## 3 Results and Findings from the Existing Literature
### Techno-Economic Analysis (TEA)
They performed sensitivity analyses and process evaluations. Results from both indirect and direct processes indicated production rates of 66.18 bbl/d and 38.46 bbl/d, respectively. Additionally, the product cost varied significantly, ranging from 460-1435 USD/bbl for the indirect process to 752-2364 USD/bbl for the direct process. The study pinpointed a strong dependency on power energy and hydrogen prices. In 2021, Sweden also delved into a techno-economic assessment projected for the 2020-2050 timeline. Using the Fischer-Tropsch (FT), HTL, and PTL (with a Python 3.9 MILP model) methods, they focused on producing RJF from lignocellulosic biomass and captured CO\({}_{2}\)[62]. The study projected an increase in total RJF production, attributed to the blending ratio. By 2030-2050, they anticipate RJF production to be in the range of 3.85-16.87 TJ. Moreover, the HTL and PTL jet fuel production costs vary, with prices anticipated between 24.2-25.4 SEK/litre or 5-5.5 USD/litre and 16.7-22.0 SEK/litre or 3.5-4.5 USD/litre, respectively. Significantly, revenue generated from by-products could potentially make HTL and PTL methodologies price-competitive. A techno-economic assessment (TEA) by [PERSON], [PERSON] [63] revealed critical challenges related to the cost and market potential of e-fuels. Notably, OME3-5 e-fuels exhibit significantly higher cost of goods manufactured per gigajoule (GJ) compared to conventional diesel fuel available at gas stations in Germany. Additionally, the study indicated that less than 38.4% of electricity can be efficiently stored in e-fuel, based on lower heating value. The most substantial economic barriers identified in the analysis are associated with electricity consumption and the cost of electrolyser stacks rather than the OME conversion cost. Even with a significant reduction in electricity or electrolyser prices, the OME3-5 anhydrous pathway would not be economically competitive under current conditions. This emphasises the need for significant advancements in reaction processes and system improvements to enhance the economic viability of OME3-5 e-fuels in the future. In 2019, [PERSON], [PERSON] [64] provided valuable insights into the costs and life cycle of greenhouse gas (GHG) emissions associated with the production of electrolytic hydrogen and subsequent conversion to ammonia (e-ammonia). The study highlights the critical role of electricity sources in determining the environmental footprint of e-ammonia production. Notably, the research underscores the influence of the grid's electricity sources, with North Chile using a substantial 58% of grid electricity and emitting 183 gCO\({}_{2}\)/MJNH\({}_{3}\), whereas Denmark, with a higher share of green electricity, emits only 109 gCO\({}_{2}\)/MJNH\({}_{3}\) using 100% grid electricity to optimise the sustainability of e-ammonia production. [PERSON], [PERSON] [65] highlight a critical concern regarding the storage of CO\({}_{2}\) resulting from IPCC scenarios. The study emphasises that the significant volume of CO\({}_{2}\) requiring storage could potentially create a shortage of suitable, cost-effective, and readily available CO\({}_{2}\) storage sites. In this context, the analysis draws attention to the cost difference between e-fuels and direct air capture and carbon storage (DACCS) options, indicating that this difference ranges between 1.0% and 2.5% of the ticket price by 2050. Importantly, the study suggests that this cost variation is a reasonable burden for passengers to bear. Therefore, it encourages the consideration of the e-fuels option as a more consistent choice with the precautionary principle, which is a fundamental principle in environmental policy. The precautionary principle underscores the need to prioriti actions that prevent potential harm to the environment and human well-being.