 Huge potential for bioplastics
It almost sounds too good to be true - turning cow pats into
plastic. But the unlikely-looking liquid in the flask Dr Steven
Pratt holds is the key ingredient to an environmentally friendlier
drink bottle.
The murky mix of acids is produced by
fermenting bacteria taken from wastewater ponds and fed with a
glucose solution. A glucose solution is used in this laboratory
situation, but the bacteria will feed with equal efficiency on
dairy-farm effluent or other carbon-based wastewater.
It is
the renewable and biodegradable nature of such ingredients that give
the types of plastic produced from the acids the classification of
‘bio-plastics’.
A researcher in the Centre for Environmental
Technology and Engineering, Dr Pratt says the potential for
bioplastic production in New Zealand is huge.
“The waste
produced by our agricultural and pulp and paper industries is ideal,
and there is so much of it.”
He says plastics are a major
environmental problem as they are non-biodegradable and their
production from synthetic polymers consumes vast quantities of
non-renewable resources.
“By using cheap and renewable
sources there is a tremendous opportunity for biopolymer production
to be made economic. At the same time, the problems of wastewater
treatment and natural resource depletion are addressed.”
He
says some acids are better than others for the production of
bio-plastic. For example, acetic acid-based plastic is comparatively
brittle to that produced from other acids; it has been shown that
the inclusion of propionic acid produces polymer chains (the
building blocks of plastic) with the favourable characteristic of
malleability.
The task of producing one particular acid,
however, is complicated by the diversity of the constituents of raw
wastewater and effluent.
Part of Dr Pratt’s project looks at
controlling the fermentation procedure by adjusting factors such as
pH so that only one kind of acid is produced. His team of
postgraduate students are also focusing on a stage in the
fermentation process that is typically ignored.
“Fermentation
has been around for thousands of years, and the science of
fermentation has been understood for quite some time, but no-one has
really looked at what happens in transient stages.”
A
transient stage occurs when bacteria are shocked by the input of
food (in this case, carbon-based effluent) or when conditions such
as pH are altered. The micro-organisms react to these changes in
interesting ways before evening out and producing a consistent
volume of mixed acids.
“In this transient stage one type of
acid may be made in greater proportions, and other unknown or
unexpected compounds can also be made. Sometimes the most
interesting things are made when things go wrong.”
Created: 14 July, 2006 |
