GHG footprint of Major cities in India

Greenhouse gases are those gaseous constituents of the atmosphere, both natural and anthropogenic, that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared radiation emitted by the Earth’s surface, the atmosphere itself, and by clouds [1, 2]. Concentration of greenhouse gases (GHG’s) in the atmosphere has increased rapidly due to burgeoning anthropogenic activities coupled with population growth resulting in significant increase in the temperature of the earth. The energy radiated from the sun is absorbed by these gases making the lower part of the atmosphere warmer leading to phenomenon known as natural greenhouse gas effect. These effects were amplified with emission of gases from various anthropogenic activities consequent to industrialization and urbanisation. Initially in 1950’s based on infrared absorption model, CO2 was identified as agents of changes in the atmosphere. Subsequently several studies confirmed that species of carbon (CO2 and CH4), Nitrogen (N2O) and CFCs are crucial role in global warming and changes in the climate [3, 4]. Increase in the concentration of these greenhouse gases results in global warming. Atmospheric concentrations of GHG gases have increased due to increasing emissions of GHGs during post industrialization era due to human activities. Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydro fluorocarbons (HFCs), per fluorocarbons (PFCs) and sulfur hexafluoride (SF6) are the major greenhouse gases. Among the GHG’s, carbon dioxide is the most dominant gas causing global warming which accounts for nearly 77% of global total CO2 equivalent GHG emissions [2].

In 1958, attempts were made towards the high-accuracy measurements of atmospheric CO2 concentration and documented the changing composition of the atmosphere with the time series data [5, 6]. The increasing abundances of two other major greenhouse gases, methane (CH4) and nitrous oxide (N2O) in the atmosphere have been reported [7]. Methane levels were found to rise at a rate of about 1% per year [8, 9, 10] but then during 1990s its rate retarded to an average increase of 0.4% per year [11]. The increase in the concentration of other greenhouse gas N2O is smaller, found to be about 0.25% per year [12, 13]. Second class of greenhouse gases - the synthetic HFCs, PFCs, SF6, CFCs, and halons did not exist in the atmosphere before the 20th century [14]. CF4, a PFC, is detected in ice cores and appears to have an extremely small natural source [15].

The establishment of Inter-Governmental Panel on Climate Change (IPCC) in the year 1988 by United Nations organizations [16], and the formation of United Nations Framework Convention on Climate Change (UNFCCC) gave impetus towards quantifications of greenhouse gas (GHG) concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with climate system. Adaptation of Kyoto Protocol in the year 1997 necessitated developed economies to reduce their collective emissions of six important greenhouse gases by at least 5.2% as compared to 1990 level during the period 2008-2012 [16]. These endeavors necessitated GHG accounting at the regional levels. Carbon dioxide, nitrous oxide and methane are the major greenhouse gases (GHG).

Carbon Dioxide (CO2) Emissions: CO2 abundance was found to be significantly lower during the last ice age than over the last 10000 years of the Holocene as per the initial measurements [17, 18, 19]. CO2 abundances ranged between 280 ± 20 ppm from past 10000 years present up to the year 1750 [20]. There was an exponential increase of CO2 abundance during the industrial era to 367 ppm in 1999 [21, 22, 23, 24, 25, 26, 27, 28] and to 379 ppm (in 2005).
Methane (CH4) Emissions: Anthropogenic activities like fossil fuel production, enteric fermentation in livestock, manure management, cultivation of rice, biomass burning, and waste management releases methane to the atmosphere to a significant extent. Estimates indicate that human related activities release more than 50% of global methane emissions (EPA, 2010). Natural sources of methane include wetlands, permafrost, oceans, freshwater bodies, non-wetland soils, and other sources such as wildfires. Accelerating rise in methane and nitrous oxide concentrations were reported during the 20th century and constant abundance of 700 ppb until the 19th century. A steady increase brought methane abundances to 1745 ppb in 1998 [28, 29] and 1774 ppb in 2005 [30].
Nitrous Oxide (N2O) Emissions: Nitrous oxide (N2O) is produced by both natural sources and human-related activities. Agricultural soil management, animal manure management, sewage treatment, mobile and stationary combustion of fossil fuel and nitric acid production are the major anthropogenic sources. Nitrous oxide is also produced naturally from a wide variety of biological sources in soil and water, particularly from microbial action [31] from the measurements for N2O it is found that the relative increase during the industrial period is smaller (15%). The analysis showed a concentration of 314 ppb in 1998 [28], rising to 319 ppb in 2005.

