Issue 03/2016

Materials
Using biomass side-streams
for bioplastics in New Zealand
Biomass side streams are finding their way into
novel bioplastic composites in New Zealand
thanks to local industries and innovative and imaginative
scientists at Scion.
Biomass side-streams and bioplastic applications are
often mentioned in the context of circular economies
and bioeconomy, two concepts that enable and complete
each other. With circular economies promoting the
maintenance of resources at their highest possible level
of value at all times, waste becomes a resource fuelling
economic growth. The bioeconomy becomes a perfect
illustration of circularity when it builds on sustainably
sourced and produced biomass for fuel, chemicals and
other materials by using waste streams to underpin
development of new sustainable products.
A key element to both systems is considering the
full potential of waste. Scion, a New Zealand research
institute that concentrates on biomass production
and utilisation, is continuously seeking new ways to
convert primary industry side-streams into value-added
products, contributing to the circular economy and
the bioeconomy. The following case studies from New
Zealand demonstrate how biomass side-streams can be
successfully incorporated into bioplastic materials and
products.
Pomace has promise
The fibrous mass that remains after the first step
in winemaking, pressing the grapes, is called grape
pomace or marc. Five tonnes of grapes produce one
tonne of pomace. In 2015, the New Zealand grape
harvest was 326,000 tonnes leaving the wine industry
with around 60,000 tonnes of pomace to dispose of.
Pomace is generally composted, but Scion has found
one more use for this resource before it regenerates
carbon back into the environment.
Many wine makers have a strong desire to use
sustainable practices to ensure the longevity of their
industry. Scion discussed possible applications for
using biodegradable products with a local winemaker.
The polystyrene clips used to secure the netting that
protects the ripening grapes from birds were identified
as an ideal candidate for replacement. Millions of the
clips are used every year. When the nets are removed,
the clips break easily and litter the ground, where they
persist for years.
In response to this, scientists at Scion have produced
bio-clips from rigid films containing red grape pomace
and biodegradable polymers. The fibre from the skins
both stiffens the clips and makes them easier to break.
Four different bio-formulations were trialled at Villa
Maria vineyards in Hawkes Bay during the run up to the
2016 harvest. None of the clips holding the nets gave way
prematurely and the clips were all brittle enough to break
when the nets were removed. The next step is to monitor
the biodegradation of the clips in the vineyard.
Scion is also working on other applications for grape
pomace in biocomposites such as spray guards to protect
newly planted vines.
A future for dairy farm effluent
Between 10 and 20 % of a dairy cow’s poo production
is deposited in the area of the milking shed. A farmer
milking an average herd of 420 cows deals with more
than 200 kg of solids and 20,000 litres of effluent a day.
Storing and managing dairy farm effluent (DFE) is a
significant cost. DFE is usually contained in ponds and
treated. A proportion can be used as fertiliser, although
the amount has to be carefully managed to prevent
contaminating waterways and ground water and preserve
soil structure. The problem of managing and disposing
of DFE is likely to worsen as New Zealand’s dairy herd
increases and farming becomes more intensive and
closer to international practice.
In 2015, the national herd of just over five million
milking cows produced around 2,800 tonnes of DFE solids
daily. The solids contain a high proportion of cellulosic
fibres. Applying circular economy thinking, this waste
by-product of milk production – biomass processed
(digested) via cow – is a fibre resource with potential for
use in bioplastics.
A grape pomace biocomposite clip holding netting to protect
ripening grapes in place.
32 bioplastics MAGAZINE [03/16] Vol. 11