Biomass-based curing agents for sustainable leather processing

The biomass utilization without purification and fractionation through a non-selective manner is the best option for high conversion efficiency. Leftover and abundant plant biomass can be a source of preservatives if they keep antimicrobial activity against spoilage microorganisms. Traditionally, 50% w/w sodium chloride (NaCl) is employed for hides and skin preservation (curing). However, enormous water pollution, aquatic toxicity, soil infertility, and high chemical consumption make it questionable. This study investigates biomass-based curing (BBC) agents from Cynodon dactylon grass and Alzibia lebbeck leaves. The plant’s dry powder was directly applied over goatskin and evaluated curing efficiencies. The BBC formulations were user-friendly, highly biomass conversion efficiency (41-53% of raw wt.) and antimicrobial activity (against E. coli: 17-18 mm and B. subtilis: 15-17 mm), and preserved goatskin for 30 days like NaCl. It reduced the salinity and total dissolved solids (TDS) load from tannery-soaking effluent by 67-74% and 41-65%, respectively. The environmental efficiency index (EEI) revealed that BBC systems (EEI: 29.9-31.3) are around 1.5 times more environmentally sustainable than conventional curing (EEI: 20.7). Besides, the alternatives have no effect on the features of final leather. In conclusion, the ecofriendly BBC agents have the potential to minimize the heavy pollution of salt curing.