Having understood the effects of various gases in the atmosphere it is also essential to understand that the climate regime is a complex, inter-related system consisting of the atmosphere, land surface, snow and ice, oceans and other bodies of water and living things which is proving as a serious threat to global community and temperature [32, 33, 34, 35]. Rising global temperatures will affect the local climatic conditions and also melt the fresh water ice glaciers causing the sea levels to rise Universal scientific understanding of this phenomena of earth’s climate change is that it mainly caused by greenhouse gas emissions generated by human activity [4, 36, 37] . Extensive studies have been carried out to study the pattern of global and regional mean temperature with respect to time [38, 39, 40]. The atmospheric concentrations of carbon dioxide equivalent with the possibility of rise in global temperatures beyond certain levels were reported earlier [41]. The recent (globally averaged) warming by 0.5°C is partly attributable to such anthropogenic emissions [41]. Change in climate also results in extreme weather events like very high temperatures, droughts and storms, thermal stress, flooding and infectious diseases. In the last 100 years the mean annual surface air temperature has increased by 0.4-0.6°C in India [42, 43]. This necessitates understanding the sources of global greenhouse gas emissions to implement appropriate mitigation measures.

1.1 GHG footprint and economic growth: The transition to a very low carbon economy needs elementary changes in technology, regulatory frameworks, infrastructure, business practices, consumption patterns and lifestyles [44, 45]. Over the past decade, the emission of greenhouse gases into the atmosphere has caused a concern over global warming with efforts focusing on minimizing the emissions. Heavy industries are transferred to knowledge-based and service industries which are relatively cleaner as the economic development continues [46] and at advanced levels of growth, there was a gradual decrease of environmental degradation because of increased environmental awareness and enforcement of environmental regulation [41]. There is a need for a target to be set which aids the local and national governments to frame climate change policies and regulations. Carbon dioxide emissions and energy consumption are closely correlated with the size of a country’s economy [45, 47, 48, 49]. Carbon intensity is one of the most important indicators which help in measuring a country's CO2 emission with respect to its economic growth. Carbon intensity refers to the ratio of carbon dioxide emissions per unit of economic activity, usually measured as GDP. It presents clear understanding of the impact of the factors that are responsible for emissions and also helps the policy makers in formulating future energy strategies and emission reduction policies [50]. The analysis of changes in carbon intensity in developing countries helps in optimizing fuel-mix and economic structure; meanwhile it also provides detailed information on the mitigation in the growth of energy consumption and related CO2 emissions.

Carbon intensity value drops if there is a decrease in emissions or sharp rise in the economic growth of the country. Carbon dioxide emissions resulting from the consumption of energy from the major countries were compiled from published literatures (International Energy Statistics, United States Energy Information Administration, EIA). Economic growth represented in terms of constant US $ 2000 is obtained from the World Bank [51]. GDP in domestic currencies were converted using 2000 official exchange rates. Figure 1 illustrates the carbon intensity trend across major carbon players in the globe. India’s overall carbon intensity of energy use has marginally decreased in recent years despite coal’s dominance. Strong penetrations of wind capacity and efficiency improvements in coal-based electricity production are some factors that are responsible for the decline of carbon intensity [52, 53].

