Life cycle impact assessment (LCIA) is an important phase of the LCA methodology as it facilitates categorization of the environmental impacts linked with the products or process (Praene and Rakotoson, 2017). While the method of life cycle assessment of coal-based electricity generation is more a less universal it is a demanding challenge to recognise the variation between technology in different countries and it was coupled with the variation in the quality of coal.
In accordance with the guidance provided by ISO14044 (ISO 2006) standards, allocation has not been considered here. As this is a cradle to gate study, the system boundary includes the phases only until the generation of electricity (Martínez et al., 2009). The final phase of the LCA process is Life cycle interpretation.
The two main objectives of life cycle interpretation as defined by the International Organization for Standardization (ISO) are:
- To analyze outcomes, reaching conclusions, describing limitations and making recommendations based on the results of the preceding phases of the LCA and transparently disclosing the outcomes of the interpretation of the life cycle;
- To provide and easily understandable, complete, and consistent presentation of the findings of an LCA study, according to the goal and scope of the study.
Electricity generation from coal-fired thermal power plants in India produces the largest amount of CO2 per unit of energy released by combustion. The findings of this analysis include the environmental impacts of the selected coal-fired thermal power plants using the ReCiPe method from the cradle to gate perspective.
5.1 Global Warming and climate change potential:
The Global Warming Potential (GWP) is measured in kg CO2 equivalents per kWh of electricity generation. The total GWP for the three power plants (PP1, PP2 & PP3) is 1,100 g CO2eq/kWh, 1,287 g CO2eq/kWh and 898 g CO2eq/kWh respectively as shown in figure 6. PP1, PP2 uses Indian coal for electricity generation which is procured locally, while PP3 uses imported Indonesian coal. It is clearly evident from the findings that imported coal has lowered GHG emissions compared to thermal power plants running primarily on Indian coal.
Murray and Lopez (1996) originally investigated the DALY-concept for the World Health Organisation which Hofstetter (1998) later introduced into LCA. Evaluation of the adverse effects (damage) on human health using the concept of ‘Disability-Adjusted Life Years’ (DALY) when implementing a Life cycle assessment approach (Norris, 2006; Kobayashi et al., 2015; Arvidsson et al., 2016). As illustrated in Figure 7. the disability-adjusted life years (DALY) at three geographical locations in India for coal based electricity generation is presented. The estimation from PP1 shows 4.00E-07 DALY per kWh, PP2 shows 4.20E-07 DALY per kWh and PP3 that uses imported coal shows that total human health impact is 2.90E-07 DALY per kWh of electricity generation (from upstream and combustion processes) due to climate change.
5.2 Comparison with existing Literature
The life cycle assessment results from this study were used to perform a comparative assessment of emissions reported from other countries as presented in figure 8. Only one LCA study for coal-fired electricity generation conducted in India was found and therefore power plant which is used for comparison with our results. The results obtained in this study have been compared with international studies from Japan, Thailand, U.S., Turkey, Europe, U.K., Pakistan Netherlands, and Mauritius.
CO2 emissions from PP2 (India) are the highest and the emission observed from Turkey is at the minimum.
The higher global warming potential of the Thermal Power Plant in India is evident from the use of coal with high ash content with old technology which does not provide optimum efficiency.
This study listed various impact categories such as ecotoxicity, climate change, ozone depletion, acidification potential, photochemical oxidation based on inventory data for life cycle assessment.
The data assessment produced characterization results related to the relevant data on eutrophication potential and acidification potential as shown in Figures 9 and 10 Emissions towards GWP are expressed in kilogram of CO2 equivalents as shown in fig. 11
Figure 11 presents the GWP in kg CO2 equivalents per kWh of electricity generation. The total GWP (upstream and combustion processes) due to coal thermal power plants is 876 g CO2 eq/kWh and 987 g CO2 eq/kWh, respectively, whereas around 526g CO2 eq/kWh from combustion imported coal PP3, respectively. The results show that Indian coal has higher global warming impacts from GHG emissions when compared to imported coal.
NOx causes damage to vegetation and aquatic life through acid rain. It is also a precursor for photochemical smog contributors (Ozone, PAN, HNO3) in troposphere which causes damage to the human respiratory system as it affects Ozone (O3) balance. NOx can contribute to eutrophication and influences ecosystem by nutrient overload. The Photochemical Ozone Creation Potential of coal electricity generation are presented in Figure.12
5.3 Summary and suggestion for each power plant
5.3.1 Power plant – Chhattisgarh (PP1):
PP1 is a conventional power plant running on low load factors at an efficiency of just 30%
(net efficiency, higher heating performance - HHV). It operates on the old pulverized coal technology which is the most commonly used alternative for coal-firing in India as well as globally.
PP1 primarily uses Indian coal for power generation, which has high ash content that contributes to the creation of huge quantities of fly ash. The plant management and authorities are working to divert this waste to other sectors where it can be used as raw material, such as cement and bricks manufacturing industry. Gigantic heaps remain stacked up, even after extensive efforts to regulate the tremendous quantity of fly ash generated.
This power plant was built before 1980. Because of the age of the power plant, reconstruction and upgrade is a cost-effective choice to increase its performance.
Retrofitting would boost the setting of the plant and add to the existing capacity of power generation at an additional cost.
5.3.2 Power plant – Bihar (PP2):
All the units of PP2 have adopted subcritical technology which can produce power at an efficiency of about 33%. The power produced here covers the demands of the northern, western, eastern, and north-eastern regions of India. Though Sub-critical technology has been in service for a while now; through renovation, modernization measures, there is a scope to improve the efficiency and performance of these plants. As a large quantity of fly ash is generated here, the authorities initiated the process of making fly ash bricks at the power plant site itself. This intervention led to the implementation of a local government policy that is mandatory to use of ash bricks prepared, within a 100-kilometer radius from the power plant site. Only fly ash bricks which minimise the use of traditionally prepared bricks should be used for large national highway building schemes and other developmental projects.
5.3.3 Power plant – Mumbai (PP3):
PP3 is located Eastern suburbs of Mumbai and has an installed capacity of 1580 MW. This unit of capacity 500MW was installed in the mid-1980s which can run on gas or oil. Due to the decline in the supply of gas this unit is only placed into service when demand rises urgently or unexpectedly. While this is currently, a standby unit the company expects to be able to use it in the normal stable generation of electricity.
It is a subcritical thermal power plant supporting the regional grid. The coal is sourced for this plant is sourced entirely from Indonesia. A regulated system for the management of sulphur oxide the flue gas desulfurization (FGD) unit and an electrostatic precipitator is installed for control of particulate matter. PP3 has a well-defined environment policy and management system in place. The parent company has established a Corporate Safety, Health & Environment Department (C-SHE) that is responsible for all environmental and safety activities in the company.
In the supercritical unit improved efficiency is observed as it utilises higher temperature and pressure, lower fuel consumption per unit of energy, and decreased greenhouse gas (GHG) emission. The reduction in CO2 emissions units would be between 8- 10 percent. Lower fuel consumption has a direct effect on reducing other emissions as well. Supercritical units operate above critical point parameters at 225.56 kg/cm2 and 374.150C, where the density of water is the same as that of steam. Also, the latent heat is zero at this point, restricting the development of steam-water mixed-phase resulting in reduced fuel heat input. It is implied that subsequent attempts should be made to prepare for more advanced and effective ultra-supercritical technology.