Life Cycle Assessment of Natural Gas Power Plant: Calculation of Impact Potentials

Abstract

Natural gas is a growing energy source worldwide, with its market share increasing steadily. It is one of the primary fuels used in electricity production. Its high thermodynamic quality and low environmental impact make it the fastest growing energy source in the global energy sector. Natural gas is a relatively clean and efficient fuel, making it a good choice for electricity production and heating. Using natural gas in gas power plants and industrial thermal applications will reduce harmful pollutants. Despite its significance, it is crucial to understand its potential impact on the electricity supply. The objective of this study is to conduct a life cycle assessment from cradle-to-gate of a natural gas power plant to understand the impact on the global warming (GWP) potential, freshwater eutrophication potential (FEP) and terrestrial acidification potential (TAP) categories when producing 1 kWh of electricity. Using the SimaPro (version 9.2) software package and Rest of the World data to model the cradle-to-gate scenario, the study found that the processing of natural gas is the most crucial stage in all three impact categories, making it the hotspot (37-95%) for GWP, FEP and TAP, with CO2 contributing the most at the GWP, PO4 at FEP and NOx at TAP.

1. Introduction

Generally, global electricity generation comes from fossil fuels, that is, coal, oil, and natural gas, with thermal power plants producing most of this electricity [1, 2]. The power generation sector has been identified as the highest contributor to global greenhouse gas (GHG) emissions [3]. This trend is likely to continue as the demand for electricity increases. Global electricity generation modes are changing substantially due to depleting fossil resources and a looming climate emergency, putting pressure on countries to adopt low-carbon energy policies. According to the Intergovernmental Panel on Climate Change (IPCC), global economy electrification and grid rapid carbon footprint are potential measures for reducing greenhouse gas emissions (GHG) and keeping global warming at 1.5°C or below 2°C [4]. In the global energy sector, energy activities include extraction, conversion, intermediate and final energy use, accounting for approximately 75% of GHG emissions [5, 6], primarily due to burning coal, natural gas, and oil. Most of these burnings are used to generate electricity today. Replacing coal and oil with natural gas in power generation and industrial thermal applications will help reduce harmful pollutants. This emissions reduction qualifies natural gas as a cleaner fuel. With concerns about air quality and climate change, natural gas has a future role in global energy supply as a cleaner fossil fuel that is still abundant in supply, aided by the fact that renewable energy options remain limited in ability to scale up while cost-effective zero-carbon options can be harder to find in some [7, 8].

Power plants powered by natural gas are cheap and easy to build. In addition, they have exceptionally high thermodynamic efficiency compared to other conventional power plants. Natural gas power plants are less polluting than coal and oil plants because they emit less nitrogen oxides (NO_x), sulfur oxide (SO_x) and particulate matter (PM) [9]. Natural gas is used as their fuel in natural gas power plants to produce electricity. Natural gas is composed of hydrocarbons that exist naturally and is frequently discovered in petroleum and coal deposits, as well as in the form of hydrates on the ocean floor. The gas is formed by the decomposition of organic matter [10]. The gas can be liquefied by cooling it to a temperature of −162°C at atmospheric pressure [11]. The main constituent of natural gas is methane (CH₄) mixed with smaller amounts of, moisture or water vapor, nitrogen propane, ethane, carbon oxide (CO₂), helium, and hydrogen sulfide [12]. The thermodynamic properties of natural gas from its combustion produce negligible amounts of sulfur, mercury, particulates and small quantities of NOx, making natural gas a cleaner fuel than gasoline and diesel [7]. A natural gas engine refers to a mechanical engine that utilizes natural gas as its primary fuel source for the generation of power, whether in the form of mechanical energy or electrical energy.

