Technical economic and environmental analysis of Chemical Looping versus oxyfuel combustion for NGCC power plant

Technical Economic and Environmental analysis of Chemical Looping versus oxyfuel combustion for NGCC power plant Pietro Bartocci1,2, Alberto Abad1, Arturo Cabello1, Mauro Zampilli2, Giulio Buia2, Angela Serra3, Simone Colantoni3, Andrea Taiana3, Gianni Bidini2, Francesco Fantozzi2 1Instituto de Carboquímica (ICB-CSIC), Miguel Luesma Castán 4, 50018, Zaragoza, Spain 2Department of Industrial Engineering, University of Perugia, Via G. Duranti 67, 06125 Perugia, Italy 3Baker Hughes, Piazza Enrico Mattei, 50127 Firenze, Italy Abstract. The Power Sector is undergoing a rapid technological change with respect to implementation of low carbon technologies. The IEA Energy Outlook 2017 shows that the investments in Renewables for the first time are equal to those on the fossil sources. It is likely that the conventional gas turbines and internal combustion engines will need to be integrated in systems employing biofuels and/or CCUS (Carbon Capture Usage and Storage). Also, the European Union is moving rapidly towards low carbon technologies (i.e. Energy Efficiency, Smart Grids, Renewables and CCUS), see the Energy Union Strategy. Currently 28% of the installed power capacity in Europe is based on natural gas plants. Gas-based power capacity has reached 418 GW in 2016 and is likely to continue to grow in the future. To efficiently capture the carbon dioxide emissions generated by the combustion of natural gas in the combustion chamber a possible solution could be to adopt new combustion processes, like Chemical Looping Combustion. The combination of CLC and GTs can decrease the efficiency of a combined cycle power plant from 60% to about 40.34%. These performances influence costs and environmental burdens and this is also the same for oxyfuel combustion, which is a competing technology to realize CCS. This paper, starting from literature mass and energy balances of a conventional combined cycle, a combined cycle coupled with chemical looping combustor and a combined cycle coupled with oxyfuel combustion, calculates the reduction of CO2 emissions which can be achieved during the whole life cycle of the power plant and then identifies the value of the carbon credit which is needed to have an interesting payback period for such kind of investment. 1 Introduction The Power Sector is undergoing a rapid technological change with respect to implementation of low carbon technologies. The IEA Energy Outlook 2017 showed that the investments in Renewables for the first time are equal to those on the fossil sources [1]. For this reason, it is likely that the conventional gas turbines and internal combustion engines will need to be integrated in systems employing biofuels and/or CCUS (Carbon Capture © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI Usage and Storage). Also the European Union is moving rapidly towards low carbon technologies (i.e. Energy Efficiency, Smart Grids, Renewables and CCUS), see the Energy Union Strategy [2]. Currently 28% of the installed power capacity in Europe is based on natural gas plants [3]. In 2018 the installed CC plants had a capacity of 132.6 GW in the EU28 [1]. Power plants based on only gas turbines had a capacity of 15.9 GW and power plants based on only steam turbines had a capacity of 129.7 GW [1]. To efficiently capture the carbon dioxide emissions generated by the combustion of natural gas in the combustion chamber a possible solution could be to adopt new combustion processes, like Chemical Looping Combustion. Italy in particular has more than 57 NG power stations and a total capacity of about 40 GW [5] (which is in great part contained in the World Power Plants Database [6], which covers about 98% of the installed capacity). We see from [6] that 89% of the total NG power plants are represented by NGCC, 3% are represented by Integrated Gasification Combined Cycles (IGCC) and 8% are represented by gas turbines. CLC it is a form of unmixed combustion which uses an oxygen carrier to transfer oxygen from air to fuel. Thus the combustion products, CO2 and H2O, are obtained in a separate gas flow, see Figure 1, and H2O is easily removed by condensation. In this way, the carbon dioxide (CO2) is kept separate from the nitrogen in the air, and no energy is needed to capture the CO2, because air and fuel are never mixed. Fig. 1. Chemical Looping Combustion (CLC) technology The combination