Life cycle assessment of Iran energy portfolio: Renewable energy replacement approach

Nowadays, due to the increasing energy demand in different industry, agriculture, and household sectors, great importance is attached to energy portfolio and generation/consumption in macrolevel planning. A viable approach to power generation planning is the environmental assessment of the power generation process. This study employs life cycle assessment based on Eco‐Indicator 99 methodology which analyzes midpoint and endpoint impacts. Energy impact evaluation is based on Eco‐invent database from resource harvesting to recycling. The study aims to assess Iran's energy production/consumption portfolio, but technical construction, operation, and recycling are not discussed. The study focuses on energy demand and energy generation resources in Iran, under three energy portfolio scenarios: (1) a basic scenario is a real energy portfolio for Iran's 2018‐power demand, (2) Iran's 2050‐energy portfolio with maximum accessible renewable energy capacity, and (3) Iran's 2050‐energy portfolio with zero‐carbon emission to evaluate the final consequences of life cycle. The York model is used to estimate energy demand in 2050. The Green‐X model is used to evaluate the relationship between the impacts and economic growth. Iran's energy portfolio has a low emission, compared with the global portfolio with a 36%‐coal application. Among Iran's portfolios, the most adventitious scenario is in 2018, followed by the 2050 portfolio with population growth and 50% increase in energy demand, and the zero‐carbon scenario with 64% of energy portfolio based on solar and wind energy technologies. Compared with the 2018 scenario, in the second and third scenarios, the environmental effects are decreased by 40% and 52%, respectively, indicating the significance of renewable energy in reducing the environmental consequences.


