The aviation industry’s pursuit of achieving net zero hinges on large-scale and economical production of Sustainable Aviation Fuel (SAF). This study provides a comparative evaluation of the sustainability implications of SAF production pathways, particularly focusing on the integration of renewable energy sources and the potential for carbon emissions reduction. We investigated a three-step Alcohol-to-Jet pathway that integrates a thermochemical process to produce syngas (a mixture of CO and H2) from CO2 and a biological process to ferment syngas to ethanol, which is then converted to SAF via Alcohol-to-Jet. When compared with the industrially well-known Fischer-Tropsch process, the three-step Alcohol-to-Jet pathway demonstrates 1.6 times higher SAF yield and over 7% higher energy efficiency. Although the three-step Alcohol-to-Jet pathway has higher capital cost due to syngas fermentation, it produces SAF with the levelized cost of supply 14%-25% lower compared to Fischer-Tropsch pathway. Carbon intensity analysis shows that, to achieve comparable emissions as conventional jet fuel, at least 84.6% of the power used in SAF production must come from renewable sources. When renewable power is limited, utilizing methane as a feedstock can reduce overall emissions of SAF. Additionally, our findings on SAF economics highlight the necessity of policy interventions and incentives to advance SAF and renewable energy in the aviation sector.