of CLC and GTs can decrease the efficiency of a combined cycle power plant from 60% to about 40.34% [7]. This implies the need of more natural gas to be burned to maintain the same electricity production. Also investment costs are likely to increase for this kind of plants. We can consider that the combustion chamber accounts for 11% of the total investment in the turbine [8] and that the investment for a pressurized fluidized bed combustor can range between 2140 - 5700 $/kW [9]. Based on these economic figures a complete financial analysis of the investment required for a conventional CC power plant and a CC with CLC power plant is performed. In the economic analysis a sensitivity analysis on the price of the carbon credit is performed to understand at what price the investment becomes interesting. Besides this a complete analysis of the life cycle of the two power plants is performed to understand if the loss of efficiency of the plant using the chemical looping combustor affects the environmental performances. Then using the EnergyPlan software the large2 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI Usage and Storage). Also the European Union is moving rapidly towards low carbon technologies (i.e. Energy Efficiency, Smart Grids, Renewables and CCUS), see the Energy Union Strategy [2]. Currently 28% of the installed power capacity in Europe is based on natural gas plants [3]. In 2018 the installed CC plants had a capacity of 132.6 GW in the EU28 [1]. Power plants based on only gas turbines had a capacity of 15.9 GW and power plants based on only steam turbines had a capacity of 129.7 GW [1]. To efficiently capture the carbon dioxide emissions generated by the combustion of natural gas in the combustion chamber a possible solution could be to adopt new combustion processes, like Chemical Looping Combustion. Italy in particular has more than 57 NG power stations and a total capacity of about 40 GW [5] (which is in great part contained in the World Power Plants Database [6], which covers about 98% of the installed capacity). We see from [6] that 89% of the total NG power plants are represented by NGCC, 3% are represented by Integrated Gasification Combined Cycles (IGCC) and 8% are represented by gas turbines. CLC it is a form of unmixed combustion which uses an oxygen carrier to transfer oxygen from air to fuel. Thus the combustion products, CO2 and H2O, are obtained in a separate gas flow, see Figure 1, and H2O is easily removed by condensation. In this way, the carbon dioxide (CO2) is kept separate from the nitrogen in the air, and no energy is needed to capture the CO2, because air and fuel are never mixed. Fig. 1. Chemical Looping Combustion (CLC) technology The combination of CLC and GTs can decrease the efficiency of a combined cycle power plant from 60% to about 40.34% [7]. This implies the need of more natural gas to be burned to maintain the same electricity production. Also investment costs are likely to increase for this kind of plants. We can consider that the combustion chamber accounts for 11% of the total investment in the turbine [8] and that the investment for a pressurized fluidized bed combustor can range between 2140 - 5700 $/kW [9]. Based on these economic figures a complete financial analysis of the investment required for a conventional CC power plant and a CC with CLC power plant is performed. In the economic analysis a sensitivity analysis on the price of the carbon credit is performed to understand at what price the investment becomes interesting. Besides this a complete analysis of the life cycle of the two power plants is performed to understand if the loss of efficiency of the plant using the chemical looping combustor affects the environmental performances. Then using the EnergyPlan software the largescale impact of the proposed technology is evaluated relatively to the Italian Energy System. 