| INTRODUCTION
With the increase in studies and the need for energy, concepts like sustainable energy have attracted attention. Sustainable energy can be defined as a form of energy that can be used several times without subjecting the resources to the risk of depletion, expiration, or vanishing. 1 The recent uptrend in energy generation is the result of significant population growth and the development of industrial activities that have increased the need for electricity; according to the International Energy Agency, electricity generation has reached from 6098 million tons in 1973 to 14,282 million tons in 2019, 2 and this increase is threatening for the environment. For instance, infrastructural developments in thermal power plants that generate using fossil fuels and emit greenhouse gases and toxic material, which pollute water, soil, and air, endangering the ecosystem, human health (HH), and other creatures. The impacts of thermal power plants on the environment include an increase in temperature, greenhouse effects, acid rains, reducing agricultural activities, endangering HH, and disruption of the ecological balance. According to the studies, about 8.7 million premature births and one-fifth of the deaths in 2018 were due to air pollution. 2 However, the per capita energy consumption in developing countries is higher than in other countries and considering Iran's position, which is in the first half of Kuznets's environmental curve, destructive environmental impacts are much higher. Certainly, with a 5.2fold growth in energy output from 1990 to 2017, Iran's power plants play an essential part in the region's ecological effects. 2 According to detailed reports from Tavanir's Specialized Mother Company in 2018, 90% of the electricity generated in Iran is supplied by power plants that use fossil fuels as their raw materials; this means that the emission of polluting and destructive gases is higher than other power plants. [3][4][5] Today, with increased information about communities and awareness of managers, assessment of environmental impacts in industrial activities is one of the major discussions and concerns, and many planners of this context believe that the first essential step of the generation management process is an accurate assessment of environmental impacts 6 ; therefore, an accurate tool that can consider the effects of electricity generation and determine the physical boundaries of the plant is needed. Life Cycle Analysis (LCA) is a tool used to evaluate the environmental impacts that can calculate the generation to recycling chain while considering the potential diffusion of product/service. 7 LCA is a technique used to assess environmental aspects and potential impacts of the generation or service provision process. This method is based on three principles: collecting a list of energy inputs, materials, and emissions to the environment, assessment of potential environmental impacts with the defined inputs, and emissions to the environment, and interpreting the results to help decision-making. Therefore, LCA is a tool used to analyze the environmental impacts of the products during their life cycle, from extracting resources to material production, producing parts, and final production of the products and using the product for postdisposal management, including recycling, reusing, and final disposal. Determining the goals and plans is considered the key factor of the evaluation method and it is related to all of its components. In the finding analysis section, quantitative data like mass and energy balance of the input material and products and emission of the pollutants to air, water, and soil are identified for all studied processes, and they are used to modify the work goals and plans. In the evaluation of the life cycle method impacts, the processes are identified quantitatively and qualitatively, their impact indices are determined, and finally, these indices are evaluated considering their impact on the environment. 8 To this end, examining the current production and consumption status of Iran's electricity industry is necessary to better understand the problem.
In 2018, all urban population and 100% of all rural households with more than 20 households had access to electricity. This year, Iran's required electricity energy was supplied by power plants affiliated with the Ministry of Energy, large industries, and the private sector, including 25 steam power plants, 70 gas plants, 25 distributed generation units, 28 combined cycle power plants, 45 diesel power plants, 59 hydraulic power plants (large, medium, small, and mini), 270 wind turbines, 50 photovoltaic units, biogas power plants, and 2 thermal recycling power plants owned by the private sector. 9 Also, large industries have 5 steam power plants, and  This year, the strategy of the Ministry of Energy to increase the electricity generation capacity was to use the combined cycle power plants with new technology, higher efficiency, and lower pollution, using and developing renewable energies considering the increasing global hard-ships and the necessity of considering these ecofriendly energies, 10 increasing simultaneous heat and electricity generation to increase fuel efficiency and developing distributed generation power plants (power plants with less than 25 MW capacity), aiming to supply local consumption and reduce distribution network losses and achieve higher efficiency in electricity generation and less pollutant emission. To this end, the following actions were taken: this year, gas power plants were considered more than before due to their low price and short construction period, the possibility of increasing efficiency (by converting them to a combined cycle), and the possibility of constructing more main and side devices inside the country. To employ more gas and combined cycle power plants with advanced technology, higher efficiency, and lower pollution, the gas power plants owned 32.9% of the total capacity of all power plants in 2017, which decreased to 31.8% in 2018. On the contrary, the capacity ratio of the combined cycle power plants increased from 29.4% to 31.1%. A part of this increase is due to the strategy adopted by the Ministry of Energy to convert the gas power plants to combined cycle power plants to reduce greenhouse gas emissions and increase efficiency-one of the policies of the electricity sector of the National Energy Strategy Headquarter is to increase the portion of renewable and clean energies in the electricity generation capacity. The rated capacity of the renewable and modern power plants (wind, solar, biogas, and thermal recycling) increased 28.2% from 476.9 MW in 2017 to 611.5 MW in 2018. The share of wind, solar, biogas, and thermal recycling power plants in 2018 is 8% of the total capacity of the power plants.
While, according to the sixth law of socioeconomic development plan, the government had to reach the share of the renewable and clean power plants with the nongovernmental sector (domestic or foreign) being before a minimum of 5% of the total electricity generation by the end of this plan. In 2018, the development of hydraulic power plants has also been considered to generate electricity by constructing dams due to control floods, supply drinking, and agricultural water, reduce fuel consumption, be nonpollutant, easy operation, negligible domestic consumption, fast start and stop, network frequency control, negligible repair and maintenance cost, and the possibility of constructing power plant equipment inside the country, and their capacity has increased 75.1 MW compared with the previous year. According to the final plan, 1393 MW should be added to the capacity of the hydraulic power plant (including storage pump power plants) by 1401. Among policies of the electricity sector, increasing the simultaneous generation of heat and electricity, aiming to increase fuel efficiency, and developing distributed generation up to 3000 MW to supply local consumption and reduce distribution network loss can be mentioned. It has been considered to add 1152 MW to the generation capacity of the distributed generation units and simultaneous electricity and heat generation capacity by 1401. In the recent decade, the Ministry of Energy has done various activities to assign the existing power plants to the private sector and motivate the private sector for electricity generation. Considering the outsourcing and privatization policy in the electricity industry, the share of the private sector's power plants in recent years has increased in 2018. This study aims to evaluate the environmental effects of Iran's energy portfolio in its current state and provide alternative solutions based on the existing capacities and successful experiences such as the zero-carbon program of British Petroleum Company. For the first time, this study has obtained the environmental effects of electricity generation in Iran for the country's entire energy portfolio. Accordingly, by taking advantage of the net zero-carbon project objectives and using renewable energy capacities in Iran, solutions have been provided to reduce the environmental impacts of power generation in Iran, by calculating the amount of electricity demand in the next 30 years according to the population growth models.