Natural gas has several advantages over other fossil fuels, including affordability, accessibility, environmental friendliness, compatibility with conventional spark and compression ignition engines, and low operating costs [13]. These advantages make natural gas appealing for power generation and other engine applications. Similarly, natural gas power plants offer various advantages, such as effective combustion, cost-effectiveness, adherence to environmental standards, enough availability and supply, and the generation of cleaner energy [13]. Despite these advantages, examining the environmental impact is crucial before deciding whether to invest in such a resource. Some of those studies include energy transition and air pollution impact [14], biodiesel production impact [15] and impact of electricity options, which includes renewables [16, 17, 18, 19]. All electricity production has an environmental impact throughout its entire life cycle, from the production stage to end-use.

Life cycle assessment (LCA) methodology has been widely used to evaluate the environmental impacts of energy systems and has gained popularity in areas where environmental impact is of concern [20, 21, 22]. The primary objective of this study is to assess the environmental ramifications associated with the operation of a gas power plant through the utilization of a Life Cycle Assessment (LCA) methodology. There have been several LCIA studies conducted in the past, including ReCiPe, CML, TRACI, IMPACT2002+ and IPCC. Several impact categories ranging from one up to 10 environmental categories have been investigated [23, 24]. Also, the impact categories seem to differ across studies. Impact categories such as global warming potentials (GWP), ozone depletion potentials (ODPs), human toxicity potentials (HTP), acidification potentials (AP) and eutrophication potentials (EPs) are more often used at the midpoint characterization in LCA studies for electricity generation [25]. Ecoinvent, a database that provides information on potential environmental impacts, was the most widely used database across the research. Several LCA studies have been conducted to assess the different electricity generation in specific countries such as Poland [26], Portugal [17, 27], United Kingdom (UK), Belgium [28, 29], Denmark [30, 31], Pakistan [32], China [14] and Brazil [33, 34].

Wu et al. [14] used LCA in the integration model to quantitatively evaluate its environmental impact under three policy scenarios from 2016 to 2050. Under the deep-level cut of CO₂ emission to achieve emission reduction and carbon neutrality in China from energy transition and air pollution. CO₂, PM_2.5, PM₁₀, CO, NO_X and SO₂ were deemed to reduce by more than 71.4% compared to the 2016 records. There would also be an 81.8% - 88.5% decrease in the global warming potential, human toxicity potential, petrochemical ozone creation potential, particulate formation potential and acidification potential. Alizadeh and Avami [15] compared biodiesel production from palm oil and multi-feedstock using LCA in Indonesia to understand the environmental impact of biodiesel production. There was a higher environmental impact from using multi-feedstock at the plantation stage, with 9.89tCO₂ GHG emission per tonne in the land use of scrubbed plantation to just −3.42 tCO₂ of palm oil plantation on biodiesel production.

Roinioti and Koroneos [16], looked at the sustainability aspect of the electricity options (Lignite, Combined Cycle Gas Turbine – CCGT, Hydro, Small hydro, Wind, PV and Biogas-biomass) in Greece through LCA considering the environmental, economic, and social dimensions. This study only showed interest in the environmental viewpoint. Looking at the seven sustainable indicators under environment, Biomass (54.26 g CO₂ equ./Kw) had the worst impact under the Global Warming Potential indicator among the renewables, while Lignite station (1067.15 g CO₂ equ./kWh) had the overall worst impact followed by CCGT station (509.96 gCO₂ equ./kWh). Lignite exhibited the worst impact for Acidification Potential (2989.89 mg SO₂ equ./kWh) and for Tropospheric Ozone Precursor Potential (2644.63 mg TOPP equ./kWh). Biomass-biogas exhibited the worst impact for both Eutrophication Potential (891.61 mg PO₄ equ./kWh) and Photochemical Oxidation Potential (0.49 mg ethene equ./kWh). On the Ozone Depletion Potential, CCGT exhibited the worst with a 99.98 μg CFC-11equ./kWh value.

