Northacre Resource Recovery Centre Mechanical Biological Treatment (MBT)
Northacre Resource Recovery Centre Mechanical Biological Treatment
What is this site?
The permit for Northacre Resouce Centre LP3491EE was issued to Hills Waste Solutions Limited by the Environment Agency in 2009.
The site is located on Stephenson Road (NGR 8565 5190) in an industrial area to the north of Westbury.
The facility accepts residual municipal solid waste (MSW) predominantly from household waste collections.
The wastes are those which have not been removed or segregated previously for recycling prior to disposal and arrives as black bag waste.
The Mechanical Biological Treatment (MBT) process carried out at the facility, produces a solid recovered fuel (SRF) / refuse derived fuel (RDF) and helps reduce the amount of biodegradable waste being landfilled. It also separates out other recyclable materials, for instance ferrous metals and aluminium.
The plant consists of 4 main areas:
1. Reception and pre-treatment
MSW is delivered on refuse collection vehicles and deposited into the reception pits. The material is moved from the reception pit by automatic cranes/conveyors and through a drum screener that creates two waste streams; oversized material (anything over 220 mm), and undersized materials (primarily the bio-degradable fraction).
Oversized material is collected in a dedicated storage bay from where it is sent directly to the SRF/RDF refining plant. This stream is composed of biologically inactive material (typically plastic, paper and card) and is not suitable for biological treatment.
Undersized material, the biologically active fraction, is collected in a second dedicated storage bay before being placed in windrows (sectors) within the bio-drying hall, by automated cranes.
2. Bio stabilisation (Bio-drying hall)
An automated crane moves material from the undersized storage area into the main bio-drying hall, creating windrows of approximately 3 to 5 metres in height. Air movement/extraction through an underfloor area of the bio-drying hall assists with the drying process and stabilisation of the material by removing moisture in the air flow. It also acts to prevent the windrows from overheating by removing heat from the body of the waste.
Each windrow is managed separately to maximise bio-stabilisation. Air is drawn through the material to promote aerobic decomposition and oxidation of the organic content for a period of up to 15 days. During these 15 days, the windrows remain static. Once a windrow has completed its 15-day cycle, the stabilised material is sent to the refinement area. The windrows are filled with new waste and emptied of stabilised decomposed waste on a rotational basis. The time that waste is held in the bio-drying hall is monitored through the control system. The temperature and air flow within each windrow is monitored and air flows can be adjusted to optimise the drying process and/or heat removal.
3. Mechanical refining (Refinement)
Through the refinement area, material which is unsuitable for SRF production is removed by the equipment below:
• Primary shredder
• Drum screener (20 mm mesh)
• Air drum separator
• Magnetic belt
• Secondary shredder (SRF production only, not used for RDF)
• Eddy current separator
• Conveyors
• Chutes
• Dust extraction system
4. Baling, wrapping and storage (Warehouse and despatch)
The SRF/RDF material generated by the mechanical refining process enters the warehouse for baling and wrapping. The SRF/RDF, once baled and wrapped, is stored in the warehouse in preparation for loading onto enclosed trailers and transfer to Energy from Waste (EfW) facilities.
The facility accepts up to 90,000 tonnes of waste per annum.
What activities are covered by the environmental permit?
The permit seeks to minimises the risk of pollution to the environment , including those arising from site operations, maintenance, accidents, incidents, non-conformances.
A statutory permit review was undertaken by the Environment Agency in 2020.
The permit includes requirements for the:
-Types of acceptable waste,
-Techniques being used to treat the wastes
-Standard of the infrastructure used across the site
-Permittable emissions from the site.
-Reporting requirements
How do we regulate this site and check for compliance?
In line with the permit conditions set we will undertake regular visits of the site to ensure compliance with conditions of the permit.
We will review the operator’s documents / data submissions
Where raised levels of odour reports have been made by the public, we will increase the frequency of visits to establish the effects of the activity on the area.