| BACKGROUND
In 2018 in Iran, the total electricity sale of the Ministry of Energy and large industries (including electricity consumed by refineries, coking, and blast furnace units) increased by ∼10%, compared with 2017, and reached ∼2,628,362 GWh, 25,672,365 GWh (98.8%) of which was made by the Ministry of Energy and 3113.0 GWh of which was generated by large industries' power plants. Excess electricity generation by large industries is usually sold to the global network. Consumption management requires power optimization and shifting consumption from peak hours to other daily hours.
Household consumption: in 2018, Iranian household electricity consumption (mainly including lighting, home appliances, and cooling devices) was ∼29,600 kWh per capita, showing a 3.0% reduction compared with 2017. Commercial consumption: It averaged ∼4142.7 kWh (7.3%), showing a 0.9% reduction compared with 2017. [3][4][5][6][7][8][9][10][11] Public sector consumption: This represents 9.3% of the electricity sale of the Ministry of Energy in 2018, with an average consumption of ∼14,449.7 kWh per customer (decreased by 3.4% compared with 2017). Industrial consumption: 34.1% of the electricity sale of the Ministry of Energy in 2018 was for industries (88.5 TWh excluding transportation, increased by 1.5% compared with 2017). Larger industries had their power plants to supply part of their required energy.
Transportation sector consumption: Electricity is used as a green source in the transportation sector. In Tehran, Mashhad, Isfahan, Shiraz, and Tabriz, total electricity consumption in the transportation sector in 2018 was about 520.8 GWh, which increased by 9.3% compared with 2017.
Although the electric transportation share in 2018 was about 17 times greater than that in 2010, it was only 0.2% of the total power sold by the Ministry of Energy. The environmental impacts of electricity generation in Iran's energy portfolio were estimated using LCA based on 14040ISO and 14044ISO methods. [12][13][14] The SimaPro software package 15 was used to model power options and estimate the environmental impacts. 16 Energy system flexibility is foreseen as a strategy to integrate higher renewable share and reduce adverse events to the Power Grid. At the same time, the storage options for supporting high Renewable Energy Systems. 17 Alizadeh and Avami 18 employed the LCA approach to analyze environmental efficiency at the global level and used Exergo-Environmental Analysis (Eeva) at the power plant components level for Hellisheioi geothermal power plant, a combined heat power plant with an installed capacity of 303.3 MW for electricity and 133 MW for warm water. The analysis employs published data by reconciling the inventory to the last data-source, while comparing the life cycle impacts of three methods 19 (Midpoint2011 inventory life cycle data system [ILCD], Midpoint-Endpoint 2016 ReCiPe, 20 and CML-IA Baseline) for two scenarios. In scenario 1, any emission reduction system is considered. In scenario 2, CO 2 and H 2 S are reinjected. The analysis identified some main environmental impacts of power plants, like, acidification, suspended particles formation, ecosystem, and human toxicity. Eeva 17 identified wells as an important environmental factor in construction, operation, maintenance, and the end-of-life of an high pressure condenser as a component with maximum environmental cost rate.
Alizadeh and Avami (2020) 12-14,16-18,20-23 proposed a comprehensive framework to evaluate the performance of renewable and fossil power plants using LCA while considering free ecosystem services in system stability. The results showed that wind and photovoltaic power plants had the best performance, while wind and combined cycle power plants had the highest emergency stability index. The best scenario was selected using an optimization protocol with unit score and emergency stability as goal functions. Wind power plant was the most attractive option, followed by combined cycle power plant with low CO 2 absorption. Eco-Indicator 99 and CML 2001 were used to evaluate the effects of midpoint and endpoint. SimaPro and GaBi software were mainly used.
Bhandari et al. 24 analyzed the global warming potential (GWP) in wind power plants under the LCA framework. Secondary data were evaluated using wind turbine studies published in the last 20 years. Data fell into three categories: single onshore turbines, onshore wind farms, and offshore wind farms. In a multivariate analysis using the linear regression model, the data sets extracted from the literature were evaluated using SimaPro and mathematical equations based on Ecoinvent V.3.6. On the basis of the results, as the dimension of wind turbine increases, CO 2 emission decreases.
Shah and Unnikrishnan 25 studied a 655-MW-capacity power plant in India with a combined cycle and gas as its fuel using LCA. Considering all upstream and immediate processes inside the plant and excluding the transmission and distribution losses, waste management, power plant construction, and destruction, they assessed and categorized the environmental impacts into 12 general groups using GaBi and CML 2001.