Kabayo et al. [17], performed a life cycle sustainability assessment on Portugal’s electricity (coal, natural gas, large hydro and small hydro, wind, and photovoltaic) generation from the environmental and socioeconomic impacts. Interest remained in the environmental impact for the essence of this study. The highest impact of the sources of electricity is in brackets next to the sustainable indicators considered: metal depletion (wind), fossil fuel depletion (coal), global warming (coal), ozone depletion (natural gas), terrestrial acidification (coal), freshwater eutrophication (coal), aquatic acidification (coal), water scarcity footprint (large hydro), and toxicity (photovoltaic). The environmental impact of renewable energy generation systems was analyzed comparatively using life cycle assessment for Europe, North America, and Oceania [18]. The energy-generation technologies included wind, photovoltaic, biomass, and hydropower. The indicators for the impact were ozone layer depletion, freshwater aquatic ecotoxicity and marine aquatic ecotoxicity, abiotic depletion, global warming, photochemical oxidation, acidification and eutrophication. Of all the generation systems, biomass was impacted the most, followed by photovoltaic.

Mahmud et al. [19] conducted a comparative LCA of solar-photovoltaic and solar-thermal systems to determine their environmental impact using 16 indicators. The result indicated that the solar-thermal system is more impactful compared to the photovoltaic. The study recommended careful component selection and reducing the impact related to solar panels, batteries and heat storage for better environmental performance. This study aimed to identify the hotspots of environmental impacts associated with natural gas power plants. The authors have solely considered and concentrated on Global Warming, Eutrophication and Acidification impact categories due to climate change using SimaPro (version 9.2) software package to assess the environmental impact of producing 1KWh of electricity from natural gas on human health. This study will cover the potential impact of producing 1 kWh of electricity from natural gas in detail on views from global warming, acidification and eutrophication.

2. Materials and methods

2.1 Environmental impact through life cycle assessment (LCA)

LCA evaluates the environmental impact emanating from a production process for a product stipulated in ISO 14040 within the process categories and boundaries [35]. The implementation of the aforementioned concept exhibits variability across different studies, contingent upon the explicitly stated objectives of each respective investigation. The LCA’s operation occurs at the following stages (Figure 1), which are (1) the goal and scope definition, (2) life cycle inventory (LCI), (3) life cycle impact assessment (LCIA) and (4) results and interpretation [36] through the energy and the materials used been quantified and the release of the wastes to the environment [37]. LCA has been used to investigate the environmental impact of the natural gas power plant. The modeling of the impacts was done by using SimaPro (version 9.2) software package.

Figure 1.

ISO 14040 LCA framework [36].

2.2 Definition of goal and scope

The first part of a standardized LCA is goal and scope definition, which includes a description of essential choices, such as why the LCA is being done, a comprehensive elucidation of the product or process along with its life cycle, accompanied by a depiction of the system boundaries. It is possible to comprehend why LCA is undertaken by stating the study’s purpose. However, various factors influence the system boundary, including the study’s aim, assumptions and intended audience. ISO 14040 recommends that the circumstances used to define the system boundary be defined and justified in the study’s scope [36]. The goal of this study is to investigate, quantify and compare the effect on the environment of producing 1kWh of high-voltage electricity from natural gas in a power plant. This is a ‘cradle-to-gate’ approach [37, 38]. Figure 2 shows the boundaries for the system.

Figure 2.

System boundaries for electricity production using a natural gas conventional power process.

The boundaries include the extraction phase (conventional onshore source) to the electricity production in a power plant’s busbar. This study did not consider inventory data on distribution, use, disposal/end-of-life, or waste treatment. In addition, the midpoint LCIA technique is used in this study. The functional unit of this work is 1 kWh net electricity produced from natural gas. This study normalized all the inputs to the functional unit.

The study focuses on the three impact categories from the 18 impact categories presented in the midpoint analysis characterization result. These are the Global Warming potential (GWP), Freshwater Eutrophication Potential (FEP) and Terrestrial Acidification Potential (TAP). At the time of the study, primary data was inevitably unavailable; hence, secondary data from the Ecoinvent database 3.7.1 [39, 40] was employed. Assumptions and uncertainties have been adequately adjusted as specified by the dataset documentation and data has been interpolated accordingly.

