Nitrogen Oxide (NO_x) Emissions

Our NO_x emissions are mainly a function of the ratio of coal to gas-fired generation and different operating factors (for example, the temperature at which fuel is burned, how much time is required to burn the fuel and the amount of oxygen in the combustion flame). Because natural gas is burned in a pressurized chamber, with minimal air and lower temperatures than what is needed for coal, less NO_x emissions are formed. The result: the more gas-fuelled electricity we generate, the less NO_x emissions we produce per unit of electricity.

NO_x emissions down slightly

In 2004, we reported a slight decrease in NO_x emissions, from 68,000 tonnes in 2003 to 66,400 tonnes. Similarly, our NO_x emission intensity improved eight per cent to 1.42 kilograms per megawatt hour, from 1.50 kilograms the previous year. The main contributor to this improvement was our growing use of low emission, gas-fired electricity generation.

Genesee 3 plant advances emission controls

In March 2005, TransAlta and EPCOR began commercial operation of the Genesee 3 generation plant, west of Edmonton. The 450-MW facility is the most advanced coal power plant ever built in Canada.

A joint venture between the two companies, Genesee 3 is Canada’s first generation facility to use a supercritical pressure boiler. In a supercritical boiler higher temperatures and steam pressures, together with a high efficiency steam turbine, create a more efficient process for converting thermal energy into electricity. The process uses less coal per megawatt hour of electrical energy than conventional processes, thereby reducing emissions.

The plant will produce half the NO_x emissions of existing coal-fired generation, and will prevent 99.8 per cent of fine particulate matter from reaching the atmosphere. It will also cut SO₂ emissions to 70 per cent below existing emissions.

The plant’s supercritical combustion and clean air technologies will reduce total CO₂ emissions to 18 per cent below the average Alberta coal plant. GHG emissions will be further offset down to the level of a natural gas combined cycle plant — a 52 per cent reduction in emissions.

Monitoring impacts of coal plants

In 2004, TransAlta and EPCOR launched regional ambient air quality monitoring programs and regional bio-monitoring programs. These programs are designed to determine if there are any long-term impacts on the environment from coal plants in the Wabamun-Genesee area.

The air emission programs will gather information about power plant impacts related to acid and mercury deposition and typical air pollutants such as SO₂, NO_x, ozone and particulate matter. The monitoring is being carried out by the West Central Air Shed Society, an environmental non-profit organization which is led by a multi-stakeholder Board and ensures third-party validation of data. At year-end, four new state-of-the-art ambient air monitoring stations were up and running and collecting valuable air quality data in the region.