Usapein and Chavalparit 26 implemented LCA as a generation unit in Thailand with an electricity generation efficiency of 53% and heat generation efficiency of 80%. They categorized the environmental impacts into 14 groups (climate change, ozone depletion [ODP], carcinogenesis, photochemical ozone formation, atrophy, and fossil resources depletion) and estimated the life cycle environmental impacts using ILCD. They discriminated extraction, natural gas transmission, natural gas processing, and electricity generation steps in power plants to calculate PM, NO X , and SO 2 emissions from combustion relations of CO 2 directly as output pollutants. These values were reported without normalization and weighting, indicating that fuel combustion and natural gas extraction have the maximum environmental impacts. The direct impact share of the power plant in the climate change category was estimated to be 88%, while the share of natural gas extraction was 11.7% and the share of other processes was below 1%. In the ODP category, these values changed such that the natural gas extraction share was 1.67%, while in human toxicity category, the maximum environmental impacts were related to fuel combustion.
Brizmohun et al. 27 assessed the life cycle of different power plants in Mauritius by examining coal, furnace oil, hydraulic power, and sugarcane electricity generation. The extraction and production of fuel, power, and its distribution/transmission to the consumption site were fully and partially explored, and the transportation step in the waste management was also considered. The CML Baseline2001 and SimaPro were used to assess the environmental impacts. The maximum negative impacts of coal power plants were associated with global warming, nonbiological resources depletion, atrophy, and ecosystem toxicity. In power plants with furnace oil fuel, maximum negative impacts pertained to acidification, human toxicity, photochemical ozone formation, ODP, and ecosystem toxification. Hydroelectric power plants performed desirably in most categories.
In 2015, Atilgan and Azapagic 28 studied fossil fuel power plants (coal and gas) in Turkey. Using various measures (e.g., acidification, global warming, nonbiological resource depletion, and photochemical ozone formation), they examined the environmental consequences of fuel extraction, processing, transmission, combustion, construction, and end-of-life in power generation in power plants using CML 2001 and GaBi. Among the 11 categories considered in their study, electricity generation from natural gas has the minimum environmental impact, but its ODP is 48 and 12 times the ODP of power plants with coal and hard coal fuel, respectively. The maximum impact is associated with intraplant operations and transportation. The role of construction and salvage steps was negligible. The results showed that recycling material after salvage does not play a significant role. Besides, recycling material after power plant salvage decreases the impact by 1%.
In 2015, Ramirez et al. 29 in Ecuador evaluated the life cycle impacts of steam power plants and internal combustion engines with furnace oil fuel. Life cycle boundaries were assumed as fuel extraction, refining, preparation, producing chemical substances, manufacturing parts, power plant construction, waste and swage recycling and refinement, and other power plant operations. Data were collected from three steam power plants and two internal combustion engine power plants. The results revealed that internal combustion engine power plants perform better in abiotic depletion potential (ADP), global warming, ODP, photochemical ozone formation, and acidification. The maximum share of environmental impacts was related to global warming, photochemical ozone formation, acidification, and atrophy. From the life cycle boundaries, fuel production, extraction, and refining played a major role in increasing ADP and ODP.
In 2014, Agrawal et al. 30 assessed the life cycle of a combined cycle power plant with natural gas fuel in India with a capacity of 350 MW. The impact categories were introduced by depicting the upstream and operational processes of the power plant. Global warming, acidification, atrophy, ecosystem toxification, carcinogenesis, climate change, and inhaling organic and nonorganic material were considered using SimaPro, Eco-Indicator 99, and CML 2001. Maximum impacts were caused by upstream processes excluding global warming and inhaling nonorganic material. Carcinogenesis (81%) and inhaling organic material (88%) also had the maximum impacts. This might be due to extraction, processing, and transmission of fuel and chemical substances during which pollutant gases are released. The human body toxification capacity affects HH by 47%, while the climate change capacity affects HH by 53%.
A study in Mario Molina Center in Mexico (2013), 31 considered eight power plants: combined gas power plant, combined gas cycle power plant, coal power plant, coal power plant, nuclear power plant, wind power plant, geothermal power plant, and a small hydroelectric power plant. Life cycle steps were: fuel extraction, refinery, and transmission, power plant construction, intraplant operations, and waste management. The impacts were categorized as ADP, acidification, climate change, ODP, and atrophy; SimaPro and CML 2000 were used. The results proved that power plants with fossil fuel and coal have the maximum environmental impact, while the combined cycle power plants without CCS have the maximum environmental impact. Adding CCS also plays a significant role in GW increase, such that its impact in coal and combined cycle power plants is 86% and 87%, respectively.