2.3 Life cycle inventory (LCI)

The Life Cycle Inventory (LCI) is the data collection phase of the LCA since analysis entails compiling input and output inventory data that are consistent with the product under consideration and cover various environmental factors [41]. The comprehensive data encompasses all inputs and outputs of the system, encompassing materials, resources, energy, and emissions across the whole life cycle of the process or product [42]. The data for this study was derived from the Ecoinvent (V 3.7.1) database, which was integrated into the analysis software. This dataset represents the production of high-voltage electricity in a conventional steam boiler natural gas power plant without CHP (combined heat and power). A cradle-to-gate inventory involves all the processes/flows, raw materials and essential requirements needed to make electricity from the power plant available in the busbar and ready for distribution. LCA can be performed from either an attributional or a consequential perspective. An attributional LCI attempts to describe the environmentally relevant physical flows from and to a life cycle product system [43] and can be used to assess a product’s environmental impact over time. Alternatively, consequential LCA describes how potential past or future decisions might have affected environmentally relevant physical flows [43, 44, 45]. This study used the attributional method resulting in the environmental implication of 1 kWh of electricity produced from the natural gas power plant. The inventory input/output data for 1kWh of high voltage electricity from natural gas in a power plant are included in Table 1. The analysis computation was based on the ROW (Rest of the World) data.

Materials/Input	Amount
Natural gas, high pressure	0.256 m^3
Gas powerplant 100 MW electrical	5.54e-10 unit
Water, completely softened	0.0598 kg
Water, decarbonised	1.99 kg
Residue from the cooling tower	−9.97e-06 kg
Water, cooling, unspecified natural origin	0.0589 m^3
Mode of transportation via pipeline	2.41e+12 ton/km.
Output
Electricity	1 kWh
Emissions to air
Carbon dioxide, fossil	0.533 kg
Methane	9.68e-06 kg
Nitrogen oxides	0.000366 kg
Sulfur dioxide	5.7e-06 kg
Emissions to water
Water	0.06 m^3

Table 1.

List of input/output data of 1kWh of high voltage electricity from natural gas in a power plant [46].

2.4 Life cycle impact assessment (LCIA)

The life cycle impact assessment (LCIA) is a process that converts the life cycle inventory (LCI) data into quantifiable environmental, social, and economic implications [47]. By converting the emissions and resource extractions contribute to environmental damage. Ratings, it aids in the interpretation of the evaluation [48]. It is a multi-issue technique for assessing potential environmental impact based on environmental resources (inputs and outputs) listed in the life cycle inventory. This is an attempt to link a product and its possible environmental impact. Flows are classified according to their environmental impact in the midpoint LCIA approach employed in this study. This method simplifies multiple flows by condensing them into a few common environmental impacts. This study, however, concentrates on three impact categories: global warming, eutrophication, and acidification. ReCiPe 2016 was used as the LCIA tool in this study [49, 50]. In SimaPro, GWP 100 factors are recommended as default in the Global Guidance for Life Cycle Impact Assessment Indicators and Methods (GLAM) [51]; the same is applied to GWP20 and GTP100 factors for sensitivity analysis. Those defaults are applicable to this study. More on ReCiPe can be found in the study of Ige et al. [50].