2 Materials and Methods 2.1 Chemical Looping Combustor: costs and impact Much research has been done on the optimization of the configuration of CLC burners when coupled with NGCC plants. For example, in the work of Khan [10] an interesting concept plant in which CLC is integrated with NGCC is proposed. The paper tries to reduce the energy penalty which is due to the fact that when integrated into a natural gas combined cycle (NGCC) plant, the CLC combustor works at a maximum achievable reactor temperature which is far below the firing temperature of state-of-the-art gas turbines. The proposed plant circumvents this limitation via an added combustor after the CLC reactors; in this way, a standard gas turbine can be deployed, and CO2 avoidance costs are reduced to $60.3/ton, mainly due to a reduction in the energy penalty to only 1.4%-points [10]. However, due to the natural gas combustor which is added after the CLC reactor, CO2 avoidance is only 52.4% [10]. Achieving high CO2 avoidance requires firing with clean hydrogen instead, increasing the CO2 avoidance cost to $96.3/ton when a hydrogen cost of $15.5/GJ is assumed [10]. A simplified scheme of a NGGT with a coupled Chemical Looping Plant is shown in Figure 2. In figure 2 we see that the fuel reactor (where reduction happens) and the air reactor (where oxidation happens) are interconnected. The air used to oxidise the oxygen carrier is previously compressed and then after exiting the air reactor it expands in the gas turbine. In a simplistic way the process can be considered similar to an external combustion gas turbine where the heat exchanger between exhaust combustion gases and air is missing. Fig. 2. Coupled NGGT and CLC combustor Such a plant has the following characteristics: - costs are about: 0.1 M€/MW; costs are mainly evaluated based on pressurized fluidized bed costs; 3 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI - the plant duration is estimated to be 30 years; Fan et al. 2018 [11] have performed an interesting study on the Life Cycle Assessment (LCA) of CLC plants coupled to CC fed with natural gas. They have studied the influence on the final impact of 4 technical factors: the type of oxygen carrier, its life, the environmental impact caused by the production of the oxygen carrier and also the thermodynamic performances of the technology. It was noted in [11] that the environmental impact is strongly dependent on the plant thermodynamic efficiency and from this perspective is more interesting to use a combined cycle with a pressurised CLC reactor than an atmospheric reactor which can be coupled only to a steam turbine and has a lower efficiency. Besides this the duration of the oxygen carrier affect also in an important way the environmental impact of the plant. In fact, the oxygen carrier is interested by attrition and reactivity losses. To avoid that the oxygen carrier duration has a negative impact on the environment a duration of 4000 hours is suggested by the authors [11]. The basic data which is necessary to characterize the technology by an environmental and technical point of view are proposed in table 1, taken from [11]. Table 1. Technical parameters CLC plant (800 MW plant) [11]. Stage Material Value Unit Plant Construction Concrete 128.25 t/MW Steel 40.9 t/MW Aluminium 0.4 t/MW Iron 0.4 t/MW Plant operation NG flow 1 kmol/s OC Flow 5988 kg/s OC Duration 1315 h An interesting information presented in the table 1 is the Oxygen Carrier (OC) duration we can see in fact that the iron oxygen carrier is assumed to last for about 1315 hours, while if we consider the nickel oxygen carrier this can last up to 10,000 hours. In the choice of the oxygen carrier it has also to be taken into consideration the price of the oxygen carrier and also its availability and impact (for example nickel carbon footprint is about 11.4 kgCO2eq/kg versus the 1.16 kgCO2eq/kg iron) [11]. 2.2 Comparison of net electrical efficiencies, of competing technologies: Chemical Looping Combustion, Hydrogen Combined Cycle and Oxyfuel NGCC Singh et al. 2011 [2] present an interesting work on Comparative life cycle environmental assessment of Carbon Capture and Storage (CCS) technologies. They analyse in particular two fuels: coal and natural gas. For each of them three solutions are taken into account: 4 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI - the plant duration is estimated to be 30 years; Fan et al. 2018 [11] have performed an interesting study on the Life Cycle Assessment (LCA) of CLC plants coupled to CC fed with natural gas. They have studied the influence on the final impact of 4 technical factors: the type of oxygen carrier, its life, the environmental impact caused by the production of the oxygen carrier and also the thermodynamic performances of the technology. It was noted in [11] that the environmental impact is strongly dependent on the plant thermodynamic efficiency and from this perspective is more interesting to use a combined cycle with a pressurised CLC reactor than an atmospheric reactor which can be coupled only