Zero discharge tanning: a shift from chemical to biocatalytic leather processing

Area of Science:

• Green Chemistry
• Biotechnology
• Materials Science

Background:

• Beam house processes in leather production are major pollution sources, primarily due to lime and sodium sulfide use.
• Conventional liming-re-liming processes generate significant lime sludge and total solids, posing environmental challenges.
• Lime is crucial for osmotic swelling and fiber opening in traditional leather processing.

Purpose of the Study:

• To develop an alternative bioprocess eliminating lime from leather beam house operations.
• To assess the efficacy of enzymatic dehairing and alpha-amylase for fiber opening.
• To evaluate the environmental impact and leather quality of the novel lime-free process.

Main Methods:

• Enzymatic dehairing using a low concentration of sodium sulfide.
• Fiber opening utilizing alpha-amylase post-enzymatic dehairing.
• Comparative analysis with conventional liming-re-liming processes using SEM, chrome distribution, and softness measurements.

Main Results:

• The alpha-amylase process achieved comparable fiber bundle opening to conventional liming.
• Leather quality, including softness, was on par with conventionally produced leather.
• Significant reductions in pollution load: 45% decrease in Chemical Oxygen Demand and 20% in total solids.
• Drastic reduction in dry sludge from 152 kg to 8 kg per ton of raw hides.

Conclusions:

• A lime-free bioprocess for leather beam house operations is feasible and effective.
• Enzymatic dehairing combined with alpha-amylase offers a sustainable alternative to traditional methods.
• The new process substantially reduces environmental impact without compromising leather quality.