Nixon Sunny
Senior Research Scientist
Saudi Aramco
Dr. Nixon Sunny is a Senior Research Scientist at Saudi Aramco’s Technology Strategy & Planning Department. With a PhD from Imperial College London, he has authored influential works on low-carbon energy systems — including hydrogen and CCS infrastructure, ammonia, and pathways to decarbonise power, heat, industry, and carbon dioxide removal. Through his research and collaborations, Dr. Sunny bridges academia, industry, and policy to help deliver insights for in-house technology development and business investment.
Participates in
TECHNICAL PROGRAMME | Primary Energy Supply
Natural Gas as a Transition Fuel
Forum 04 | Technical Programme Hall 1
29
April
10:00
11:30
UTC+3
Natural gas is expected to play a major role in Saudi Arabia’s energy system as the Kingdom advances toward Vision 2030 and its net-zero target by 2060. The Saudi Green Initiative (SGI) aims to achieve a share of 50% renewable energy and 50% natural gas in the Kingdom’s power generation capacity. This will increase the domestic consumption of natural gas, while leveraging its lower carbon intensity (CI) for power generation (350 - 450 kgCO2,eq/MWh) compared to oil-fired generation (600 - 800 kgCO2,eq/MWh). Overall, the SGI target can significantly reduce the CI of the electricity grid in Kingdom to approximately 200 kgCO2,eq/MWh. In this context, this study evaluates the potential to further reduce GHG emissions from natural gas-fired combined cycle gas turbines (CCGTs) through the integration of carbon capture and storage (CCS).
Here, the cost of CO2 avoidance is evaluated for natural gas CCGTs and CCGTs with CCS using techno-economic modelling and life cycle assessments for the Kingdom of Saudi Arabia (KSA), using its power grid as the reference case. The analysis suggests that investments in CCGTs (without CCS) incurs a cost of CO2 avoidance of $ 6/ton – $ 25/ton, until a total grid CI of approximately 400 kgCO2,eq/MWh is reached. Following which, investments in CCGT in Kingdom will accrue an exponentially increasing marginal cost of CO2 avoidance as CCGT plants do not offer any further GHG reduction potential for the grid, yet still incurs capital and operating costs. At this point, investments in CCGTs with CCS are likely to look more attractive. The cost of CO2 avoidance for natural gas CCGTs with CCS is in the range of $ 20/ton – $ 100/ton, until a total grid CI of less than 75 kgCO2,eq/MWh is reached.
Two key considerations are important to ensure a lower CI from natural gas CCGTs with CCS – lower upstream methane emissions, and higher average CO₂ capture rates. When natural gas with lower upstream emissions (≤ 5 kg CO₂,eq/GJ) is used in conjunction with an average capture rate of 95+%, CCGTs with CCS can achieve carbon intensities as low as 75 kg CO₂eq/MWh. This CI is equivalent to a system which is comprised of 80% renewables and 20% natural gas CCGTs, which may take decades to develop and mature. KSA benefits from domestic gas production with relatively lower upstream emissions which can help accelerate emissions reductions.
Nonetheless, even the best-performing CCGT plants retrofitted with CCS will generate residual emissions. Addressing these will require durable carbon dioxide removal solutions, such as direct air capture and storage, or waste-to-energy plants with CCS, which can be deployed within KSA by utilizing its extensive geological storage potential.
Here, the cost of CO2 avoidance is evaluated for natural gas CCGTs and CCGTs with CCS using techno-economic modelling and life cycle assessments for the Kingdom of Saudi Arabia (KSA), using its power grid as the reference case. The analysis suggests that investments in CCGTs (without CCS) incurs a cost of CO2 avoidance of $ 6/ton – $ 25/ton, until a total grid CI of approximately 400 kgCO2,eq/MWh is reached. Following which, investments in CCGT in Kingdom will accrue an exponentially increasing marginal cost of CO2 avoidance as CCGT plants do not offer any further GHG reduction potential for the grid, yet still incurs capital and operating costs. At this point, investments in CCGTs with CCS are likely to look more attractive. The cost of CO2 avoidance for natural gas CCGTs with CCS is in the range of $ 20/ton – $ 100/ton, until a total grid CI of less than 75 kgCO2,eq/MWh is reached.
Two key considerations are important to ensure a lower CI from natural gas CCGTs with CCS – lower upstream methane emissions, and higher average CO₂ capture rates. When natural gas with lower upstream emissions (≤ 5 kg CO₂,eq/GJ) is used in conjunction with an average capture rate of 95+%, CCGTs with CCS can achieve carbon intensities as low as 75 kg CO₂eq/MWh. This CI is equivalent to a system which is comprised of 80% renewables and 20% natural gas CCGTs, which may take decades to develop and mature. KSA benefits from domestic gas production with relatively lower upstream emissions which can help accelerate emissions reductions.