to a steam turbine and has a lower efficiency. Besides this the duration of the oxygen carrier affect also in an important way the environmental impact of the plant. In fact, the oxygen carrier is interested by attrition and reactivity losses. To avoid that the oxygen carrier duration has a negative impact on the environment a duration of 4000 hours is suggested by the authors [11]. The basic data which is necessary to characterize the technology by an environmental and technical point of view are proposed in table 1, taken from [11]. Table 1. Technical parameters CLC plant (800 MW plant) [11]. Stage Material Value Unit Plant Construction Concrete 128.25 t/MW Steel 40.9 t/MW Aluminium 0.4 t/MW Iron 0.4 t/MW Plant operation NG flow 1 kmol/s OC Flow 5988 kg/s OC Duration 1315 h An interesting information presented in the table 1 is the Oxygen Carrier (OC) duration we can see in fact that the iron oxygen carrier is assumed to last for about 1315 hours, while if we consider the nickel oxygen carrier this can last up to 10,000 hours. In the choice of the oxygen carrier it has also to be taken into consideration the price of the oxygen carrier and also its availability and impact (for example nickel carbon footprint is about 11.4 kgCO2eq/kg versus the 1.16 kgCO2eq/kg iron) [11]. 2.2 Comparison of net electrical efficiencies, of competing technologies: Chemical Looping Combustion, Hydrogen Combined Cycle and Oxyfuel NGCC Singh et al. 2011 [2] present an interesting work on Comparative life cycle environmental assessment of Carbon Capture and Storage (CCS) technologies. They analyse in particular two fuels: coal and natural gas. For each of them three solutions are taken into account: capture in post combustion; capture in pre-combustion and capture through oxyfuel combustion. In this paper we take into consideration the results of the base case, so conventional NGCC, as shown in table 2, and also the results of the oxyfuel combustion (oxy-NGCC). Application of oxyfuel combustion in power plant implies reduction in net efficiency due to energy requirement of the air separation unit (ASU). In the natural gas oxyfuel combustion system, an efficiency loss of 11.3% can be assumed [13], due to energy allowance for ASU. In table 2 the 4 cases of interest are considered: the baseline case is represented by conventional NGCC plant (representative also of the Italian CC plants); the CLC combustor integrated with a NGCC, the pre-combustion CCS (see H2-CC), the oxy-combustion CCS (see oxy-NGCC). Table 2. Electrical efficiency, CO2 capture efficiency and energy penalty of different Combine Cycle upgrading technologies. Stage Electrical Efficiency CO 2 capture Efficiency Energy Penalty Source NGCC 58.1* 0% 0% [2] CLC-NGCC 45.7 % 97% 12.4% [11] H2-CC 57.7% NA 0.4% [14] Oxy-NGCC 46.8% 90% 11.3% [2] This means that together with the baseline case and the oxyfuel combustion case we introduce in this work the CLC coupled with NGCC, where main data are taken from the abovementioned study of Fan et al. 2018 [11], and also the H2-CC (this means a combined cycle powered by hydrogen). Dealing with CC powered by 100% hydrogen, this is an emerging technique which is thought to enter the market in the next years, an example is represented by the Vattenfall’s Magnum GTCC plant (440 MW) in the Netherlands which will be reconverted by MHPS from natural gas to hydrogen in 2025 [15]. Also Fusina power plant in Italy was fired with hydrogen from 2010 to 2018 (16 MW, efficiency estimated to be 43%, employing a GE10-1 type, single shaft, 11 compressor stages, 3 turbine stages) [16]. More than 75 GE gas turbines have operated on fuels containing hydrogen, accumulating more than 5 million operating hours. An example of hydrogen fleet leader can be considered a Frame 6B unit at the Daesan petrochemical plant in Korea, which was installed in 1997 and is routinely running with hydrogen concentrations between 85% and 97% [16]. Also the HYFLEXPOWER goes in this direction [17]. Table 3 shows the main models of gas turbines which have been tested till now. Not all the producers have reached 100% H2 combustion but they are approaching to it very fast. So it can be considered a feasible and soon marketable technology. The European Turbine Network (ETN) report on Hydrogen Gas Turbines [18]. From that report we can understand that there are turbines which can run on high concentrations of * (IEA, 2008). 