Inventory of aerosol and sulphur dioxide emissions from India: I—Fossil fuel combustion

Abstract

A comprehensive, spatially resolved (0.25°×0.25°) fossil fuel consumption database and emissions inventory was constructed, for India, for the first time. Emissions of sulphur dioxide and aerosol chemical constituents were estimated for 1996–1997 and extrapolated to the Indian Ocean Experiment (INDOEX) study period (1998–1999). District level consumption of coal/lignite, petroleum and natural gas in power plants, industrial, transportation and domestic sectors was 9411 PJ, with major contributions from coal (54%) followed by diesel (18%). Emission factors for various pollutants were derived using India specific fuel characteristics and information on combustion/air pollution control technologies for the power and industrial sectors. Domestic and transportation emission factors, appropriate for Indian source characteristics, were compiled from literature. SO₂ emissions from fossil fuel combustion for 1996–1997 were 4.0 Tg SO₂ yr⁻¹, with 756 large point sources (e.g. utilities, iron and steel, fertilisers, cement, refineries and petrochemicals and non-ferrous metals), accounting for 62%. PM_2.5 emitted was 0.5 and 2.0 Tg yr⁻¹ for the 100% and the 50% control scenario, respectively, applied to coal burning in the power and industrial sectors. Coal combustion was the major source of PM_2.5 (92%) primarily consisting of fly ash, accounting for 98% of the “inorganic fraction” emissions (difference between PM_2.5 and black carbon+organic matter) of 1.6 Tg yr⁻¹. Black carbon emissions were estimated at 0.1 Tg yr⁻¹, with 58% from diesel transport, and organic matter emissions at 0.3 Tg yr⁻¹, with 48% from brick-kilns. Fossil fuel consumption and emissions peaked at the large point industrial sources and 22 cities, with elevated area fluxes in northern and western India. The spatial resolution of this inventory makes it suitable for regional-scale aerosol-climate studies. These results are compared to previous studies and differences discussed. Measurements of emission factors for Indian sources are needed to further refine these estimates.

Introduction

It is now recognised that aerosols and sulphur dioxide (precursor gas to sulphate aerosol) play an important role in regional and global climate change, with some aerosol constituents (e.g. sulphate, organic matter (OM) and mineral matter) resulting in cooling and others (e.g. black carbon (BC)) in warming of Earth's atmosphere (Charlson et al (1991), Charlson et al (1992); Liousse et al., 1996; Tegen et al., 1997). In contrast to greenhouse gases, aerosols have short atmospheric lifetimes (about few days to a week), and would concentrate in source regions, having climatic effects with strong spatial and temporal variations. Aerosol emissions must be accurately estimated, with good spatial resolution, as a first step to understand their transport and climatic effects, on a regional scale.

India is one of the fastest growing economies in Asia, with an annual average GDP growth of 6.1% (WDR, 2000). This has resulted in an increase in commercial energy consumption in the last decade (38% between 1990 and 1998) (CMIE, 1999; TEDDY, 1999). As there are no current estimates of fossil fuel consumption and pollutant emissions compiled by Indian regulatory agencies, these are needed for recent base years, with detailed spatial resolution. This work is also relevant in context of the recently completed Indian Ocean Experiment (INDOEX) (1998–1999), to study the aerosol transport, chemistry, and their climatic effects over Indian subcontinent and Indian Ocean (Ramanathan et al., 1997). The objective of this work was to develop a comprehensive spatially resolved aerosols and SO₂ emissions inventory for India for the latest base year, to serve as an input to the aerosol-climate modelling studies related to INDOEX.

Previous global emissions inventories have included SO₂ and aerosol emissions from fossil fuel combustion in India (Cooke et al., 1999; Cooke and Wilson, 1996; Liousse et al., 1996; Penner et al., 1993; Spiro et al., 1992). In these inventories, national average estimates of per capita fuel consumption were used, which were reported, for example, by the International Energy Agency (IEA), for base years 1984–1990, and distributed based on population density. To improve the spatial distribution of the fuel use and emission estimates, some sectorisation was introduced to differentiate the power sector from other industries (Arndt et al., 1997; Akimoto and Narita, 1994). Further sectorisation was recently introduced (Garg et al., 2001) using fuel consumption data from Government of India databases for the base years 1990 and 1995.

In the previous estimates, emission factors of pollutants (SO₂, BC, OM) have been used at an aggregate level. Average fuel-based emission factors have been used, in general, without information about the production and pollution control technologies used in various industrial sectors. These would introduce uncertainties in the emissions, e.g. the SO₂ emitted or retained in a process, or the relative amounts of organic and elemental carbon formed at different combustion temperatures. Also, in the absence of technology related information, assumptions have been made to enhance pollutant emission factors by an arbitrary value (e.g. Cooke et al., 1999) above that applicable to the industrial process in a developed country. In many cases, global average fuel characteristics were used while, for example, Indian coals would have significantly higher ash and lower sulphur content than the global average (Coal Atlas of India, 1993).

In this study, an attempt has been made to develop a comprehensive emission inventory, which links plant-by-plant process and control technology, and appropriate fuel composition, to the best available emission factors to estimate emissions from different sectors. An analysis of the transportation and domestic sectors was made to identify and develop appropriate/realistic emission factors and estimate emissions for India. The objectives of the present paper are: (i) construction of fossil fuel consumption database for India for the base year 1996–1997 (the latest data available at the time this study was started), (ii) development of realistic emission factors, for SO₂ and aerosols, from industrial, transportation and domestic sources in India, (iii) construction of a spatially resolved (0.25°×0.25°) emission inventory for SO₂ and aerosols (PM_2.5 or particulate matter (PM) <2.5 μm diameter, BC, OM and the “inorganic fraction”) and projection of the emissions to 1998–1999 (INDOEX period).