For the synthesis of hydrocarbons, a carbon source or, for power-based fuels, a carbon dioxide (CO₂) source is necessary alongside hydrogen. This CO₂ can either be captured from locally occurring streams with an elevated CO₂ concentration (so-called point sources) or from the air. Therefore, the following two possibilities will be distinguished:

• Carbon capture from point sources
• Direct air capture (DAC)
  
  

In principle, the effort required to provide CO₂ decreases as the concentration in the CO₂ source increases. Capturing from the air (0.042% by volume CO₂) is thus associated with significantly higher energy expenditure (and, due to the large air volumes, also structural effort) compared to capturing from point sources (10-50% by volume CO₂).