The LCIA (Life Cycle effect Assessment) process is founded upon the utilization of effect categories and characterization variables: classification, normalization, characterization, and valuation. Through classification, there is a grouping of the environmental impact measured to a sizeable recognized environmental impact category based on the availability of the process information. The characterization step’s responsibility is to assess each environmental impact contribution [52]. This is done by multiplying each substance’s amount by its characterization factor and finding the sum. The following equations from Huijbregts et al. [52]. study express the characterization formula types. Eq. (1) pertains to the variables that are generic in nature, whereas Eq. (2) pertains to the elements that are non-generic. The former factor is typically derived from characterization models and can be found in the literature as a database.

$$S_j=\sum _i{Q}_{j,i}{m}_i$$E1

where

$S_j$ = impact category j indicator

$m_i$ = size of the intervention of type i

$Q_{j,i}$ = characterization factor that links intervention i to impact category j

Eq. (2) denotes the potential variables of certain non-generic characterization aspects within the context of human health and the impact on the natural environment.

$$Q_{j,s,t}=\sum _l\frac{\mathit{\text{Effect}}\left(i,l,t\right)}{\mathit{\text{Emission}}\left(i,s\right)}=\sum _l\left(\frac{\mathit{\text{Fate}}\left(i,l,t\right)}{\mathit{\text{Emission}}\left(i,s\right)}\right)·\left(\sum _l\frac{\mathit{\text{Exposure}}\left(i,l,t\right)}{\mathit{\text{Fate}}\left(i,l,t\right)}\right)·\left(\sum _l\frac{\mathit{\text{Effect}}\left(i,l,t\right)}{\mathit{\text{Exposure}}\left(i,l,t\right)}\right)$$E2

where

subscript i = substance,

s = location of the emission,

l = related exposure area of the receptor

t = period during which the potential contribution to the impact is considered.

The normalization step is for comparison of the various impact across the impact classifications and inaccessible areas for prioritizing alternate product or resolving trade-offs between products [52, 53]. It is at this stage that the insignificant impact categories on the entire environmental impact result to the reduction of factors evaluated. According to Huijbregts et al. [52], normalization serves two primary objectives within the field of Life Cycle Impact Assessment (LCIA): firstly, it aims to situate the results of LCIA indicators within a wider framework, allowing for a more comprehensive understanding of their implications. Secondly, it seeks to standardize the results by aligning them with common dimensions, facilitating meaningful comparisons and analyses. A reference value is employed to split the aggregate of the outcome for each indicator within a certain category.

$$N_k=\raisebox{1ex}{$S_k$}\!\left/ \!\raisebox{-1ex}{$R_k$}\right.$$E3

where

k = impact category

N = normalized indicator

S = category indicator from the characterization phase

R = reference value.

The selection of the reference system is typically based on the overall indicator outcome for a specific country or region during a given year. In the context of a Life Cycle Assessment (LCA) study, the outcomes of normalization can facilitate the process of input grouping or weighting of effect categories, as well as provide a means to assess the relative significance of various impact categories [50, 53]. The inputs and outputs in the 1kWh of high voltage electricity from natural gas in power in Table 1 are divided into four production stages: Extraction, processing, transportation, and energy conversion. The connection between each step and the impact categories under investigation is established through the utilization of the Life Cycle Assessment (LCA) methodology. SimaPro (version 9.2) software application was used for all calculations. Table 2 shows all processes studied in each production stage. The mode of transportation in this study is a pipeline (2.41e+12 ton/km).

Production unit	Processes considered
Extraction of raw materials (natural gas)	Natural gas, including the inputs and outputs
Processing of raw materials (natural gas)	Inputs and outputs required for the processing of natural gas
Transportation	The transportation of natural gas from the extraction location to the gate of the plant
Energy conversion	Every process involved to get electricity ready in the busbar of the power plant for distribution

Table 2.

The processes examined in each stage of production of natural gas burnt in a power plant.

3. Results

The result represents data modeled after the ROW, including Austria, Belgium, Germany, Spain, France, the United Kingdom, Italy, Japan, Luxembourg, Netherlands and the United States of America. The following section explains the contribution of each unit process to the environmental impact and the major contributing processes throughout the life cycle. The environmental impact of each production process was studied in terms of Global Warming Potential (GWP), Freshwater Eutrophication Potential (FEP) and Terrestrial Acidification Potential (TAP). Table 3 presents the total characterization results for the three selected impact categories. (The values provided in these tables are the functional unit of this current work, 1 kWh of electricity produced.

