Cross‐sectoral citrus sugarcane biorefinery: polyhydroxyalkanoates production in Brazil

Abstract

Polyhydroxyalkanoates (PHA) are naturally occurring polyesters accumulated by bacteria under conditions of inorganic nutrient limitations and excess carbon. They offer renewable and biodegradable alternatives to petroleum‐based polymers, especially those used in transient single‐use applications. However, PHA still faces high production costs, primarily linked to the carbon source, lower productivity in processes and an early stage of technical development in comparison with well‐established fossil‐based polymers, which challenge its transition to a true commodity market. Recent research has highlighted the potential of renewable, inexpensive, abundant and non‐edible carbon‐rich residues from agriculture, municipal solid waste and industrial byproducts as alternative carbon sources in developing the production process. Recognizing Brazil's position as the leading producer of both citrus and sugarcane, this review introduces a novel citrus–sugarcane biorefinery model for PHA production, capitalizing on the geographical and operational synergies of both sectors. The proposed model integrates wet citrus pulp as a second‐generation carbon source, sugarcane industry fermenters, waste management, solvents and renewable energy from both sectors. Primary challenges involve the need for efficient, low‐cost biomass pre‐treatment to remove limonene and partially extract citric pectin, coupled with the partial hydrolysis of pectin to enhance solubility and reduce viscosity. Additional considerations include determining citrus biomass composition and sugar consumption, screening bacterial diversity for optimal PHA production, and deepening our understanding of the metabolic pathways underpinning the catabolism of citrus residues. Future research should focus on enhancing PHA concentrations and diversity and finally conducting life cycle assessment studies to evaluate the sustainability and feasibility of this proposed model.