Life cycle assessment of nature-based coagulant production: Light and dark sides of the freeze-drying process

Different review articles published in the last several years highlighted an importance and benefits of biocoagulants/bioflocculants utilisation in water and wastewater treatment as an eco-friendly and non-toxic alternative to currently used commercial ones. Although there is many research on various types of biocoagulants/bioflocculants (animal-, microorganism- and plant-based ones), there is still a significant knowledge gap which limits their utilisation at large scale. In order to achieve optimised solution several production options should be evaluated and compared in terms of their simplicity, economic viability, ecological impacts and their efficiency. When compared, these characteristics could lead to easier decision making and developing biocoagulant/bioflocculants with optimal eco-design. In order to compare 4 coagulant production processes for novel biocoagulant production (from common bean seed – Phaseolus vulgaris), life cycle assessment, cost analysis and performance within wastewater treatment were conducted in this study, while simplicity of each design is indicated as well. 4 distinct powdered coagulants were denoted as: KNO (conventional solid/liquid extraction with NaCl solution, spray dried), UNO (ultrasound extraction with NaCl solution, spray dried), GA (ultrasound extraction with NaCl solution, spray dried with gum Arabic as a carrier) and UVO (ultrasound extraction with distilled water, freeze dried). Based on the defined functional unit, KNO coagulant was the most eco-friendly and cost-beneficial coagulant, while UVO coagulant showed the highest coagulation ability. However, UVO coagulant has the most challenges within environmental deterioration, due to high electricity demand for freeze drying process. Although spray drying process showed ecological and economic benefits, high quality of freeze drying process should not be neglected and optimisation and comparison at full scale might be subject of future study. The present study also indicated at which points production process could be optimised by scale-up.