Emissions Monitoring

Energy from Waste (EfW) facilities such as Allerton Waste Recovery Park (AWRP) are strictly regulated.

Like all Energy from Waste plants, AWRP is required to comply with the EU Industrial Emissions Directive (IED); this imposes strict emission limits for all industrial processes including Energy from Waste facilities.

All emissions are continually monitored and regulated by the Environment Agency (EA). In addition to continuous emissions monitoring, the EA carries out regular independent checks.

We use a variety of control and treatment processes to ensure that the gases created when waste is burned are cleaned and filtered.

Preventing pollution

The Mechanical Treatment (MT) plant extracts recyclable materials such as plastics and metals as well as organic materials. As well as enabling us to send these items on for recycling, it also ensures that waste is mixed; this is helpful in providing a consistent fuel for the Energy from Waste (EfW) process and maximises the efficiency of the Energy from Waste process.

Controlled burning

Keeping temperatures above 850°C for at least two seconds during the combustion process ensures that dioxins and furans are destroyed in the EfW boiler and are not released into the atmosphere. 
But we also keep the temperature below 1300°C and control oxygen levels to reduce the levels of nitrogen oxide produced.

Neutralising gases

As well as controlling the combustion process, urea, hydrated lime and activated carbon are injected into the flue gas to neutralise various components.

• Urea is injected to break down the nitrogen oxides which are produced during good combustion and convert them to nitrogen and water.
• Hydrated lime is injected to neutralize oxides of sulphur and hydrogen chloride and reduce acidity.
• Activated carbon is also injected to trap heavy metals and any remaining dioxins.

Filtration is key

A bag filter system is used to collect dust and particulates from the gases.

To ensure these controls are operating correctly, AWRP, like other similar facilities in the UK, uses a continuous emissions monitoring system.

Further information about the emissions we monitor:

Dust (Particulate matter)

What is it?
Particulate matter, or particles is the term used to describe tiny particles in the air which are made up of a mixture of soot, organic and inorganic materials. These are smaller than or equal to 10 microns – or 100th of a millimetre in diameter.

How is these released?
There are many man-made and natural sources of Particulates including road transport, industry, volcanoes and dust storms.

How does AWRP control this?
Gases created during the combustion process are filtered through a bag filter system, this features 350 ‘bags’ which trap the fine dust.

Total Organic Carbon (TOC)

What is it?
TOC is part of a large group of liquids and gases known as volatile organic compounds (VOC). These are gaseous and can vaporise at room temperature. They can also react with other gases such as Nitric Oxide to form ozone at low atmospheric levels; high concentrations of this can be harmful to human health.

How is it released?
Paints, natural gas, petrol, road transport and industrial processes are the major sources of these compounds; however some are also produced by natural biological processes.
Organic chemicals are widely used as ingredients in household products. Paints, varnishes and wax all contain organic solvents, as do many cleaning, disinfecting, cosmetic, degreasing and hobby products. Fuels are made up of organic chemicals. All of these products can release organic compounds while you are using them, and, to some degree, when they are stored.

How does AWRP control this?
By ensuring that waste is burned for two seconds at 850°C.

Carbon Monoxide

What is it?
This can occur naturally and is also manufactured during industrial processes.  It is a colourless, odourless poisonous gas.

How is it released?
It is released by vehicle exhausts and small amounts are released through the burning of fossil fuels in power stations and Energy from Waste facilities.

How does AWRP control this?
Our combustion controls ensure that waste is burned at 850°C for two seconds - by getting the right combination of heat and oxygen we reduce carbon monoxide concentrations.

Hydrogen Chloride

What is it?
This occurs naturally and can be manufactured. It is a colourless gas is acidic and corrosive and has a strong pungent smell.

How is it released?
The main sources of this are coal-fired power stations; small amounts are released from Energy from Waste facilities.

How does AWRP control this?
Our flue gas cleaning system injects hydrated lime and activated carbon to eliminate hydrogen chloride.

Oxides of Nitrogen

What is it?
Nitrogen Oxides or NOx  is a combination of two gases – nitric oxide (NO) and nitrogen dioxide (NO2). NO is colourless and odourless while NO2 is reddish-brown and pungent. These are classed as greenhouse gases.

How it is released?
NOx is mainly released through the burning of fuel including vehicles, biomass burning and some production processes. It can be naturally released through lightening and natural fires.

How does AWRP control it?
As well as being minimised by the controlled combustion process, urea is also injected into the Energy from Waste boiler to control this.

Sulphur Dioxide

What is it?
This is a colourless gas with a strong odour; it can occur naturally or be created.

How is it released?
This is produced by burning coal and oil, typically by power stations and oil refineries. It is also created by any open fire and can also be released naturally from forest fires and volcanoes.

How does AWRP control it?
Hydrated lime and activated carbon are injected into the flue gas network to neutralise this.

Dioxins and Furans

What are they?
These are related types of complex chemicals containing chlorine. There are several hundred dioxin substances, they are crystalline when solid and dissolve in solvents, fats and oils but not in water.

How are they released?
These can be released as by-products from the burning of fuels, including waste. Some industrial processes including metal processing and paper manufacturing also create these. They are found in cigarette smoke and are released naturally from volcanoes and forest fires.

How does AWRP control these?
We minimise the formation of these by burning waste for at least two seconds at 850°C. Any remaining small amounts are absorbed into the activated carbon that is injected into the flue gas network of pipes.
The reaction products are a dry solid material called Air Pollution Control Residue (APCR) which is then separated by means of the fabric filter from the gas stream and disposed of off-site at a suitably permitted treatment facility.