5 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI hydrogen, as reported in table 3. An efficiency of 57.7% is supposed for the CC, according to Chiesa et al. 2005 [14]. Table 3. Gas Turbines models designed to run on H2 [18]. Company Turbines models % H2 Ansaldo GT36 H 0-50% GT26 F 0-45% E94.3A F-class 0-25% GE 6B/7E/9E* 0-35% E and F-class machines* 0-40% BH GE10-1 0-100% Aeroderivative, B/E Class, F-Class, HAClass 0-100% Nova-LT 0-100% GE Aeroderivative 85% B/E-class 100% F-class 65% HA Class 50% Mann THM 0-60% MHPS Multi-nozzle combustor 0-30% Multi-cluster combustor 0-80% Diffusion combustor 0-90% Siemens Aeroderivative 0-100% Utility gas turbines 0-30% SGT-600 to SGT-800 0-60% SGT-100 and SGT-300 0-30% SGT-400 0-10% Solar Turbines Titan 130 and Taurus 60 0-60% *retrofitted 2.3 Natural Gas Combined Heat and Power plants (NGCC plants) in the framework of the Italian National Energy Policy The latest Italian National Energy Strategy (SEN 2017) [19] aims at increasing the penetration of renewable energy in Italy. Part of the polices developed to support Energy Transition in Italy is also present in the Proposal of the National Integrated Plan for Energy and Climate [20]. Energy planning in Italy at a governmental level is based of the Italian Energy System simulations performed with the Times-Italia model developed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development [21]. While the Italian commitments on renewable energies are quite clearly expressed in the SEN it is very probable that the current NGCC plants, see figure 3 and figure 4, will remain strategic as well. Figure 3 presents the locations of the existing NG power plants in Italy, as derived from the Global Power Plants Database. In red we see the CC in blue the gas turbines and in green the IGCCs. Figure 4 presents the power plants capacities. We see that the average capacity is about 677 MW with a standard deviation of 549 MW, this means that the power capacity changes quite a lot. The maximum capacity is represented by the Montalto power station 6 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI hydrogen, as reported in table 3. An efficiency of 57.7% is supposed for the CC, according to Chiesa et al. 2005 [14]. Table 3. Gas Turbines models designed to run on H2 [18]. Company Turbines models % H2 Ansaldo GT36 H 0-50% GT26 F 0-45% E94.3A F-class 0-25% GE 6B/7E/9E* 0-35% E and F-class machines* 0-40% BH GE10-1 0-100% Aeroderivative, B/E Class, F-Class, HAClass 0-100% Nova-LT 0-100% GE Aeroderivative 85% B/E-class 100% F-class 65% HA Class 50% Mann THM 0-60% MHPS Multi-nozzle combustor 0-30% Multi-cluster combustor 0-80% Diffusion combustor 0-90% Siemens Aeroderivative 0-100% Utility gas turbines 0-30% SGT-600 to SGT-800 0-60% SGT-100 and SGT-300 0-30% SGT-400 0-10% Solar Turbines Titan 130 and Taurus 60 0-60% *retrofitted 2.3 Natural Gas Combined Heat and Power plants (NGCC plants) in the framework of the Italian National Energy Policy The latest Italian National Energy Strategy (SEN 2017) [19] aims at increasing the penetration of renewable energy in Italy. Part of the polices developed to support Energy Transition in Italy is also present in the Proposal of the National Integrated Plan for Energy and Climate [20]. Energy planning in Italy at a governmental level is based of the Italian Energy System simulations performed with the Times-Italia model developed by the Italian National Agency for New Technologies, Energy and Sustainable Economic Development [21]. While the Italian commitments on renewable energies are quite clearly expressed in the SEN it is very probable that the current NGCC plants, see figure 3 and figure 4, will remain strategic as well. Figure 3 presents the locations of the existing NG power plants in Italy, as derived from the Global Power Plants Database. In red we see the CC in blue the gas turbines and in green the IGCCs. Figure 4 presents the power plants capacities. We see that the average capacity is about 677 MW with a standard deviation of 549 MW, this means that the power capacity changes quite a lot. The maximum capacity is represented by the Montalto power station (also known as Alessandro Volta power station), which is a multifuel power plant mainly used as CC. Fig. 3. Italian NGGT plants according to the Global Power Plants Database, [6] Fig. 4. Italian NGGT power plants capacities [6]. We can reasonably assume that the existing NGCC plants will be used to cover the base load demand of electricity. The final energy mix referred to 2030 is presented in figure 4. 