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Environmental implications

CO2 emissions in Sri Lanka, both in absolute as well as in per capita terms, are low in comparison to other countries of South Asia. For example, CO2 emissions per capita (in 1999) were only 56 per cent of India’s and 13 per cent of the world average. Emission levels calculated per unit of GDP are also low, mainly due to the dominance of hydropower generation and low energy intensity of the production sectors.

Until quite recently, significant thermal generation occurred only in the drought years. However, this situation will change in the years to come. Suggested expansion sequences suggests a 67 per cent increase in the thermal share (from the present 40 per cent) by 2016, as almost all new plants in the foreseeable future will be fossil fuel based. Hence a substantial increase in the use of fossil fuels in the power sector seems inevitable.

In 1994 Sri Lanka approved ambient air quality standards, a proposed set of emission standards. At present all thermal power projects have to comply with these ambient air quality standards, which for particulate matter, NOx and SOx emissions are relatively stringent. Proposed Sri Lankan standards lie in between proposed World Bank standards and the standards of other Asian countries, such as the Philippines, India and Indonesia.

Emission control technologies

According to the base case generation expansion planning sequence mentioned under “Generation Planning Studies”, 1,500 MW coal-fired plants, 628 MW combined cycle plants, 62 MW of diesel, and 280 MW of gas turbines, will be added to the Sri Lankan system in the next 15 years starting from 2002. The impact on the environment due to particulate and air-emissions from these additions, and the effectiveness of using control devices to mitigate those impacts, are analysed here. Three types of gaseous emissions are considered in the analysis: SOx, NOx, and CO2.

When applying control technologies, one must have an idea about availability and capability of different control technologies. Studies have shown that the use of state-of-the-art engineering practices could often meet stipulated air quality standards without specific control devices. However, there are instances where emission control is mandatory. For example for coal plants, the use of high-quality, low-sulphur coal (0.5 per cent) reduces SOx emissions to levels below the standard, but, definitely there has to be some form of control of particulate emissions. Low-NOx burners are an integrated part of most commercially available combined cycle plants, which are capable of reducing NOx emissions to very low levels.

Hence, the present study considers the following control technologies: Electrostatic precipitators (ESP’s) for control of particulate emissions in coal-based plants, and low-NOx burners for control of NOx in coal-fired plants and combined cycle plants. No specific control devices were employed for control of SOx emissions.

Emission factors

One problem in analysing environmental implications of electricity generation is correctly assessing “emission coefficients” or, more commonly, “emission factors”. Choice of different sources can lead to overestimation of real emissions. Generally, particulate emissions depend both on the plant technology and the type of fuel burned. In the present study, emission factors were either calculated based on stoichiometry or chosen from a single source. CO2 and SO2 emission factors were calculated based on fuel characteristics, while NOx emissions, which depend on the plant technology, were obtained from a single source.

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Energy Security Section, Environment and Development Division,
United Nations Economic and Social Commission for Asia and the Pacific