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Refined bio-crude production from hydrothermal liquefaction of algae holds the potential to replace fossil-based conventional liquid fuels. The microalgae act as natural carbon sequestrators by consuming CO₂. However, this absorbed CO₂ is released to the atmosphere during the combustion of the bio-crude. Thus, the life-cycle greenhouse gas (GHG) emissions of refined bio-crude are linked to the production and supply of the materials involved and the process energy demands. One prominent raw material is CO₂, which is the main source of carbon for algae and the subsequent products. The emissions associated with the supply of CO₂ can have a considerable impact on the sustainability of the algae-based refined bio-crude production process. Furthermore, the diurnal algae growth cycle complicates the CO₂ supply scenarios. Traditionally, studies have relied on CO₂ supplied from existing power plants. However, there is potential for building natural gas or biomass-based power plants with the primary aim of supplying CO₂ to the biorefinery. Alternately, a direct air capture (DAC) process can extract CO₂ directly from the air. The life-cycle GHG emissions associated with the production of refined bio-crude through hydrothermal liquefaction of algae are presented in this study. Different CO₂ supply scenarios, including existing fossil fuel power plants and purpose-built CO₂ sources, are compared. The integration of the CO₂ sources with the algal biorefinery is also presented. The CO₂ supply from biomass-based power plants has the highest potential for GHG reduction, with a GHG footprint of −57 g CO₂ eq./MJ refined bio-crude. The CO₂ supply from the DAC process has a GHG footprint of 49 CO₂ eq./MJ refined bio-crude, which is very similar to the scenario that considers the supply of CO₂ from an existing conventional natural gas-based plant and takes credit for the carbon utilization.