradable polymers are
polylactides (PLA), polyhydroxyalkanoates (PHA), cellulose derivatives
and starch as well as mineral-oil-based polybutylene terephthalate
(PBAT) and polybutylene succinate (PBS). Non-biodegradable, on the
other hand, are polyethylene (PE), polypropylene (PP), polyethylene
terephthalate (PET) and polyamides (PA), for example.
The term “biodegradable” is also used in different ways. There are
conventional plastics containing only tiny quantities of biologically or
otherwise degradable substances. In suitable conditions, these merely
break down into smaller, barely visible constituents. However, they do
not fully metabolise and the fragments accumulate in the soil and food
chain over time.
Consequently, the very fact that a product is biodegradable does not
solve the problem of waste accumulation or litter in the countryside. Even
biodegradable materials take weeks to decompose in defined conditions
– microorganisms, temperature and moisture. In the absence of these
conditions, the plastic resists decomposition and biological degradation
can take several years.
Bio-based plastics
Bio-based plastics, on the other hand, are renewable resources derived
from nature. However, these are not necessarily biodegradable as well.
The adjective “bio-based” merely tells us that the carbon atoms in the
molecule chains come from today’s nature and are thus “bio”.
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Fossil hydrocarbons from mineral oil, natural gas and coal were also
once nature. They stem from plants and algae that lived about 500
million years ago. Through drying, certain geological processes and
bacterial decomposition in the absence of oxygen, they were converted
into “liquid fossils” or fossil hydrocarbons. The bacteria involved in these
prehistoric processes were not the same as those required for
biodegradation today (see above).
The combustion of fossil mineral oil, natural gas and coal releases the
carbon dioxide that the plants extracted from the atmosphere for their
own growth 500 million years ago. Today, however, it causes excessive
concentration in the atmosphere and the familiar associated problems.
We therefore have to distinguish between “bad” CO2 from the past and
“good” CO2 in the present. In research and industry, there is growing
interest in the use of renewable raw materials so as to reduce the
consumption of fossil hydrocarbons and thus to release less “historic”
CO2 into the environment.
At present, bio-based plastics are derived from different hydrocarbons
such as those found in sugar, starch, proteins, cellulose, lignin, bio-fats
and
oils.
Bio-based
polymers
include
polylactides
(PLA),
polyhydryoxybutyrate (PHB), cellulose derivatives (CA, CAB) and starch
derivatives as well as, for example, bio-polyethylene (PE). The latter is
derived entirely from Brazilian sugar cane, has the same properties as
conventional polyethylene, but is not biodegradable. The at least to some
extent bio-based but not biodegradable polymers also include naturalfibre-reinforced conventional plastics along with polyamides and
polyurethanes.
Bio-based plastics can undoubtedly make a valuable, albeit relatively
small contribution to improving the life-cycle assessment, as only a few
per cent of the world’s fossil resources are used for the production of
plastics. Over two thirds are still used for energy generation and
transport. From this it is obvious that bio-based plastics will hardly cause
food shortages – but more on this later.
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Bioplastics – global output
The
demand
for
plastics
is
steadily
growing.
For
2011,
the
manufacturers’ association PlasticsEurope put global polymer output at
280 million tonnes. Some 235 of these 280 million tonnes are used for
plastics materials, and bioplastics have not so far figured highly in this
survey.
Because of the high market growth, European Bioplastics is forecasting
world production capacity for bioplastics to reach roughly 5.8 million
tonnes by 2016. The study of the nova institute of March 2013 is even
more optimistic. According to its estimate, production capacity for biobased plastics will grow to over 8 million tonnes by 2016 and to roughly
12 million tonnes by 2020.
The production of plastics based on renewable raw materials has risen
very fast despite its low overall level compared to oil-based plastics.
According to the manufacturers’ association European Bioplastics,
biodegradable plastics accounted for several hundred thousand tonnes
and thus the lion’s share of total global capacity for bioplastics in 2009.
Since 2010, the growth rates for biodegradable plastics have been far
outstripped by those for bio-based plastics. According to association
forecasts and despite constant growth, they will account for only about a
seventh of overall bioplastics output by 2016. The far larger share of
bioplastics will then be bio-based but not biodegradable.
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Production capacity for biodegradable and bio-based plastics in 2011
with a forecast for 2016 (source: European Bioplastics; Hannover
University of Applied Sciences and Arts, IfBB – Institute for Bioplastics
and Biocomposites)
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Production capacity for various bioplastics in 2011 (source: European
Bioplastics; Hannover University of Applied Sciences and Arts, IfBB –
Institute for Bioplastics and Biocomposites)
There is a growing regional shift in the market shares of biopolymer
production. While Europe’s share of production capacity came to about
17 per cent in 2012, it will drop to about 5 per cent by the year 2016,
according to a study by the Institute for Bioplastics and Biocomposites
(IfBB). The IfBB expects Asia and South America to benefit – the latter
with a growth in production capacity from about 30 per cent in 2012 to
over 45 per cent in 2016.
Rising standards – bioplastics are no exception
For their growing technical applications, plastics have to meet
increasingly high standards. And bioplastics are no exception. As far as
reproducibility is concerned, they still have some catching-up to do, and
in terms of barrier properties, durability and compatibility with other
biopolymers and additives, there is still plenty of room for improvement.
However, bioplastics have come a long way from the often poorperforming pure biopolymers of the first generation. Ultimately, however,
the long-term success of bioplastics will depend on price, competitive
production capacity and reliability.