1.2 GHG footprint: Organizations and governments across the globe are looking for strategies to reduce emissions from greenhouse gases from anthropogenic origin, responsible for global warming [49, 50].The increasing interest in GHG footprint assessment comes as a result of growing public awareness of global warming. The global community now recognizes the need to reduce greenhouse gas emissions to mitigate climate change [54, 55, 56, 57]. Many global metropolitan cities and organizations are estimating their greenhouse gas emissions and developing strategies to reduce their emissions.

“GHG footprint” is the total amount of greenhouse gases (GHG’s) impacting the environment produced both directly and indirectly due to various human activities, expressed in equivalent tons of carbon dioxide. The total greenhouse gas emissions from various anthropogenic activities (sectors) from a particular region are expressed in terms of carbon dioxide equivalent, which indicate the GHG footprint of that region [60]. Carbon dioxide equivalent (CO2e) is a unit for comparing the radiative forcing of a GHG (measure of influence of a climatic factor in changing the balance of energy radiation in the atmosphere) to that of carbon dioxide [61, 62]. It is the amount of carbon dioxide by weight that is emitted into the atmosphere that would produce the same estimated radiative forcing as a given weight of another radiatively active gas [56].

Carbon dioxide equivalents are calculated by multiplying the weight of the gas being measured by its respective Global Warming Potential (GWP) [63, 64, 65]. It is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. As defined by the Intergovernmental Panel on Climate Change (IPCC), a GWP is an indicator that reflects the relative effect of a greenhouse gas in terms of climate change considering a fixed time period, such as 100 years (GWP100 expressed as a factor of carbon dioxide (whose GWP is standardized to 1). GWP depends on factors such as absorption of infrared radiation by a given species, spectral location of its absorbing wavelengths and the atmospheric lifetime of the species [66]. The Global warming potentials of major greenhouse gases over the next 20 years [67] are 1 for CO2, 25 for CH4, 298 for nitrous oxide [1, 2].

1.3 Need for Estimation of GHG Footprint: GHG footprints have the potential to reduce the impact on climate change by increasing consumer awareness and fostering discussions about the environmental impacts of products. It offers valuable information for the sustainable urban planning for policy makers and the local municipalities [68, 69, 70, 71, 72, 73, 74]. This entails quantification of sector-wise GHG’s and computation of GHG footprint (aggregation of carbon equivalents of GHG’s).

1.4 GHG emissions inventory in India: In India, research has been carried out on different features of climate change, but lacks dedicated reports on assessment of climate change. Asian Development Bank’s report on “Climate change in Asia: India Country Report” was the first attempt to consolidate the information on climate change in India [75]. The study was limited to the collection of literature and certain studies on impacts of Climate Change on Agriculture, Water and Forests besides sea level rise [76]. Under Asia Least Cost Greenhouse Gas Abatement Strategy Project [77], a report was prepared on inventory of greenhouse gas emissions along with trace gases and sinks for the year 1990 and also the projections for 2020. In the year 2004, towards fulfillment of obligation under the UNFCCC, India submitted its Initial National Communication to the UNFCCC Secretariat which was a well synchronized report and serious efforts were made to assess the greenhouse gas emissions of anthropogenic origin and removal by sinks for at the 1994 level from fuel combustion and fugitive emissions from the energy sector, industrial processes and product use, agriculture sector, land use, land use change and forestry and waste management practices using revised Intergovernmental Panel on Climate Change Guidelines 1996 [78].

Currently, India is preparing its second national communication to the UNFCCC for the base year 2000. However, as there is a need for the latest data on greenhouse gas emissions from the country sector-wise.

Measurements of CO2 and other gases from coal based thermal power plants in India was done and the emission rates of the GHGs was found to be depended on factors like quality of coal mixture/oil, quantity used for per unit generation, age of the plant and amount of excess air fed into the furnace [79]. Study of large point source (LPS) emissions from India was carried out [89] for 1990 and 1995 using IPCC 1996 methodology, which showed CO2 and SO2 emissions being the major gases from the power plants.

Also, diverse studies have been carried out to calculate the greenhouse gas emissions resulting from the consumption of electricity for which a wide variety of fossil fuels are used for electricity generation [84,85,90,91,92].