Impact category	Unit	Results
Global warming	kg CO2 eq	6,05E-01
Freshwater eutrophication	kg P eq	8,28E-06
Terrestrial acidification	kg SO2 eq	2,52E-04

Table 3.

Characterization results of the three focused environmental impacts.

The GWP, FEP and TAP values for the impact results per functional unit (Table 3) are 6,05E-01 kg CO₂ eq, 8,28E-06 kg P eq and 2,52E-04 kg SO₂ eq, respectively. In this view, the impacts are mainly attributable to plant operation, with natural gas consumption and direct emissions to the atmosphere being the primary contributors. These results are consistent with the relevant scientific literature on electricity production from natural gas in power plants [54]. Further analysis was performed to determine each production stage’s contribution to these Impact potentials in a natural gas power plant. These stages include Extraction, Processing, Transportation and Energy conversion.

Global warming potential: 79.5% of the emission is from the energy conversion stage; 14.3% is from the extraction stage, 3.4% is from the processing stage and 2.7% is from the transportation stage, as shown in Figure 3. From Table 3, the global warming impact category has the highest value; it qualifies as one with the highest impact and consequently presents the energy conversion process as the highest contributor to the environmental impact related to the production of electricity from natural gas power plants. Terrestrial Acidification: 79.3% is from the extraction stage; 11.9% is from the energy conversion stage; the rest is from the processing and transportation stages. Also, roughly 100% of the contribution to Freshwater Eutrophication is from emissions from the extraction stage for every production of 1 kW of electricity from the natural gas power plant.

Figure 3.

Contribution of production stages to impact categories.

The GWP is majorly experienced at the energy conversion stage, whereas the eutrophication and acidification potentials are primarily experienced during the extraction stage, as shown in Figure 3. In a gas power plant, the chemical energy stored in the natural gas is converted into thermal, mechanical, and electrical energy. Thus, the maximum contribution to global warming observed due to climatic changes was recorded at the energy conversion stage (79.6%), which is understood to be the most demanding phase. Further analysis of the substance contributing to the GWP, FEP and TAP are discussed below.

3.1 Global warming potential (GWP)

The contributions of three GHGs, CO₂, N₂O, and CH₄, were considered when calculating the GWP, as shown in Figure 4. The global warming potential value of the process is 6,05E-01 kg CO₂ eq. as shown in Table 3.

Figure 4.

Contribution results for global warming potential.

The most significant contributor to GWP is CO₂ (94%), followed by CH₄ (5%) and N₂O (1%) emissions as shown in Figure 4. CO₂ is emitted in the most considerable quantity of air emission due to the fuel burning caused by global warming. The percentage value of CH₄ is attributed to the fugitive emissions from natural gas production. Most CH₄ results are from natural gas losses during raw material extraction and transportation. The energy conversion stage is the largest source of GHG emissions due to gas burning, accounting for 79.5% of total GWP.

3.2 Freshwater eutrophication potential (FEP)

The value of the Freshwater Eutrophication impact is 8,28E-06 kg P eq./kWh, as shown in Table 3. Phosphate (PO₄³⁻) emitted 99.7% into the waterbody and Phosphorus (P water) is 0.3%, as shown in Figure 5. (PO₄³⁻) is the major substance that contributed to the FEP.

Figure 5.

Contribution results for freshwater eutrophication.

Phosphorus (P waster) can directly regulate algae growth in aquatic ecosystems as vital nutrition, which has been recognized as a limiting factor for eutrophication [55]. Although PO₄³⁻ is soluble reactive phosphorus, algae can preferentially absorb it. Phosphorus (P) pollution can trigger severe marine eutrophication, leading to harmful algal blooms and seawater deterioration. Too much phosphorus can cause increased growth of algae and large aquatic plants, which can result in decreased levels of dissolved oxygen– a process called eutrophication.