| Goals and domain
The main goal of this study is to estimate the environmental impacts of the life cycle of electricity generation using different energy generation systems and replacing renewable energy with fossil fuels in the power plants. 19 To this end, the base portfolio is Iran's 2018 energy portfolio.
• The operational unit is considered. • The energy generation operational unit generates 1 kW electricity. • The annual electricity generation in 2018 was 2,628,362 GWh, and per capita consumption is used for comparison. 3 As shown in Figure 1 for thermal power plants with 1 kW output, Figure 2 for nuclear power plants with 1 kW output, Figure 3 for photovoltaic power plants with 1 kW output, and Figure 4 for wind power plants with 1 kW output, the life cycle of a power plant is comprised of three main phases, including construction, operation, and end-of-life. Since the information on the construction, and end-of-life of the power plants is not available and the lifetime of a power plant is more than 30, these two phases are neglected. However, databases can be used, but it is preferred not to introduce many uncertainties into the model. In previous studies, it has been mentioned that the impacts of these two phases are negligible. Fuel and raw material extraction is also ignored due to the same reason. It should be noted that the impact of these phases is very small compared with other phases. 22 The study scope for all electricity options is from cradle to grave, including the following life cycle steps: electricity generation operations, power plant construction, and salvage at the end of their life.

| Energy consumption
With the introduction of the psychology concept by Keynes, 34 the relationship between income and consumption costs became a key relationship in macroeconomic analyses. Also, Friedman, in the permanent income hypothesis (PIH), suggests that consumption in a given year does not depend on the income of the individual in the same year, but depends on the permanent income or expected income of the individual.
Thus, he divides the individuals' income into permanent and temporary incomes. Temporary income is sometimes positive and sometimes negative, which neutralize each other in long term. Thus, savings preserves the consumption at the permanent consumption level. Followed by this theorem, Modigliani 35 introduced the permanent income in the Life Cycle Hypothesis theorem framework. According to this theorem, the purpose of the consumer is to maximize the favorability resulting from consumption considering the financial resource constraints. This theorem, like, PIH, is based on society's wealth and its efficiency based on which the consumption level is determined. However, inference in the context of PIH is different. Modigliani divides the life cycle of individuals into three periods: childhood (below 14 years old) in which consumption is higher than income, and adulthood (15-64 years old) which covers the middle years of an individual's life and is considered as the generative years of an individual. During this period, consumption is lower than an individual's income, a part of which is used to repay the debts, and a part of it is saved. The third period is the elderly (above 65 years) in which the individual's consumption exceeds his/her income.
Therefore, in this section, the York model 36 is used and the consumption life cycle and Kuznets's environmental curve are integrated to estimate the following model with a panel econometric approach for Southwest Asian countries.
E it per capita energy consumption of the countries, G it per capita generation of the countries, P it the total population of the country, U it the urban population ratio, P YO it percentage of the individuals below 14 years and above 64 years (determining the age structure of the population).
To prevent collinearity relationships in the model, the following variables, related to the age structure of the population, are introduced independently in the model. As shown in Table 1 the age distribution in 2020.

| Power plant fuel data of Iran
The  Table 2

| Renewable energies
Renewable energy, often known as clean energy, is derived from natural sources or processes that are constantly regenerated. This sort of energy harnesses the power of nature to provide warmth, transportation, electricity generation, and so forth. The absence of greenhouse gases and contaminants makes this energy superior to fossil fuels. Renewable energy sources provided 13.8% of the world's primary energy generation (including source energy) in 2017. Given the potential capacity of the renewable energy sector, Iran can serve as a regional hub for the development of this sort of energy. As shown in Table 3

| Research scenarios
First, calculate the amount of energy generated and consumed based on the available data from the energy balance sheet, and then, using the York model, calculate the amount of energy demand for 2050 using the software that is included. In this section, all of the impacts are evaluated and compared using the strategy of reducing environmental impacts. In this context, the following research evaluation scenarios will be used: • Evaluating the environmental impacts of Iran's life cycle in 2018. • Evaluating the impacts considering the available renewable energy capacities of Iran in 2050. • Zero-carbon energy portfolio till 2050. 39