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Bioplastics and their applications today
Biodegradable plastics are usually employed in applications where
degradability proves to be particularly useful. This applies, for example,
in agriculture to mulch films and plant pots that do not have to be
collected and transported elsewhere after use, but metabolise on the
spot in the soil to form biomass. In private households, degradable
kitchen waste bags have conquered a market and can be composted
together with their contents.
Domestic/
Office
Furniture/-
Waste
near-domestic
supplies
furnishings
management
Watering cans,
Writing
Chairs
(Compostable)
vacuum cleaners,
implements,
waste bags and
drinking straws
correction
bin liners
products
rollers, rulers
Agriculture/
Catering
Construction
Electrical items
Agricultural films
Disposable
Tool handles,
Housings for
and nonwovens,
cutlery and
dowels, bio-PU
computer mice,
dispensers,
crockery,
insulation,
keyboards,
plant pots
waste bags
insulating
telephones,
materials,
mobile phones,
terrace surfaces,
cable insulation
gardening
and
landscaping
carpeting and
floorcoverings
Current applications of bioplastics (source: Hannover University of
Applied Sciences and Arts, IfBB – Institute for Bioplastics and
Biocomposites)
Bio-based plastics are now also found in consumer electronics and
automotive applications. The share of plastics in automotive engineering
has been steadily rising over the last few decades. The percentage of
bioplastics used here is now also growing. For its Sai hybrid car only
available in Japan, Toyota, for instance, has developed interior
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furnishings and equipment made of 80 per cent renewable raw materials,
as of model year 2011. This has been made possible by the use of bioPET, a plastic derived from sugar cane. It features temperature stability
suitable for car interiors, a low tendency to shrink and good mechanical
properties. Bio-PET’s carbon footprint is said to be far smaller than that
of
its mineral-oil-based conventional equivalents.
But PLA and
polyurethane (PU) foam based on soya are also found today in a vast
diversity of automotive components. Practically all car manufacturers
make use of bioplastics in their vehicles and are working towards
increasing their use.
Mulch films of biodegradable PBAT/PLA compound can be ploughed in
after the harvest and, unlike classical film, do not have to be first
collected and then disposed of (photo: BASF SE).
Transparent food film made of Bio-Flex® A 4100 CL / F 2201 CL / A 4100
CL (photo: FKuR)
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A paper cup coated with a film of plastic made of PBAT/PLA compound
does not go soggy and can be industrially composted (photo: BASF SE).
M440 ECO computer mouse housing made of Biograde® (source:
Fujitsu)
Are bioplastics the only good plastics?
In any blanket positive assessment of bio-based and biodegradable
plastics, it is often forgotten that energy from fossil fuels is also used in
their production – be it in the sowing of crops, harvesting, transport,
fermentation etc. It is therefore always essential to consider a product’s
entire life-cycle, because only then is it possible to conduct scientifically
sound life-cycle assessment comparisons and arrive at a well-founded
conclusion about a product’s sustainability.
Controversy over competition for agricultural acreage
Whether agricultural land should be used for anything other than the
production of food is a controversial issue. Here, again, it is worth taking
a more discriminating look. Prof. Dr.-Ing. Christian Bonten of the Institute
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of Plastics Engineering at the University of Stuttgart believes fears that
food shortages could arise due to the use of carbohydrates for bioplastics
to be unfounded. “The fact that the world’s energy needs cannot be met
with carbon sources of plant origin is confused with the far lower demand
for carbohydrates for the production of plastics,” says Bonten. According
to European Plastics, only 0.05 per cent of agricultural acreage in the
European Union would have been required in 2011 to satisfy total global
demand for bioplastics. In addition, for the production of bioplastics, it is
already possible in some areas to use wastes from the farming industry.
To prevent competition arising in the medium and long term, this raw
materials avenue must be developed further. Similar views are
expressed by Kristy-Barbara Lange, Head of Communication at
European Plastics, in an interview with Messe Düsseldorf in May 2012:
“Intensive research and development are taking place in the bio-refinery
sector to make it possible to tap second-generation raw materials such
as cereal straw, maize straw and other cellulose-based materials as
potential sources.” As soon as these are established, Lange continues, a
stream of fermentable sugars based on non-food cultivated plants will be
available for energy, chemicals and polymers. As a result, there would be
even less grounds for potential conflict over land use for food and raw
materials.
Finally, it can be said that nothing can stop the advance of bioplastics,
bio-based or biodegradable. In many areas bioplastics are already a
genuine alternative to conventional plastics and the view that they are not
(yet) competitive can no longer be sustained. However, a panacea for all
environmental problems they are not. Furthermore, the unqualified
portrayal of bioplastics as being totally carbon-neutral is at the present
time extremely premature. But they do pave the way into the post-oil era.
Whoever wishes to find out about the prospects for and potential of
bioplastics
along
with
the
latest
developments
and
innovative
applications will have plenty of opportunities to do so at the exhibitors’
stands at K 2013. The world’s most important trade fair for the plastics
and rubber industry is taking place this year in Düsseldorf from 16 to 23
October.
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In addition, Bioplastics Business Breakfasts, brief seminars on selected
industry topics, will be taking place from 17 to 19 October, daily from 8 to
12 h.
August 2013
Contact
Press Office K 2013
Eva Rugenstein/Desislava Angelova
Tel. +49-211-4560 240
Fax +49-211-4560 8548
Email: [email protected]
Email: [email protected]
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