bioplasticsMAGAZINE_0902

Basics
Picture 6: Burl wood biofilter for exhaust air
After the composting phase the mature compost is screened
again, and different fractions with different average particle sizes
are sacked or otherwise packed for different purposes. In Moerdijk
from a first 40mm fraction heavy particles such as stones or
glass are gravimetrically separated. The rest is then once again
sieved to a fraction smaller than 15mm as a high quality compost
(picture 7) which is sold to farmers (80-90%) or garden owners
(10-20%) as soil conditioner, fertilizer or a substitute for peat.
The 15-40 mm fraction is sold to a special incineration plant in
Germany as ‘clean biomass for incineration’. This fraction may
even contain up to 3% plastic waste. The residual bigger plastic
waste pieces after screening are again collected and disposed
of to a waste incineration plant. Tim Brethouwer is happy that
in Moerdijk there is such an incineration plant right next door.
This saves the trouble of transporting the material. “Before we
could bring the ‘clean biomass’ to that special incineration plant
we recycled the 15-40mm fraction into the process to compost it
again for a further 3 weeks,” said Mr. Brethouwer.
When asked whether the operators of industrial composting
plants like or dislike biodegradable plastics in their incoming
feedstock Tim Brethouwer said: “We don’t have a problem
with bioplastics. We accept biodegradable plastics but we
don’t seize them”. Mr. Lammers said “We appreciate the use
of biodegradable bags for the collection of biowaste instead of
traditional plastic bags. If everybody would use this kind of bag
we would not no longer need manual sorting.” Dr. Hubert Seier,
technical controller of the plant in Dortmund added: “However,
I’d like to point out that we accept biodegradable plastic bags BUT
... ,” and he explained that educating the public is an important
subject. Mrs. Smith, let‘s say, puts a biodegradable bag, with her
kitchen waste, into the bio-bin and her neighbour watches her
from behind the curtain. Then the neighbour puts plastic bags
in the bio-bin, not caring whether they are biodegradable or not.
This must not happen.
Picture 7: This handful or high quality compost contains
more microorganisms than the number of people on earth
When talking about the different end of life options, Tim
Brethouwer points out that (at least in the Netherlands)
composting with costs of about 35 EUR/tonne is cheaper than
incineration where 100 EUR/ tonne have to be paid. The most
expensive solution is landfill. Here in addition to 85 EUR tax per
tonne an additional gate fee of 20-30 EUR has to be paid. And
from a CO 2
point of view he considers composting as the better
alternative as composting locks CO 2
in the soil and releases it to
the atmosphere only very slowly. About 10% of the CO 2
is still in
the soil after 100 years, he explains.
As one of the solutions with the best future prospects Tim
Brethouwer sees the combination of anaerobic digestion
(biogasification) and subsequent aerobic composting. Here three
products will be produced: biogas that can be converted into or
mixed with compressed natural gas (CNG) or liquefied petroleum
gas (LPG) a fuel that is very popular with a large number of Dutch
car owners. The second product is compost and the third is the
‘clean biomass for incineration’ mentioned above.
www.entsorgung-dortmund.de
www.essentmilieu.nl
36 bioplastics MAGAZINE [02/09] Vol. 4