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Waste in the Park
Already established in Istanbul, a compost turning
machine is going to be installed as part of Cambridgeshire
County Council's £730m waste contract. Tom Freyberg
went to site to find out more about a facility that will also
incorporate a £41m MBT plant.
In APRIL this year Donarbon Waste Management of Waterbeach
established itself on the waste management map by winning
Cambridgeshire County Council's £730 million, 28 year
PFI contract.
Up against the likes of Shanks and the Waste Recycling Group
(WRG), it was a big result for Donarbon and the industry,
demonstrating that a small to medium sized company can beat
the larger players.
"Donarbon was basically in the right place at the right
time with the right proposal to win the contract," recalls
a modest Mark Shelton, waste promotions manager at Donarbon.
Set up in 1969 as part of the Dickerson Group, a sand, gravel
and aggregate extraction company, Donarbon was originally
set up to manage the filling of worked out quarries.
This was done through skip hire, collecting inert waste only
mostly construction and demolition waste and from small builders.
In 2002 the firm won its first major council contract with
the county council, for the landfilling of residual waste
and composting of kerbside collected garden waste from four
of the five districts: Cambridge City, South Cambridgeshire,
East Cambridgeshire and Fenland.
The centrepiece of Cambridgeshire's PFI contract is a £41
m mechanical biological treatment (MBT) plant, currently being
built by civil engineer firm, BAM Nuttall.
The plant is expected to handle 170,000 tonnes of waste per
year.
Currently being constructed on the Donarbon's waste management
park in Waterbeach, the 400 acre site has planning permission
for integrated waste management facilities. This, and the
fact that the company has worked hard on being a good neighbour
with all local councils and residents, has resulted in no
planning permission issues that have historically proven difficult
with other waste processing plants.
The company's waste management park is no stranger to waste.
Waterbeach has in the past dealt with construction, demolition
commercial and industrial wastes and since 2001 accepted green
waste for composting through an in vessel composting plant.
As principal contractor, Nuttall is responsible for managing
the supply chain, including Austrian based company, Kelag
Umwelttechnik, who will be providing the composting process
design and machinery (worth 35% of the contract value).
Initial works include the installation of 5,000 vibro stone
columns.
BAM Nuttall says the structure itself will consist of an
external galvanised steel frame with internal composite cladding
panels. The external frame design aims to protect the structural
members from the composting process.
"Black bag municipal solid waste (MSW) will be brought
to the reception hall of the facility," says Adam Bunce,
agent for BAM Nuttall. "Here, shredders will rip open
the bags where 63 different pieces of sorting equipment, including
ballistic and near infra red separators, will sort the materials
into different streams, including glass, ferrous and non ferrous
metals, stones and mixed plastics.
"Once the recyclable materials are separated and sent
off for reprocessing, the remaining organic material is mixed
with water and sent into the composting hall for processing."
This is where the piece de resistance plays its part. Known
as CTM technology (Compost Turning Machine), the system works
by using a giant water wheel type device that scoops the material
backwards, where a conveyor shifts it behind.
The turning machines run on railway tracks over a 32m gap.
Walking in the middle of one of the enormous composting bays
still under construction, it's impressive to imagine the giant
machine sliding back and forth, churning away.
According to the manufacturers, the system "automatically
turns and moves a table windrow while simultaneously homogenising,
loosening, aerating and irrigating the material within the
composting/ MBT building". When asked if the process
will capture any heat process, Bunce says due to the machinery
turning the material so often, it doesn't lend itself well
to having pipes under the floor to capture the heat.
After a seven week process, the finished product will have
75% of its biodegradability and 50% of its weight reduced.
Despite the material having obvious organic benefits, Shelton
points out that current regulations mean it won't be classed
as a compost.
"With the current regulations, it doesn't matter how
well the composting and sorting system works, the end product
won't be classed as a compost or achieve PAS 100 because it's
derived from MSW. We helped fund a research project at Cranfield
University into MBT output, and have employed a consultant
to look at end markets for this compost like material. We
have asked the Environment Agency what we can do with the
material, but they say that until they see the end product,
they are unable to comment."
End use options include the restoration of quarries and growing
energy crops. Donarbon has conducted a growing trial that
used waste derived compost to grow miscanthus or elephant
grass. It is expected that the compost like output of the
MBT will be similar to waste derived compost and could be
used to grow energy crops on restored landfills and quarries
owned by the Dickerson Group to help manufacture renewable
fuel.
The waste promotions manager is keen to point out how the
situation is different in other parts of Europe.
"The only other plant similar to this is in Istanbul,"
he says. "Legislation in Turkey is more relaxed so they
might use the product on roadside verges for example, whereas
this is obviously not allowed over here. Once there are a
few plants similar to this in the UK, the EA and Defra might
look at the quality of the output and call it a compost."
It is not just the architecture, construction and technology
that tick the box of modern design, but sustainable energy
methods too. The facility's sustainable drainage system (SUD)
will be located at the end of the composting bays.
Rain collected from the roof of the main reception hall is
saved in a 600 cubic metre tank, where it is used in the process.
A small cluster of solar panels, too, will be on the roof
of the visitor centre and will heat the water used in the
toilets.
Additional work to be carried out by BAM Nuttall will include
a three storey office building with conference rooms and an
education centre. This will be used to educate local schools
and the local community about the process employed at the
facility. A window from the education centre will even look
out on the processing hall giving visitors the chance to see
the whole process in action.
Being future proof is obviously a key design for the facility,
not only in terms of design and aesthetics, but how it operates
as well.
Shelton says the council is predicting that an additional
76,000 houses will be built in the county in the next 15 years.
In terms of generated recyclables and waste, that is the
equivalent of another district for us to deal with. The capacity
of the plant has allowed for this additional waste,"
he adds.
The facility will be operational in November 2009, when it
will go through a period of cold commissioning. Small amounts
of waste will be trialled over nine months before the plant
will be officially opened in mid 2010.
It is expected that the MBT plant, coupled with Donarbon's
in vessel composting facility and new recycling infrastructure
will mean 80% of Cambridgeshire's household waste is diverted
from landfill.
With the construction phase running to schedule, it is clear
the waste community is eagerly anticipating the opening of
Donarbon's facility. Not only will the plant demonstrate the
technology to the UK, it will show how high recycling rates
can go hand-in¬-hand with a waste treatment technology
and help reduce the amount of waste landfilled down to a minimum.
Article courtesy of Sustainable Solutions (December /
January 2009)
Further Info
Peter Bishop - Head of Public Relations & Corporate Communication
BAM Nuttall Limited
St James House, Knoll Road, Camberley,
Surrey GU15 3XW
Tel: 01276 63484
Fax: 01276 66060
peter.bishop@bamnuttall.co.uk
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