Energy-from-waste

Energy-from-waste development in Cornwall

SITA Cornwall works in partnership with Cornwall Council to manage the household waste produced in the county each year – the aim being to first minimise the amount of waste created, then reuse and recycle wherever possible in order to reduce the amount of residual waste that is sent to landfill.

Despite these efforts, there is still a significant amount of household waste which is not recycled and has traditionally been sent to landfill. However, with landfill tax placing an increasing financial burden on Cornwall’s taxpayers and suitable landfill sites becoming scarce, SITA Cornwall sought an alternative solution for managing the county’s waste.

Cornwall Energy Recovery Centre

The Cornwall Energy Recovery Centre (CERC) near St Dennis uses waste that is left after recycling as fuel to generate sustainable energy in the form of electricity. This means the council avoids high landfill charges, and helps reduce our dependency on fossil fuels.

In addition, the on-site recycling facility uses the ash produced by the process to make secondary aggregate products for road-building and construction, for example.

The facility includes a purpose-built visitor centre with interactive displays and activities that explain the importance of reducing, reusing, recycling and recovering value from waste.

Emissions

The CERC has been designed to satisfy the stringent standards of the European Union’s Industrial Emissions Directive.

The gases from the combustion process go through a multi stage clean-up process. What comes out of the chimney is largely steam, oxygen, nitrogen and carbon dioxide with tiny amounts of pollutants. These are well within the strict levels set by the Environment Agency in the facility’s environmental permit.

Monitors at the base of the chimney continuously record emission levels. You can see the current monitoring information below.

What are the emissions?

Particles
Particles, also called particulates, are formed during the combustion process. These are captured in bag filters and form part of the Air Pollution Control Residue (APCR) which is sent for disposal off site in sealed containers.

Carbon monoxide and VOCs as Total Organic Carbon
High temperatures, a good mix of waste and sufficient air are all needed to achieve complete combustion and limit the formation of carbon monoxide and total organic carbon.

The temperature of the furnace is carefully controlled and additional burners can be used to bring up the temperature if it starts to drop.

A good mix of waste is achieved, initially using the grab in the bunker, but also on the moving grate in the furnace which keeps the waste moving throughout combustion.

The air flow into the furnace is controlled using fans alongside and underneath the grate.

Sulphur dioxide, hydrogen chloride and hydrogen fluoride
Many of the things we throw away, including batteries and plastics, contain either sulphur, chlorine or fluorine. These are released during combustion and react with the air to form sulphur dioxide, hydrogen chloride and hydrogen fluoride.

We use hydrated lime and lime slurry to neutralise these gases and convert them into a solid which can be captured in the bag filters. This excess lime, particulates, salts and carbon dust make up the Air Pollution Control Residue, which is sent for disposal off site in sealed containers.

Oxides of nitrogen and ammonia
Whenever anything is burnt in air, oxides of nitrogen are formed. This is because the air we breathe is made up of nitrogen (78%) and oxygen (21%) which combine during combustion. Nitrogen dioxide and nitrogen monoxide are known as oxides of nitrogen or NOx.

To control these in the combustion process, we inject ammonia into the furnace, which reacts with the oxides of nitrogen to produce nitrogen and water.

Emissions monitoring and energy generation

Click here to download the latest emissions monitoring and energy generation results for the facility.

Bottom ash recycling

The bottom ash left after the waste has been burnt is cooled and carried by conveyor to an on-site recycling facility.  Metals are separated for recycling and the remaining ash is processed to make secondary aggregate products for use in road building and construction activities.

Bottom ash is a non-hazardous material and is tested regularly to ensure this, in accordance with the Environmental Services Association Sampling and Testing Protocol. Each month, a random sample is taken from the bottom ash and tested at an independent UKAS-accredited lab.  The results of this testing are reported to the Environment Agency in line with the requirements of the facility’s Environmental Permit.  The facility entered operations in late March 2017 and testing began in April 2017 – to date, all samples have tested as non-hazardous.

The test results for the October 2017 sample were non-hazardous.

Communication

SITA Cornwall remains committed to communicating openly and effectively with local residents and community representatives.

The CERC Community Forum, with members drawn from the Clay Country, meet regularly to receive updates and raise any issues relating to the CERC that may impact local communities. View the minutes here.

Contact us

If you have any questions, concerns or comments regarding the CERC, please call us on 08456 300 300.

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