| Energy demand in 2050
According to statistical data, population growth rate, and mortality rate in Iran, the status of Iran's age distribution in 2050 is illustrated in Table 4, 37 which uses World Information Bank statistics and achieves a growth rate of 24.2 years up to 2050. According to Business Monitor, Iran's population will grow to 103 million by 2050, increasing demand in the energy sector.
According to the above description and the York model, one method is to calculate the amount of energy consumption demand in which various factors such as population growth, urban population, age distribution, and income are effective, and the parameters used in the model are calculated using World Bank 37 calculations and information, as shown in Table 5.
According to the projections, Iran's per capita energy demand in 2050, with a population of 103 million, is 3640 kWh, compared with 3072 kWh in 2018.
According to the above information, Iran's energy demand in 2050 will be 374,444 GWh/year, and the results are shown in Table 6.
This means an annual consumption growth rate of 1.4% on average. In another study, the annual consumption increase for global consumption is expected to be around 2% by 2050, thus this study utilizes per capita consumption in the remainder of the analysis.

| Life cycle analysis
The Eco-invent 3 database 39 is used to determine the number of environmental impacts generated by the generation of 1 kWh of energy, the index raw materials are used as inputs to measure the size of the power plant unit and their transportation.

| Inventory analysis
The wind power plant is comprised of four sections: blades, generator, control section, and gearbox. 40,41 The life cycle assessment inputs are given in Table 7. To generate 1 kW of electricity from solar panels, you can refer to Table 8. This study assumes the usage of a multicrystalline panel and a 2.5-kW inverter, the impacts of which are typically detailed in the database.
The next technology is hydroelectricity technology, which has the maximum share in renewable energies of the current portfolio, and the main impact of this power plant is in its construction and operation steps because of constructing fortifications and installing power plant seal, Table 9 contains data of 1 MW hydroelectric power plant.
The fossil fuel section deals with the inputs of gas and oil power plants, which account for the majority of Iran's energy portfolio. Due to a large amount of gas and oil reserves in Iran, these two technologies account for around 85% of the electrical supply portfolio. Tables 10 and 11 show the life cycle assessment inputs of these two power plants.

| Middle impacts using Eco-Indicator 99 method
In this method, middle impacts are calculated, 54,55 which include carcinogenesis, inhaling organic and nonorganic compounds, climate change, radiation, ozone depletion, and ecosystem damage, acidification, and atrophy, resulting in the end impact of ecosystem quality and, eventually, land occupation, depletion of mineral and fossil resources, which results in the end impact of resource depletion, for which the Eco-invent 3 database in SimaPro software is utilized. Table 12 displays the outcomes of its middle impacts. In this regard, Table 13 shows the end impacts, which comprise HH, ecosystem quality, and resource depletion in a normalized manner. Figure 5 shows a comparison of power plant fuels. As can be seen, three fossil fuels have the greatest impact on HH, whereas hydropower, wind, and solar energies have the least impact. However, geothermal power plants have the greatest impact on the quality of life of any renewable fuel. Finally, three fossil fuel power plants have the maximum impacts, solar, nuclear, and hydropower plants have the minimum impacts, and when considering the impacts of resource depletion, three fossil fuel power T A B L E 8 Inputs of a 1-MW photovoltaic power plant. 45

| Comparing Iran with demand approach in 2050
Because the analysis in this section pertains to the end and middle impacts of various technologies and their emission for energy supply. On the basis of the calculations in this study, Iran's energy demand in 2050 with 103 million people is 3640 kWh, which is comparable to 3072 kWh in 2018. According to the above information, Iran's energy demand in 2050 will be 374,444 GWh/year. In this section, the environmental impacts of the life cycle in 2018 are examined and compared with those in 2050. The share of energy generation utilizing per capita consumption is provided in Table 14.
In the following, the end impacts of the life cycle of Iran's 2018-and 2050-energy portfolios are investigated. As concluded in this section, the end impacts of the 1-MW generation life cycle, which is given in Figure 6 to display the same results.
As a result, in the energy portfolio scenario, the maximum capacity of the renewable energy portfolio is compared with the current energy portfolio. Figure 7 compares the impact of fossil fuels in two portfolios, whereas Figure 8 compares the impact of HH in two portfolios for renewable energy. The majority of the impact is still on fossil fuels, specifically gas fuels, due to high usage accounting for around 38% of the energy portfolio. The majority of the changes, on the other hand, are related to solar and wind energy.
The next issue is the ecology quality, which is depicted in Figures 9 and 10, where the largest changes are related to wind energy, which has an index of 317 in the discussion of renewable fuels, followed by hydroelectric power and solar power.
And, in terms of fossil fuels, the percentage of gas usage remains the highest, followed by oil.
The third impact is resource depletion, which is depicted in Figures 11 and 12. In the subject of renewable energy, the greatest changes are related to solar energy, followed by wind and geothermal energy.
As seen, changes in the energy portfolio, if directed at replacing fossil fuels, can greatly decrease the impacts, that is, as noted in the above discussion, the share of gas fuels is 38% of the portfolio, and the share of wind and solar energy is 10% and 15% of total generation, respectively. However, gas fuel is four times more effective than wind energy in terms of energy supply, but the impacts of gas on the wind are significantly different, that is, the end impact of gas fuel on HH. HH has a 56-times impact on wind energy, and the impacts on ecosystem quality and resource depletion are 46-times and 45-times, respectively. The values for HH, resource depletion, and ecosystem quality for gas fuel and solar energy of the power plants are 53, 57, and 47, respectively. This suggests that the number of emissions produced by solar and wind technologies may be greatly reduced to achieve the objective of sustainable energy.
In this study, as shown in Figure 13, the rate of changes owing to the new energy portfolio for end impacts of the life cycle decreased by 49%. This means that by reducing the percentage of fossil fuels, solar energy will cover 15% of the energy portfolio and wind energy will cover 10% of the energy portfolio, and the environmental impacts might be reduced by one-third.

