Alternative sources of carbon for moving towards a sustainable carbon cycle

Abstract

This perspective identifies the carbon needs of the chemical and transport industries in the short-to-medium term, categorizes the available renewable alternative carbon sources (biomass, waste-plastics and CO₂) to fossil carbon and discusses their usability and potential for the short-, medium- and long-term use. Given the constraints to the use of biomass (grown on purpose and waste) and the limited overall amount of waste plastics, CO₂ is the most abundant and at-hand source of renewable carbon. The conversion of CO₂ into chemicals, materials and energy products is discussed for meeting the energetic and hydrogen demands. The use of solar energy as a primary energy source and water as a proton and electron source in recycling carbon via CO₂ conversion into energy products is also elucidated. E-fuels and solar-fuels are compared for their commercialization, and the benefits of co-processing CO₂ and water (in electrochemical, photochemical and photoelectrochemical processes) instead of producing green-H₂ for CO₂ reduction are emphasized.

Keywords: Carbon dioxide as source of renewable carbon; Carbon cyclic economy; Photochemistry; Photoelectrochemistry; E-fuels; Solar-fuels