Gas fermentation is gaining momentum. More and more bioprocesses rely on this technology, and PHA production makes no exemption. Indeed, several PHA producer start-ups and firms are testing the conversion of gases into polymers. However, C1 biological fixation faces a paradox: while gases like CO2 and CH4 are extremely abundant and polluting, thereby representing ideal feedstocks, their mass transportation within bioreactors and biomass is highly challenging.