Viridor Waste builds major new plant at Beddington

The first phase of a massive new composting plant is currently being built at the Beddington, Farmlands Landfill Site, near Croydon in Surrey, for Viridor Waste (Thames) Ltd. Steve Last, Technical Manager, and Martin Carville, Principal Civil Engineer and Technical Manager, Enviros Consulting report of this major scheme

Compost from a new composting facility, currently under construction at Viridor Waste (Thames) Ltd's Beddington Farmlands Landfill Site, will soon be available, as work progresses on this, one of the first, DEFRA grant-aided composting plants. The preliminary proposed programme is to build the plant in three phases, two for composting green waste materials only, the third for composting MSW. The first phase is estimated to cost £1.6 million.

New Waste Technology Funding has enabled a 15,000 tonne per annum green waste composting facility to be constructed for Viridor Waste (Thames) Ltd at its waste facility at Beddington Farmlands, near Croydon. The plant has been designed as a forced-air, in-vessel system followed by windrow maturation to produce a high quality compost product.

The facility will accept green waste from local authorities in the immediate area. On arrival at the facility, the green wastes will be shredded using a dedicated shredder, water being applied during the shredding process to provide adequate moisture content for the composting process. After shredding in a covered shredder bay, the material will be placed in one of six composting tunnels using a wheeled loader. Other tunnels are provided for the odour suppression biofilters.

In-vessel process

The in-vessel process will compost the green waste over a pre-determined period, oxygen being supplied using 37kW blowers through a network of pipes cast into the concrete base slab of each tunnel. Control over the air flow rate will be by frequency inverters linked into volumetric airflow meters, with the primary movement being recirculation of air through the composting mass.

Supplementary air will be provided to maintain control over both oxygen concentration and temperature.

The relative air flow rates are controlled to ensure that the air space above the composting mass is slightly negative with respect to atmosphere, thereby ensuring that there will be little likelihood of unwanted release of malodorous air from the composting mass.

Waste air from the composting mass will be transferred to a biofilter via a dedicated blower, again through a network of pipes cast into the filter's base slab. The biofilter media is supported over an open air space (plenum) to ensure that a uniform volumetric loading on the underside of the media is achieved. After the air passes through the media, it will be released to atmosphere.

The in-vessel system design is fully automated, being controlled by a bespoke software package developed specifically for this process. The composted material will be removed from the tunnels and placed in "windrows" in a maturation area, for a predetermined period before being screened, ready for delivery to end-users.

Enviros design

The project is being built to a detailed design by the Enviros compost team, and the construction stage is also being supervised by Enviros Consulting. The main contractor is Ascot Environmental, operating from that company's Basildon office. The contract works are running to programme with the plant commissioning due to take place during June and July 2004.



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