3.3 Terrestrial acidification potential (TAP)

The terrestrial acidification value of the 1 kWh electricity production from the natural gas conventional power plant is 2,52E-04 kg SO₂ eq./kWh, as shown in Table 3. NO_x emitted 72% of the emission, followed by SO₂ with 27%, while NH₃ contributed 1%, as shown in Figure 6. This situation involves the extraction of natural gas as a raw resource. Burning fossil fuels containing sulfur, such as natural gas, always produce SO₂.

Figure 6.

Contribution results for terrestrial acidification.

Sulfur dioxide (SO₂) has been found to be a significant contributor to respiratory ailments in human populations, while also playing a substantial role in the formation of acid rain. The planet Earth. The process of anthropogenic ozone generation begins with the release of nitrogen oxides (NO_x) and/or non-methane volatile organic compounds (NMVOCs) into the atmosphere. Through subsequent chemical reactions, the ozone layer is generated. The elevated levels of ozone production in the Earth’s atmosphere have significant implications for both human health and the overall ecology. The impact of this phenomenon is evident in the occurrence of health complications and, in some cases, the extinction of certain species.

3.4 Normalization result

Normalization is necessary for comparing the various environmental impact categories since their units differ. This step presented the relative contribution of each impact caused by global warming, freshwater eutrophication and terrestrial acidification. A normalization step is conducted based on the total emissions to produce 1 kWh of electricity from the natural gas conventional power plant. The normalization results naturally show a similar trend as the characterization impact results (Figure 7).

Figure 7.

Normalized results of each impact category.

The normalization result of the global warming impact shows the highest value (7,57E-05 kg CO₂ eq) followed by the Freshwater eutrophication impact value of 127509E-05 kg P eq./kWh and Terrestrial acidification impact with a value of 615531E-06 kg SO₂ eq./kWh. The most harmful impact category in the normalization result is global warming due to the burning natural gas in the power plant.

4. Conclusion

This study examined the environmental impact of electricity production from the natural gas power plant. In this study, we used a cradle-to-gate method as a system boundary. Cradle-to-gate includes raw material extraction (natural gas), raw material processing (natural gas), transportation and energy conversion stages. The results of this study helped identify the environmental sustainability of 1 kWh of electricity production from a natural gas conventional power plant. The results show that the GWP is calculated at 6,05E-01 kg CO₂ eq./kWh. According to this study, CO₂ accounts for 94%, CH₄ 5%, and N₂O 1% of all air emissions are the three main sources of GWP. Electricity production from the natural gas conventional power plant is estimated at 8,28E-06 kg P eq./kWh for FEP. The TAP of 2,52E-04 kg SO₂ eq./kWh. According to the analysis, the environmental impact assessment showed a good environmental performance compared with other literature [16, 56]. The result showed that the environmental impact hotspot was the raw material processing (natural gas) stage.

Regarding production stages, the energy conversion stage (79.57%) is the main hotspot of the GWP. The raw material extraction, processing and transportation are often insignificant. At the normalization step, global warming impact with the values of 7,57E-05 kg CO₂ eq is the most harmful environmental impact category. This work discussed the environmental implication of 1 kWh of electricity production from a natural gas conventional power plant. The LCA methodology used on natural gas for electricity production shows that the results depend on system boundaries, the data source and the technologies used. Further improvement on the environmental performance would require careful component selection for the right technology to allow mitigation. LCA shows that natural gas conventional power plant for electricity production is more environmentally friendly than other fossil fuels. The result of this study can be used as a guide for stakeholders involved in the environmental implication of plants and policymakers are bound to understand better how the electricity production from the natural gas conventional power plant is allocated. Also, the results of this study are relevant since natural gas is being promoted globally as a fuel source for electricity-producing plants.

Future studies will include a comparison of these results with other energy technologies. Comparison of different capacity sizes of natural gas power plants should consist of other indicators apart from Global Warming Potential, Freshwater Eutrophication Potential and Terrestrial Acidification Potential for impact assessment.