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Environmental Metrics and Performance

We manage all the aspects of our environmental performance in accordance with our Environmental Management System (EMS) framework, which addresses environmental risk and regulatory compliance management processes.

Air Emissions

Combustion of fuels to generate electric power results in the release of both conventional and greenhouse gas (GHG) emissions. Depending on the fuels used to generate power, these conventional air emissions may consist of sulphur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM) and mercury (Hg). The combustion of fuels results in the direct emission of Scope 1 Green House Gases (GHGs), primarily carbon dioxide (CO2).

Air emission levels and intensities depend on many factors, including generation diversity and efficiency, demand for electricity, weather, fuel availability and prices, and emission controls deployed. We account for all emissions at all thermal power plants, and declare these in line with UK regulations.

We are continuously researching ways to improve power generation efficiency and reduce emissions. For example:

Industrial Emissions Directive

The Industrial Emissions Directive (IED) is a European Union directive which applies to existing plants from 1 January 2016 and supersedes the existing Large Combustion Plant Directive, further reducing emissions of nitrogen oxides, sulphur dioxide and particulates. Kilroot Power has opted into the Transitional National Plan and complies with the Emission Limit Values (ELV) which has required installing new equipment to improve emissions performance.

Ballylumford B Station Upgrade

AES won a tender from the System Operator for Northern Ireland (SONI) to provide additional capacity from 2016-18, with an optional two year extension. In order to meet strict environmental limits, Ballylumford B Station has been fitted with significant emissions reduction technology to extend the life of our natural gas boilers. New nozzle designs and recirculation of flue gases have been incorporated into the units to help stop the formation of NOx. Ballylumford is the only gas plant of its age in the UK to meet these environmental standards. By keeping these machines available we have helped secure the supply of electricity in the region until 2018 and beyond.

Heat rate improvements

Heat Rate is an industry standard performance measure defined by the amount of fuel consumed to provide 1 kWh of electricity (or 1 unit on a domestic/commercial electricity meter). Our UK & Ireland businesses carry out ongoing performance monitoring to identify any improvements that can be made to ensure we generate electricity as efficiently and cost effectively as possible. Our plants are audited as part of the AES Heat Rate Assessment Programme, which recommends actions to drive improvements. The assessment teams consist of members from a wide range of generating technologies, which helps spread innovative solutions within the company.

Energy Saving Opportunities Scheme

In 2015, our businesses participated in the Energy Saving Opportunities Scheme (ESOS), which aims to promote energy conservation across all aspects of our operations including our electrical generation processes, building management and vehicle usage. We have used external expertise to draw on knowledge from other industries to find common solutions.

Flue Gas Desulphurisation

In 2007, Flue Gas Desulphurisation (FGD) plants were fitted to our coal generation units to reduce the emission of Sulphur Oxides (SOx) to the atmosphere by using cooling water that has already passed through the stations condensing circuit. Kilroot also incorporates a filter system that ensures any metals such as mercury and vanadium are safely removed from the flue gas.


Water availability is a critical input for the electric power industry. At our generating stations, water is predominantly used for the steam cooling process at our thermal plants.

In order to minimise our environmental impact, our plants are designed to reuse as much of the water and steam in the generation process as possible. Water that has been heated and converted to steam is cooled back to liquid so that it can be used over and over again. We have systems in place to ensure we meet the highest quality standards in terms of water management and control of waste water on our sites.

Coal Combustion Products (CCPs) generation, recycle and reuse

Coal combustion products (CCPs) include bottom ash, fly ash, synthetic gypsum (also referred to as flue gas desulphurisation (FGD) gypsum), FGD solids and cenospheres. CCPs are generated when power plants burn coal to generate electricity, or through the use of emission control technologies. CCPs represent a significant proportion of the total waste combustion byproducts generated by our businesses.

AES recycles this waste product in engineered products including cement, concrete and road bases, which reduces overall emissions, waste and cost.

Ballylumford Water Efficiency Innovation

The water treatment plant (Reverse Osmosis, Electro-deionisation plant) at AES Ballylumford produces a variety of process waters (including demineralised water) through the desalination of seawater. A team of engineers sought to improve the production of process water required for electricity generation at the plant.

Their innovative solution led to a controlled reduction in water capacity and an increased efficiency for the first stage Reverse Osmosis step of the production process. The installed solution saves costs and carbon emissions by increasing the plant efficiency and reducing the electrical consumption associated with the production of process water; all without impacting on the generating capacity of the site.

This innovation was shortlisted as a finalist in the British Quality Foundation Awards and is being replicated at other AES plants around the world.