7 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI We can see that, according to the SEN, the total renewable electricity production will be about 184 TWh per year, while the electricity production from natural gas is assumed to be about 120 TWh (to make calculations easier in this case we have added the electricity produced from natural gas – which is equal to 118 TWh to the electricity produced from other oil derivates – which is equal to 2 TWh -). Fig. 5. Italian energy mix in 2030, according to SEN [19]. Fig. 6. Integration of EnergyPlan with LCA, methodology. 8 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI We can see that, according to the SEN, the total renewable electricity production will be about 184 TWh per year, while the electricity production from natural gas is assumed to be about 120 TWh (to make calculations easier in this case we have added the electricity produced from natural gas – which is equal to 118 TWh to the electricity produced from other oil derivates – which is equal to 2 TWh -). Fig. 5. Italian energy mix in 2030, according to SEN [19]. Fig. 6. Integration of EnergyPlan with LCA, methodology. To improve further the reduction of GHG emissions it can be interesting to gradually upgrade the NGCC plants to new and more clean technologies, as those presented in table 2: CLC combustors, oxy-fuel combustors and also H2 gas turbines are still in development we can compare the convenience of introducing these technologies to upgrade existing CC power plants in 2030. This is done with the methodology considered in figure 4. The different scenarios are implemented in the software EnergyPlan. finding the total investment costs of the system and also the total CO2 emissions. The above mentioned software has been developed by the university of Aalborg in Denmark [22] and it is used to model energy systems at a national, regional or local level to develop smart energy systems based on high renewable energy penetration. To build a model in the EnergyPlan software [22] a relevant part is the collection of the required data. For this aim in this study we have referred to the Italian energy model 2010 and the business-as-usual model 2050 [23]. These have been updated and calibrated to 2030 using the targets set in the SEN and reported in figure 5. 2.4 Attributional LCA analysis on the technologies to upgrade NGCC power plants LCA analysis is based on ISO 14040 and ISO 14044 norms. The Goal of the analysis is “to provide information on the impact (and more specifically on the carbon footprint) of cleaner technologies used to upgrade existing NGCC”. Where for cleaner technologies we intend those presented in table 2. For NGCC power plants attributional analysis the PCR developed in 2007 (version 4, valid until 2024) by the International EPD system (Environdec) [24]: “ELECTRICITY, STEAM AND HOT WATER GENERATION AND DISTRIBUTION PRODUCT CATEGORY CLASSIFICATION: UN CPC 171, 173” was adopted. Dealing with the Scope of the study, the following assumptions are made: - the functional unit is set to be: electricity production; - the reference flow is set to be 1 MWh; - the system boundaries are shown in Figure 7. Fig. 7. Coupled NGGT and CLC combustor. 9 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI - 367 MtCO2 can be reduced by upgrading NGCC to oxy-NGCC (reduction of 42%). Dealing with the total emissions amount shown for the business-as-usual case (which is the conventional NGCC) this is about 864 MTCO2. If we consider the Italian national inventory of GHG it reports that in 2016 the emissions due to the entire power sector were 335 MtCO2. So this means that if the emissions are calculated in the entire life cycle of the power plants these can be 2.6 higher. 4 Conclusions Economic and environmental analysis have been applied to the comparison of three possible technologies to be used to upgrade NGCC power plants in Italy. The first technology taken into account is Chemical Looping Combustion which by combusting the natural gas with oxygen carriers (instead of gaseous oxygen) produces a pure stream of CO2 which can be easily captured and compressed (this technology is currently at TRL 6). The second technology is direct combustion of 100% hydrogen in the gas turbine combustion chamber (this technology is approaching the market now). The third technology is oxyfuel combustion of natural gas in gas turbines and then CCS. Also this last technology is approaching the market and it has been already tested for coal but for natural gas it needs more R&D. The results show that all the considered technologies can have a high impact at relatively low investment cost. In fact the existing power facilities can be upgraded and don’t require to be build ex-novo. This is an interesting advantage. The reduction on the GHG emissions released during the total life cycle of the entire power sector in Italy could be halved. 