(118b) Assessing Sustainable Aviation Fuels (SAF) Pathways through the Retrofitting of Gtl Processes: A Step Towards the Integration of Renewable Energy and Ccu Techniques.

The aviation industry is one of the major contributors to global greenhouse gas (GHG) emissions, which has raised concerns about environmental sustainability and climate change. In fact, it is responsible for over 2% of global CO₂ emissions and contributes to 3.5% of climate change. Due to the mounting pressure to address the environmental impact of the aviation industry, Sustainable Aviation Fuel (SAF) has emerged as a promising solution to neutralize emissions. SAF is derived through two main pathways: Biofuel SAF and Synthetic SAF. Biofuel SAF is made from renewable resources such as energy crops, fat oils, agricultural residues, etc. On the other hand, synthetic SAF is produced using conventional technologies like XTL (where X stands for gas, liquid, or solid, such as natural gas, crude oil, coal, and municipal solid waste). GTL aviation fuel has a carbon intensity value of 100 g CO₂e/MJ, while conventional jet fuel made from crude oil has a slightly lower value of 84 g CO₂e/MJ. However, there are alternative sources, like Synthetic Paraffinic Kerosene (SPK), made from bio SAF, that produce a range of 6 g CO₂e/MJ to 49 g CO₂e/MJ [1], depending on the source and production process. Despite this, most aviation fuel is still produced using synthetic methods, so finding ways to decarbonize these processes is critical. To address this challenge, the present work explores decarbonization solutions by implementing a hybrid Carbon Capture Utilization (CCU) and renewable energy approach in conventional GTL processing facilities.

Our methodology involves the establishment of a reference scenario where a conventional GTL plant is designed for SAF production. Subsequently, we implement a series of modifications: First, we transition the plant's energy source from natural gas to solar energy, reducing its carbon footprint by 65% and fossil fuel reliance. Secondly, we integrate an innovative reforming technology known as CARGEN®, which was previously developed in our research group. This technology enables the recycling of direct CO₂ emissions that is normally flared in conventional plants by reaction with natural gas to produce carbon-neutral or even carbon-negative products; multi-walled carbon nanotubes (MWCNTs) and syngas. Ultimately, we retrofit the reforming process within the GTL plant with renewable methods, including electrolysis and the utilization of the water gas shift reaction for comparison with the developed hybrid approach in the first two processes. After careful analysis and assessment, these changes were compared to the predefined SAF production CO₂ emissions targets in the range of 6 g CO₂e/MJ to 49 g CO₂e/MJ.

Based on our preliminary targeting assessments, we have identified the potential to significantly reduce the carbon intensity of the existing GTL process. Our assessments have shown that we can lower the carbon intensity from 136 g CO₂e/MJ to 13 g CO₂e/MJ by the implementation of solar energy in place of natural gas via an electrification approach. By comparing CCU technologies such as CARGEN®, water electrolysis, or water gas shift reaction; the best options for CO₂ sequestration for achieving net-zero or even carbon-negative emissions are being identified. The comparison is underway to establish both sustainability and economic outlooks of the aforementioned CCU technologies. This research is part of a decarbonization initiative for the process industry, utilizing innovative carbon capture and renewable energy solutions. The presentation will highlight the recent developments within the project, offering insights into sustainability objectives, capital investments, and the economic advantages derived from the strategic transformation of the GTL sector to produce SAF.

References:

[1] R. G. Grim et al., “Electrifying the production of sustainable aviation fuel: the risks, economics, and environmental benefits of emerging pathways including CO2,” Energy Environ Sci, vol. 15, no. 11, pp. 4798–4812, Oct. 2022, doi: 10.1039/d2ee02439j.

[2] Z. Ataya, M. Challiwala, G. Ibrahim, H. A. Choudhury, M. M. El-Halwagi, and N. O. Elbashir, “Decarbonizing the Gas-to-Liquid (GTL) Process Using an Advanced 2 Reforming of Methane Process”, doi: 10.1021/acsengineeringau.3c00025.