Biofuels and CO2 neutrality: an opportunity

CO2- neutral bioprocesses are of immanent concern and can be coupled by using integrated bioprocess and biofuel production systems. Existing biofuel generations are, therefore, reclassified according to the current possible bioprocessing routes. Only the first biofuel generation has been successfully carried into a commercial scale, while the second is still being improved at laboratory scale or in pilot-scale processes. Biodiesel and biohydrogen, as third-and fourth-generation biofuels, respectively, are also being studied at the laboratory scale. Here, we introduce the fifth biofuel generation, which is based on biological CH4 production from gaseous raw materials. The integration of bioprocess systems and the coupling between different biofuel generations under CO2 neutrality is analyzed and presented to be of great interest for industry and science. Value-added production (i.e., recombinant proteins) can be coupled to CO2- neutral integrated biofuel production systems and, hence, integration of different biofuel generations within a biorefinery concept could be translated into a reality.