Nonetheless, even the best-performing CCGT plants retrofitted with CCS will generate residual emissions. Addressing these will require durable carbon dioxide removal solutions, such as direct air capture and storage, or waste-to-energy plants with CCS, which can be deployed within KSA by utilizing its extensive geological storage potential.
TECHNICAL PROGRAMME | Energy Infrastructure
CCS Hub Facilities
Forum 09 | Digital Poster Plaza 2
29
April
11:30
13:30
UTC+3
The Kingdom of Saudi Arabia (KSA) generates an estimated 18 – 30 million tons of municipal solid waste (MSW) annually, and this is expected to increase in the upcoming years with population growth. Currently, most of this waste is disposed in landfills, leading to land use pressures, and methane emissions. There is a national target to divert 94% of MSW from landfill by 2035, through recycling, waste-to-energy (WtE), composting, and other means. WtE incinerators reduce landfill waste volumes, lower greenhouse gas (GHG) emissions, and recover useful energy in the form of electricity. However, there is a gap in the literature on the capacity for WtEs with carbon capture and storage (CCS) to offer carbon-neutral power and negative emissions in KSA. This study addresses this gap and provides a comparative assessment of the techno-economic and life cycle performance of WtE power plants, integrated with and without CCS, to identify their value to the system.
Thermodynamic process models were developed to design two separate MSW WtE plant configurations – with and without CCS. The model takes inputs such as the MSW throughput, feed composition, steam cycle parameters, and CCS system parameters to calculate the net power output, lifecycle GHG emissions, and total system costs. A nominal design throughput of 25 t/h of MSW is used to evaluate the key performance indicators for both of the aforementioned cases. At plant level, a WtE generator without CCS produces nearly 19 MW, reflecting an overall cycle efficiency of 25%. When coupled with CCS using a 90% capture rate, this reduces to 12 MW, owing to the energy penalties associated with solvent regeneration and CO2 compression.
Diverting all the MSW generation in KSA (18 Mt/yr – lower estimate) to WtE plants produces approximately 13 TWh/year of power, helping to diversify the generation mix. However, the combustion of fossil-derived plastics and other wastes in MSW results in a carbon intensity of approximately 325 kg CO2,eq/MWh of power. When integrated with CCS, the WtE plants can produce approximately 9 TWh/yr of zero-carbon electricity, and 8.5 Mt CO2/yr of negative emissions in the KSA.
From a whole-systems perspective, both WtE systems achieve more than 90% reductions in landfill volume, significantly extending their lifetimes, and mitigating uncontrolled methane release. The marginal cost of carbon abatement for WtE with CCS, defined as the sum total of marginal cost of CO2 avoidance, and removal, is lower ($200 – $450/ ton) than that for direct air capture and storage ($400 – 1000/ ton), thus increasing the potential for commercial deployment. These findings are sensitive to the plant design and operation, as well as the feed compositions, but it highlights WtE with CCS as a unique contributor to the Kingdom’s energy system and circular carbon economy.
Thermodynamic process models were developed to design two separate MSW WtE plant configurations – with and without CCS. The model takes inputs such as the MSW throughput, feed composition, steam cycle parameters, and CCS system parameters to calculate the net power output, lifecycle GHG emissions, and total system costs. A nominal design throughput of 25 t/h of MSW is used to evaluate the key performance indicators for both of the aforementioned cases. At plant level, a WtE generator without CCS produces nearly 19 MW, reflecting an overall cycle efficiency of 25%. When coupled with CCS using a 90% capture rate, this reduces to 12 MW, owing to the energy penalties associated with solvent regeneration and CO2 compression.
Diverting all the MSW generation in KSA (18 Mt/yr – lower estimate) to WtE plants produces approximately 13 TWh/year of power, helping to diversify the generation mix. However, the combustion of fossil-derived plastics and other wastes in MSW results in a carbon intensity of approximately 325 kg CO2,eq/MWh of power. When integrated with CCS, the WtE plants can produce approximately 9 TWh/yr of zero-carbon electricity, and 8.5 Mt CO2/yr of negative emissions in the KSA.
From a whole-systems perspective, both WtE systems achieve more than 90% reductions in landfill volume, significantly extending their lifetimes, and mitigating uncontrolled methane release. The marginal cost of carbon abatement for WtE with CCS, defined as the sum total of marginal cost of CO2 avoidance, and removal, is lower ($200 – $450/ ton) than that for direct air capture and storage ($400 – 1000/ ton), thus increasing the potential for commercial deployment. These findings are sensitive to the plant design and operation, as well as the feed compositions, but it highlights WtE with CCS as a unique contributor to the Kingdom’s energy system and circular carbon economy.