Estimation of emissions from vehicles has been studied using various model calculations [112]. There are studies that are carried out which calculate the emissions on the basis of the activity data, vehicle kilometer travelled, vehicle category and sub category [5, 77, 113, 114, 115, 116]. Emission factors for Indian vehicles have been developed by the Automotive Research Association of India in co-ordination with MoEF, CPCB and State Pollution Control Boards [117]. Inventory estimates for the emissions of greenhouse gases and other pollutants and effects of vehicular emission on urban air quality and human health are studied in major urbanized cities in India [81, 118, 119, 120, 121].

GHG Emissions in Industrial Sector:Industry is a major source of global greenhouse gas emissions. Industrial sector is responsible for approximately one-third of global carbon dioxide emissions through energy use [122]. In India, emission estimates from large point sources such as thermal power, steel industry, cement plants, chemical production and other industries are carried out by various researchers [123, 124]. CO2 emissions from iron and steel, cement, fertilizer and other industries like lime production, Ferro alloy production and aluminum production have been estimated [95, 97].

Six industries in India have been identified as energy-intensive industries: Aluminum, cement, fertilizer, iron and steel, glass, and paper. The cement sector holds a considerable share within these energy-intensive industries [125, 126]. At the country level, trends of greenhouse gas emissions from industrial processes are studied which shows 24,510 CO2 equivalent emissions in the year 1990, 102,710 CO2 equivalent emissions in 1994 and 168,378 CO2 equivalent emissions in 2000 and 189,987.86 CO2 equivalent emissions in 2007 [127, 128, 129]. Under the aegis of INCCA, a national-level GHG inventory for CO2, CH4 and N2O inventory was published in 2010 for the base year 2007 which showed from industrial processes and product use [128].

GHG Emissions in Agriculture Sector: Agricultural activities contribute directly to emissions of greenhouse gases through a variety of processes. The major agricultural sources of GHGs are methane (CH4) emissions from irrigated rice production, nitrous oxide (N2O) emissions from the use of nitrogenous fertilizers, and the release of carbon dioxide (CO2) from energy sources used to pump groundwater for irrigation [130]. Where there is open burning associated with agricultural practices, a number of greenhouse gases are emitted from combustion. All burning of biomass produces substantial CO2 emissions. In India the crop waste generated in the fields is used as feed for cattle, domestic biofuel and remainder is burnt in the field [131]. Rice paddy soils contain organic substrates, nutrients and water, thereby resulting to be an increasing source of methane resulting from anaerobic decomposition of carbonaceous substances [132]. The anaerobic bacterial processes in the irrigated rice cultivated fields are considered to be among the largest sources of methane emission [133] and the annual global contribution of methane is estimated to be approx. 190 Tgy-1[134, 135].

During recent years, several studies on CH4 emission from Indian rice fields have been carried out by different researchers to study the effect of soil type, season, water regime, organic and inorganic amendments and cultivars [136-144]. Average methane flux varied significantly with different cultivars ranging between 0.65 and 1.12 mg m-2 h-1[120]. CH4 emissions from Indian rice paddies, therefore, is estimated to be 3.6±1.4 Tgy-1, which is lower than 4.2 (1.3 to 5.1) Tgy-1 obtained using the IPCC 1996 default emission factors [145]. India emitted 3.3 million tons of CH4 in 2007 from 43.62 million ha cultivated [146-148]. Application of fertilizer-N in upland irrigated rice has led to increased N2O emissions [96, 97, 146, 147]. Total seasonal N2O emission from different treatments ranged from 0.037 to 0.186 kg ha-1 [68, 83, 149, 150, 151].

