02 | 2008

Opinion
decisions are made, assumptions should be set aside and
the life cycle of each alternative choice should be evaluated.
Defra funded a study, commissioned by the NNFCC and
carried out by Imperial College London, to examine the issues.
The study looked at the life cycles of four different
bags: a typical HDPE carrier bag, used as the reference product;
an oxo-degradable lightweight bag made from HDPE
with an added catalyst that makes it breakdown in sunlight;
a biodegradable MaterBi bag; and a prototype biodegradable
bag made from formulations of NatureWorks PLA and BASF
Ecoflex. The results showed that waste management scenarios
considered in an LCA greatly influence the outcome.
The option with the least environmental impacts in the investigation
was actually HDPE carrier bags disposed of via an efficient
recycling process with 90% avoided product. However,
such efficient recycling is currently not a realistic scenario.
The next best option is the use of Mater-Bi bags, preferably
disposed of by incineration which gives a slightly better environmental
profile than composting or landfill. Oxo-degradable
bags disposed of via incineration or landfill are the next
best options followed by the heavier HDPE bags disposed of
via incineration or landfill.
The prototype biodegradable bag initially presented the
worst environmental profile, but a ‘bad’ LCA result doesn’t
mean the product is ‘bad’; it just shows where there is room
for improvement. These bags are relatively heavy, but the
LCA demonstrates the environmental benefits of reducing
their mass. A lighter bag improves the environmental profile
down to a level at which they perform better than HDPE bags
and only slightly worse than the Mater-Bi bags, indicating
that further development of these bags offers much potential
for environmental improvement. So which is the best bag?
There isn’t a clear ‘winner’, so the answer depends on how
you view the alternative waste disposal methods. The takehome
message is that the LCA has provided useful information,
but hasn’t relieved us from making difficult decisions.
LCAs can be worth the time and effort that is put into them
as long as you bear in mind these key points:
• (1) It’s just a tool!
• (2) It is a snapshot of constantly changing reality.
• (3 ) LCA is not the end of a process but the beginning.
• (4) LCA can help to identify the environmental hotspots in
your production process.
• (5) Comparing products can be very difficult.
LCAs have shown that bioplastics can have significantly
lower environmental impacts than petrochemical-based
plastics; however, the issues of scale-up, functionality and
evolving waste streams must be considered to maximise
market penetration of sustainable products. Bioplastics
manufacturers should accept that LCA is part of your toolkit,
rather than the definitive solution.
www.nnfcc.co.uk
Article contributed by
Dr. John Williams, Technology Transfer
Manager, and Dr. Louise Dommett,
Science and Technology Writer
The National Non-Food Crops Centre,
York, UK
bioplastics MAGAZINE [02/08] Vol. 3 37