Sustainable production of bioplastic using Halomonas sp.: Enhancing process sustainability by minimizing waste generation

Abstract

Biopolymers, such as poly(3-hydroxybutyrate), offer a promising alternative to fossil-derived plastics. Although considerable attention has been paid to bacterial biopolymer production, the management of residual biomass after biopolymer extraction has received limited focus. This study aimed to promote a circular approach to sustainable poly(3-hydroxybutyrate) manufacturing by valorizing residual bacterial biomass, thereby contributing to sustainable biopolymer production. Halomonas sp. (strain halo6) produced poly(3-hydroxybutyrate) at 52 wt% under cultivation conditions with 1 % NaCl. The residual biomass, representing 48 wt% of the bacterial culture, was pyrolyzed to generate syngas. Syngas yields from pyrolysis under N2 and CO2 conditions showed no significant differences, despite the potential of CO2 to facilitate volatile thermal cracking. To improve the effectiveness of CO2 during pyrolysis, a catalyzed bed was introduced. Under CO2 conditions, the catalyzed pyrolysis setup produced 148.5 mmol of syngas, a 2.6-fold increase compared to N2conditions. With CO2-catalyzed pyrolysis, 80 wt% of the residual biomass was converted to syngas, while the remaining fraction was distributed between oil and char. Valorizing residual bacterial biomass from poly(3-hydroxybutyrate) production via CO2-catalyzed pyrolysis enhances the sustainability of the biopolymer production process, contributing to the circular bioeconomy and waste-to-energy conversion.