Scale-up of rhamnolipid biosynthesis via agro-waste valorization: Techno-economic assessment with cradle-to-gate life cycle analysis

Abstract

This work explores a waste valorization approach for producing rhamnolipids using two abundant residues: crude cellulose (40%) derived from sawdust and crude glycerol (45%) from waste cooking oil. Rigorous experimental studies showed that mono-substrate fermentations resulted in lower product yields, prompting the use of dual-substrate (3% w/v cellulose + 3% w/v glycerol) fermentations by Pseudomonas aeruginosa 2297. Dual-substrate fermentations produced the highest titer of 6021 ± 235.25 mg/L of rhamnolipids, compared to the respective product concentrations of 3711.37 ± 34.3 mg/L and 1634.90 ± 131.49 mg/L obtained with crude glycerol (4% w/v) and crude cellulose (4% w/v) as sole carbon sources, respectively. Produced rhamnolipid showed about 40.73 ± 2.09% oil recovery using a sand-packed column. Techno-economic evaluation established a minimum selling price of USD 1.57/g at a null net present value, indicating potential economic competitiveness. A cradle-to-gate life cycle assessment showed a carbon footprint of 1.73 kg CO2-eq/g of rhamnolipid, which is better than that reported in recent literature. Further optimization of utility consumption parameters can reduce the carbon footprint and other environmental impacts, thereby providing a basis for appropriate policy recommendations.