5 Nomenclature Symbols in the manuscript should be included in a nomenclature list grouped into symbols, subscripts/superscripts, and acronyms/abbreviations with placement before the references. CLC Chemical Looping Combustion - CLC-NGCC Coupled CLC combustor and NGCC - H2-CC Hydrogen fed Combined Cycle - NG Natural Gas - NGCC Natural Gas Combined Cycle - Oxy-NGCC Oxy-fuel Combustion NGCC - P2G Power to Gas - SEN Italian National Energy Strategy - SMR Steam Methane Reforming - CG Coal Gasification - BMG Biomass Gasification - BDL-E-Corn Reforming of Ethanol from corn - BDL-E-Wheat Reforming of Ethanol from wheat - E-PEM Proton Exchange Membrane - E-PEM-R Electrolysis with Proton Exchange membrane with wind energy - E-SOEC Electrolysis with Solid oxide electrolysis cells - E-SOEC-R Electrolysis with Solid oxide electrolysis cells with wind energy - DF-MEC w/out R Dark fermentation + microbial electrolysis cell without energy recovery - 16 E3S Web of Conferences 312, 08019 (2021) https://doi.org/10.1051/e3sconf/202131208019 76° Italian National Congress ATI - 367 MtCO2 can be reduced by upgrading NGCC to oxy-NGCC (reduction of 42%). Dealing with the total emissions amount shown for the business-as-usual case (which is the conventional NGCC) this is about 864 MTCO2. If we consider the Italian national inventory of GHG it reports that in 2016 the emissions due to the entire power sector were 335 MtCO2. So this means that if the emissions are calculated in the entire life cycle of the power plants these can be 2.6 higher. 4 Conclusions Economic and environmental analysis have been applied to the comparison of three possible technologies to be used to upgrade NGCC power plants in Italy. The first technology taken into account is Chemical Looping Combustion which by combusting the natural gas with oxygen carriers (instead of gaseous oxygen) produces a pure stream of CO2 which can be easily captured and compressed (this technology is currently at TRL 6). The second technology is direct combustion of 100% hydrogen in the gas turbine combustion chamber (this technology is approaching the market now). The third technology is oxyfuel combustion of natural gas in gas turbines and then CCS. Also this last technology is approaching the market and it has been already tested for coal but for natural gas it needs more R&D. The results show that all the considered technologies can have a high impact at relatively low investment cost. In fact the existing power facilities can be upgraded and don’t require to be build ex-novo. This is an interesting advantage. The reduction on the GHG emissions released during the total life cycle of the entire power sector in Italy could be halved. 5 Nomenclature Symbols in the manuscript should be included in a nomenclature list grouped into symbols, subscripts/superscripts, and acronyms/abbreviations with placement before the references. CLC Chemical Looping Combustion - CLC-NGCC Coupled CLC combustor and NGCC - H2-CC Hydrogen fed Combined Cycle - NG Natural Gas - NGCC Natural Gas Combined Cycle - Oxy-NGCC Oxy-fuel Combustion NGCC - P2G Power to Gas - SEN Italian National Energy Strategy - SMR Steam Methane Reforming - CG Coal Gasification - BMG Biomass Gasification - BDL-E-Corn Reforming of Ethanol from corn - BDL-E-Wheat Reforming of Ethanol from wheat - E-PEM Proton Exchange Membrane - E-PEM-R Electrolysis with Proton Exchange membrane with wind energy - E-SOEC Electrolysis with Solid oxide electrolysis cells - E-SOEC-R Electrolysis with Solid oxide electrolysis cells with wind energy - DF-MEC w/out R Dark fermentation + microbial electrolysis cell without energy recovery - DF-MEC w/ER Dark fermentation + microbial electrolysis cell with energy recovery - DF-MEC w/H2 Recovery Dark fermentation + microbial electrolysis cell with H2 recovery - Acknowledgments This work has been partially funded by the GTCLC-NEG project that has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie SklodowskaCurie grant agreement No. 101018756. 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