## 3 Results and Findings from the Existing Literature  
This review encapsulates findings from 34 case studies featured in 23 articles, extensively examining the TEAs and LCAs of e-fuel production involving H2 and atmospheric CO2. The distribution of these studies is visually represented in Figure 5, showcasing a pie chart based on continents. Notably, a substantial majority of the investigations concentrate on European countries, constituting a significant 59% of the total cases, which amounts to 20 out of the 34 studies. Following this, North America emerges with an 11% share, while both Asian and South American studies each contribute 9%. Africa and Australia round out the distribution with equal shares of 6%. This continental breakdown underscores the regional focus of current research efforts, emphasising Europe's prominent role in advancing the understanding of e-fuel production dynamics.  
Figure 6 provides a detailed breakdown of selected countries contributing to the research landscape. The distribution is as follows: Germany (6/34), Italy (5/34), Sweden (2/34), and 1 each from Denmark, Netherlands, the UK, Turkey, Norway, Iceland, and others within the EU. For the North American continent (7/34), contributions come from the USA (3/7), Chile (2/7), and 1 each from Canada and Argentina. In Asia, with 3/34, the country-wise distribution of studies is equally distributed from China, Saudi Arabia, and the UAE. Examining economic comparisons of e-fuels in Africa (2/34), one each was found from Namibia and Egypt. Australia with two such studies is comparatively modest.  
Figure 5: Continental distributions of TEA and LCA studies on e-fuel.  
The primary energy sources in Europe are dominated by local renewables, with photovoltaic accounting for 25% (5/20) and wind contributing 15% (3/20). Furthermore, a significant portion, 40% (8/20), is derived from a combination of solar, PV, and hydro. Geothermal and nuclear sources collectively contribute 10% (2/20), while fossil and biomass sources make up 5% (1/20), along with 5% (1/20) from unspecified sources. In Asia, primary energy sources encompass a blend of local renewables and fossil fuels, with photovoltaic accounting for two out of three cases. Additionally, a single case involves a mix of natural gas, crude oil, and coal. Africa, while making a modest contribution, relies on solar and PV sources (2/2). Refer to Figure 6 for a visual representation of these distributions, and for a concise overview of previous research findings on the techno-economic analysis of e-fuel production, please consult Table 1. In North America (7/34), which includes North America (4/7) and South America (3/7), primary energy sources are diversified, combining fossil, nuclear, solar, and wind electricity [49].  
Australia holds a prominent position as one of the world's major exporters of renewable energy. The country's primary energy sources draw from a combination of factors, notably high wind speeds and abundant solar radiation, constituting two out of two cases. Australia's role as a significant energy exporter plays a pivotal role in the global energy landscape. Notably, hydrogen production solely from solar panels covering 3% of Australia's land area has the potential to offset 10 times Germany's non-electricity energy consumption. As hydrogen technologies continue to advance and achieve higher technological readiness levels, costs are consistently decreasing across all levels. However, the cost of storage and transportation distances remains a crucial consideration for Australia's renewable energy export. Given that the global move towards defossilisation is a collective challenge, further studies are imperative, emphasising the need for global cooperation [50].  
Figure 6: Distributions of TEA and LCA studies on e-fuel.