| Perspective in the energy portfolio
According to the Energy Transmission Commission, plans to decrease global carbon emissions to zero by 2050 will cost between $1 trillion and $2 trillion per year T A B L E 11 Inputs of a 1-MW oil power plant. 51 (about 1.5% of the world's gross domestic product). The results of this scenario are illustrated in Figure 14 and the ETC has recommended three methods for achieving zero-carbon emissions: • With major advances in energy efficiency and a shift to a rotating economy, developing economies can use less energy while raising their living standards. • Increasing clean energy supply by mass-producing clean energy capacity at a rate 5-6 times faster than today. • Use of clean energy in all sectors of the economy through a variety of applications in buildings, transportation, and industry, as well as the implementation of new technologies and processes based on hydrogen, sustainable biomass, or carbon sequestration in sectors that cannot be electrified, such as heavy industry, like, aviation.
The utilization of renewable energy, as described in the second proposal, is an important aspect of reaching the zero-carbon debate. In the rest of the study, the total renewable energy capacity is mentioned and LCA for supplying energy in a zero-carbon state is described. Iran has a capacity of 100,000 MW for solar energy generation F I G U R E 9 Impact of ecology quality on fossil fuels used in power plants for energy supply in 2018.
F I G U R E 10 Impact of ecology quality on renewable energy power plants in terms of per capita energy supply in 2018.
F I G U R E 11 Impact of resource depletion on fossil fuel of the power plants to supply per capita energy in 2018.
F I G U R E 12 Impact of resource depletion on renewable energy power plants to supply per capita energy in 2050. and 40,000 MW for wind energy generation. This work can supply the peak of the day from solar energy and the peak of the night from wind energy. In other words, despite having 140,000 MW of God-given capacity to generate electricity from wind and solar, this study has not yet reached 1000 MW in this area. On the other hand, based on the findings of this study and per capita consumption in 2050, the peak consumption will be 79,000 MW. By 2050, the share of solar and wind energy consumption in total global power generation is predicted to rise to 35% in the base scenario, 55% in the rapid transition scenario, and 64% in the zero-carbon scenario. Then, using Eco-invent 3 databases and SimaPro software, the study has proceeded onto the rest of the environmental impacts and analyzed the impacts of energy generation for various fuels. The study has used the CLM approach for the middle impacts and the Eco-Indicator 99 method for the end impacts in this part. Then, considering the per capita energy consumption in 2018, Iran's energy portfolio was extended using two scenarios. The first scenario involves the use of existing capacity in Iran's energy development plan, while the second involves the use of a zero-carbon-dioxide share of BP, Iran's energy portfolio in 2018 and 2050 in terms of population growth, economic growth, and demand. The relevant impacts are investigated, as discussed in the evaluation of these three portfolios below.

| Comparative results
As shown in Figure 15, the end impacts of the three scenarios are compared, beginning with the most adventitious scenario for the energy portfolio in 2018, followed by the energy portfolio in 2050, which takes into account population growth as well as a 50% increase in energy demand, and finally, the zero-carbon scenario, which uses both solar and wind energy technologies for 64% of the energy portfolio. The average difference between the impacts of 2050 and the origin year of 2018 is around a 40% reduction of impacts, and for the zerocarbon scenario compared with the portfolio of 2018, the impacts are reduced by approximately 52%. The greenest portfolio is the zero-carbon scenario, and it has a 22% lower impact than the 2050 basket.