GHG Emissions in Livestock Sector: There are two major sources of methane emission from livestock: Enteric fermentation resulting from digestive process of ruminants and from animal waste management [30, 31, 152]. Animal husbandry accounts for 18% of GHG emissions that cause global warming [153]. Methane emission from enteric fermentation from Indian livestock ranged from 7.26 to 10.4 MT/year [154]. In India more than 90% of the total methane emission from enteric fermentation is being contributed by the large ruminants (cattle and buffalo) and rest from small ruminants and others [155]. Production and emission of CH4 and N2O from manure depends on digestibility and composition of feed, species of animals and their physiology, manure management practices and meteorological conditions like sunlight, temperature, precipitation, wind, etc. [156, 157].

In India, various studies have been carried out in which the emission inventories for enteric fermentation and manure management are done at the national level [81, 89, 91, 145, 153]. Total emission of methane from Indian livestock was estimated as 10.08 MT considering different categories of ruminants and type of feed resources available in different zone of the country [158]. CH4 and N2O country specific emission factors for bovines were found to be lower than IPCC-1996 default values. Inventory estimates were found to about 698 ± 27 Gg CH4 from all manure management systems and 2.3 ± 0.46 tons of N2O from solid storage of manure for the year 2000 [145]. Using the emission factors provided in the report [146], it is estimated that the Indian livestock emitted 9.65 million tons in 2007. Buffalo is the single largest emitter of CH4, as it constitutes 60% of the total CH4 emission from this category, simply because of its large number compared to any other livestock species and also because of the large CH4 emission factor with respect to others [76]. By using the IPCC guidelines, the total CH4 emitted from enteric fermentation in livestock is found to be 10.09 million tons and emissions from manure management is estimated about 0.115 million tons of CH4 and 0.07 thousand tons of N2O are emitted [76].

GHG Emissions Inventory in Waste Sector: The main greenhouse gases emitted from waste management is CH4. It is produced and released into the atmosphere as a by-product of the anaerobic decomposition of solid waste, where-by methanogenic bacteria break down organic matter in the waste. Similarly, wastewater becomes a source of CH4 when treated or disposed anaerobically. It can also be a source of N2O emissions as well due to protein content in domestically generated waste water [76, 159, 160]. Industrial wastewater with significant carbon loading that is treated under intended or unintended anaerobic conditions will produce CH4 [30].

Waste landfills are considered to be largest source of anthropogenic emissions and the methane emissions from the landfill is estimated to account for 3-19% of the anthropogenic sources in the world [24]. Landfill gas, a mix of primarily CO2 and CH4, is emitted as a result of the restricted availability of oxygen during the decomposition of organic fraction of waste in landfills [161]. Attempts have been done to account methane emissions for select landfill sites in India [81, 162-165, 166]
CH4 emission estimates were found to be about 0.12 Gg in Chennai from municipal solid waste management for the year 2000 which is lower than the value computed using IPCC, 1996 [30]. Attempts are made to estimate the realistic values of methane emission from municipal solid waste landfills in India using default IPCC 1996 guidelines and triangular method (FOD method) shows that the triangular method is more realistic and can be used in estimation in global basis [167]. The existing situation of municipal solid waste management in major cities in India are assessed and parameters like waste quantity generated, waste generation rate, physical composition and characterization of MSW in each of the cities are carried out [168]. Solid waste generated in Indian cities increased from 6 Tg in 1947 to 48 Tg in 1997 [169] with per capita increase of 1-1.33% per year [170]. As per INCCA (2010) [83], 604.51 Gg of CH4 was emitted from solid waste disposal sites in India.

Methane is generated from two categories of waste water - domestic and industrial. The main factor in determining the extent of CH4 production is the amount of degradable organic fraction in the wastewater [171] that is commonly expressed in terms of biochemical or chemical oxygen demand (BOD) or (COD). Methane emissions from disposal and treatment of industrial and municipal solid waste (MSW) are not a prominent source in India, except in large urban centers. In India, methane emissions from domestic/commercial and industrial waste water are found to be 861 Gg and 1050 Gg respectively for the year 2007 and about 15.81 Gg of nitrous oxide is emitted from domestic/commercial waste water sector [95, 96, 128].