What is a biopolymer?
Biopolymers are polymers
that are biodegradable. The input materials for the production of these polymers
may be either renewable (based on agricultural plant or animal products) or
synthetic. There are four main types of biopolymer based respectively on:
1. Starch
2. Sugar
3.Cellulose
4.Synthetic materials
Current and future developments in biodegradable polymers and renewable input materials focus relate mainly to the scaling-up of production and improvement of product properties. Larger scale production will increase availability and reduce prices.
Applications
Benefits
Towards sustainable products?
Further information/ credits
Polymers have properties that make them suitable for use in protecting products from moisture, increasing shelf-life and making products easier to dispense.
Every biopolymer has its own material-specific properties, e.g. barrier properties such as oxygen permeability. The barrier properties are relevant to the choice of biopolymers for the packaging of particular products. Bioplastics have very promising prospects for use in pesticide soil pins, for packaging in-flight catering products and for packaging dairy products.
1. Starch based polymers
Applications
Thermoplastic starch is unsuitable for packaging liquids. It can sustain only
brief contact with water. It has good oxygen barrier properties.
Sources
Starch is a natural polymer which occurs as granules in plant tissue, from
which it can easily be recovered in large quantities. It is obtained from
potatoes, maize, wheat and tapioca and similar sources. Starch can be modified
in such a way that it can be melted and deformed thermoplastically. The resulting
material is thus suitable for conventional plastic forming processes such
as injection moulding and extruding.
2.
Sugar based biopolymers
Applications
Polyalctides decompose harmlessly
in the human body and have therefore long been used for medical applications.
Examples include surgical implants which do not require operative removal. Until
recently, it was not feasible to use polylactides for packaging because of their
high price, around US$500 per kilogram.
Sources
• The starting material for Polyhydroxibutyrate is made from sucrose or
starch by a process of bacterial fermentation. Varying the nutrient composition
of the bacteria produces differences in the end product. This makes it possible
to tune the properties of the material, e.g. its moisture resistance. The polymer
can be formed by injection, extrusion, blowing and vacuum forming.
• Polylactides (lactic acid polymers)are made from lactic acid, which is in turn made from lactose (or milk sugar) obtained from sugar beet, potatoes, wheat, maize etc. Polylactides are water resistant and can be formed by injection moulding, blowing and vacuum forming.
3.
Cellulose based biopolymers
Applications
Familiar applications of cellophane
include packaging for CDS, confectionary and cigarettes. The material is gradually
falling out of favour, however, owing to its high price (about US$6 per kilogram).
Other cellulose polymer materials (e.g. cellulose ilm) have also been commercially
available for many years but are losing market share to newer polymers such
as polypropylene.
Sources
The use of cellulose for making packagin material such as cellophane is long
established. The material is transparent and has good folding properties. Whether
in the form of pure cellulose or of a nitrocellulose coating, the material is
wholly biodegradable and can be composted by existing waste processing plant.
4.
Synthetic based biopolymers
Applications
The relatively high price of biodegradable
polymers of synthetic substances, e.g. aliphatic aromatic copolyesters has prevented
them from reaching a large scale market. The best known application is for making
substrate mats.
Sources
Synthetic compounds derived from petroleum can also be a starting point for
biodegradable polymers, e.g. aliphatic aromatic copolyesters. These polymers
have technical properties resembling those of polyethylene (LDPE). Although
these polymers are produced from synthetic starting materials, they are fully
biodegradable and compostable.
Besides being available on a sustainable basis, biopolymers have several economic and environmental advantages. Biopolymers could also prove an asset to waste processing. For example, replacing the polyethylene used in coated papers by a biopolymer could help eliminate plastic scraps occurring in compost.
Consumers have a lively interest in biopolymers too. Conventional plastics are often seen as environmentally unfriendly. Sustainable plastics could therefore provide an image advantage.
The major advantage
of biodegradable packaging is that it can be composted. But the biodegradability
of raw materials does not necessarily mean that the product or package made
from them (e.g. coated paper) is itself compostable.
Biopolymers can also
have advantages for waste processing. Coated paper (with e.g. polyethylene)
is a major problem product for composting. Although such materials are usually
banned from inclusion in organic waste under separate collection schemes, some
of them usually end up nonetheless in the mix. The paper decomposes but small
scraps of plastic are left over in the compost. The adoption of biopolymers
for this purpose would solve the problem.
Widespread interest for biopolymers among consumers. Conventional plastics are environmentally unfriendly in the public perception. Sustainability can provide an image benefit. The environmental benefits of biodegradable packaging must be reflected in cost advantages, if large-scale applications are to become feasible. In the short term, it would be preferable to communicate the functional advantages of biodegradable packaging rather than its compostability.
Whether the use of biopolymers will contribute to a more sustainable society is a question that will have to be studied by a representative life cycle analysis (LCA) of each application and by comparison with existing applications. Representative LCAs are needed at material and product levels; they must make allowance for future developments in biopolymers and take account of all relevant environmental impacts associated with the complete product life cycle, including the depletion of raw materials, the agricultural use of fertilizers and pesticides, transportation, utilization and waste disposal.
Further information
Kiem Product Development
Support - Rapenburgerstraat 109 - 1011 VL Amsterdam
tel: +31 (0)20 6385678 - fax: +31 (0) 20 6384905
e-mail: kiemteam@knoware.nl
Nederlands Verpakkingscentrum
- P.O.Box 164 - 2800 AD Gouda
tel: +31 (0)182 512411- fax: +31 (0)182 512769
AgLink, business
constructors - P.O. Box 188 - 6700 AD Wageningen
tel: +31 (0)317 467667 fax: +31 (0)317 467660
e-mail: businessconstructors@aglink.nl
URL: www.agriholland.nl
Proterra International
Centre for Agro-Based Materials - P.O. Box 188 - 6700 AD Wageningen
tel: +31 (0)317 467660
e-mail: proterra@aglink.nl
This material issue, About Biopolymers, is based on the report ‘Tenminste houdbaar tot: verpakken met biopolymeren’ , compiled by ‘het Nederlands Verpakkingscentrum’, AgLink, KIEM and Proterra.
The project was subsidized by the Dutch Ministry of Economic Affairs.