| CONCLUSION
The most significant factor in the generation is the market demand for a product. Throughout history, one of the most pressing human problems has been energy supply and it will continue to be. This energy supply is now done more intelligently. Proper energy supply planning is one of the priorities of any society. The introduction of a realistic vision for the future is required for proper planning for sustainable growth. This picture of the future is reflected in the amount of energy demand as well as the state of available resources in the energy sector. This study has sought to investigate energy demand to obtain an accurate picture of future energy portfolio output. Energy demand will be different in 2018, with a population of roughly 82 million, compared with 2050. In this regard, energy consumption in 2050 was calculated using population and income models, which is one of the strategies described in Section 3 of the York model, which is influenced by factors, such as population growth, urban population, age distribution, and income. According to Section 4, Iran's per capita energy consumption in 2050 with 103 million people will be 3640 kWh, which is comparable to 3072 kWh in 2018. That means overall power consumption will rise from around 253,000 to 374,000 Giga tons over the next 30 years, reflecting a 47% increase over 30 years and a 1.4% annual growth rate, resulting in an 18% increase in per capita consumption Various impacts were considered to investigate life cycle assessment, for example, the impact of carbondioxide emissions in the form of the impacts of global warming in a particular technique, where this group involves other factors, such as methane emissions, and so on. In Section 4, the remaining environmental impacts were investigated using Eco-invent 3 database and SimaPro software and analyzed the impacts of energy generation for various fuels. The CLM approach was used for the middle impacts and the Eco-Indicator 99 method for the end impacts based on the results of this section. Then, considering the per capita energy F I G U R E 15 Comparison of the studied scenarios. consumption in 2018, the impacts were investigated. Concerning population growth, economic growth, and demand, the first scenario was expanded by using the current capacity in Iran's energy development plan and the second scenario by using the BP zero-carbon project, to examine Iran's energy portfolio in 2018 and 2050. Moreover, the impacts were obtained, as discussed in the following.
The Eco-Indicator 99 approach was used to discuss the end impacts, which first employs middle impacts, such as carcinogenesis, inhaling inorganic and organic compounds that calculate the end impact of HH, climate change, radiation, acidification, ozone depletion, ecosystem toxicity, and atrophy, which eventually leads to the end impacts of ecosystem quality, land occupation, depletion of mineral and fossil resources, which ultimately leads to the end impact of resource depletion. The results of this approach are reported to be convergent with the results of the previous method. In general, fossil fuels have the maximum impacts and have the maximum impact on HH, followed by resource depletion and, ultimately, ecosystem quality.
The first scenario investigates Iran's energy portfolio in 2018 using Tavanir Company statistics and the outcomes of the impacts, finding that fossil fuels, and natural gas account for around 91% and 78% of Iran's electricity generation, while renewable energy sources such as solar, wind, and geothermal account for less than 1%.
The second scenario studied Iran's energy portfolio with the maximum available capacity of renewable energy, in which the percentage of natural gas is decreased to 38%, and the contribution of renewable energy for solar energy, wind energy, and hydroelectric power is reduced to 15%, 10%, and 29%, respectively.
The third scenario, developed from the zero-carbon program, has the highest percentage of solar and wind technologies, accounting for 64% of the entire portfolio.
To compare the end impacts of these three scenarios, with Iran's 2018 energy portfolio being the most adventitious one, followed by the energy portfolio in 2050, taking into account population growth as well as a 50% increase in energy demand, and finally, the zerocarbon scenario, which is 64% of the energy portfolio from both solar and wind energy technologies, the impacts of the second scenario compared with the first scenario are reduced by 40% and the impacts of the third scenario, which is the zero-carbon scenario, compared with the first scenario are reduced by 52%.
The most effective portfolio is the first scenario portfolio, which depicts Iran's electricity generation portfolio in 2018, and this indicates the vacuum of sustainable management of electricity generation, and according to the contents of Sections 3 and 4, using the maximum current energy capacity of hydroelectric power, solar, and wind power plants to reduce the environmental impacts on HH in the first stage, and then God-given resources and ecological quality up to 40%. It is also hoped to further reduce the environmental impacts considering the available capacities and diligent youth for energy generation management. [56][57] ORCID Abolfazl Ahmadi http://orcid.org/0000-0003-2652-6011