GREEN LIFE: GREEN Leather Industry For the Environment

PROJECT DESCRIPTION

BACKGROUND

The leather tanning process produces waste by-products equivalent to 50% of the raw material by weight. Around half of this material is used to produce fertilisers and biostimulants. However, a considerable part is not re-used or recycled. Tannery waste disposal does not make it possible to enhance the significant contribution to plant growth that the by-products of the tanning process can provide thanks to the high protein content and nitrogen in a bioavailable form, along with other substances. Leather tanning processes also generate volatile, particulate emissions into the atmosphere.

In addition, tanning wastewater presents significant management challenges. Around 1.91 kg of chemical products are used to treat one square metre of animal hide. In Italy alone, which accounts for 62% of EU leather production, this equates to 47 000 kg of chemical products per year. Around 31% of this volume is hazardous, according to the European Dangerous Substances Directive.

Tanning wastewater must therefore be suitably treated and controlled for suspended solids, COD, total nitrogen, ammonia, chromates, sulphides, chlorides and sulphates. Most of the sludge resulting from tannery wastewater purification treatment is considered hazardous and is sent to landfill.

OBJECTIVES

The GREEN LIFE project aimed to develop new technologies to reduce the environmental impact of the leather processing industry. It specifically planned to introduce an enzymatic and oxidative liming process to produce leather of the same quality as traditionally treated leather but with a lower environmental impact.

An enzymatic and oxidative liming process avoids the use of harmful and toxic substances such as sulphides and soluble chromium in the tanning treatment process. Such avoidance also reduces the volume of harmful waste by-products such as solid waste containing chromium and sulphates emerging from the process. The aim was also to reduce thevolume of unwanted hazardous atmospheric emissions.

The system would lead to the recovery of at least 20% of the used water volume for recycling back into the liming process. This would reduce water consumption as well as reducing the volume of wastewater. The demand on wastewater treatment facilities would be further reduced due to the reduced contamination of the water.

The project aimed to improve the selective recovery of by-products with industrial or agro-industrial value. Although it would not enable the valorisation of this waste stream, the aim is to reduce the quantity of solid waste sent to landfill or for additional treatment.

RESULTS

The GREEN LIFE project tested four innovative processes related to liming and tanning: liming with recovered bath and hair; oxidative liming; enzymatic liming and tanning; and using part of the resulting waste for agronomic purposes. The environmental impacts of these processes were assessed in collaboration with the local wastewater treatment plant, which carried out a detailed analysis of the wastewater coming from the entire Arzignano tannery district and compared it with that from the project processes.

These tests proceeded on the following lines:

design of the new processes and improvement/update of the required equipment;

testing and optimisation of the new processes from lab to industrial scale;

analysis of the process wastewater and sludges;

agronomic tests of the fertilisers produced from the recovered waste (trimmings, hair, clarified waste waters, sludge);

LCA analysis at water treatment level of the tannery wastewater; and

socio-economic analysis of the new processes.

These steps led to the validation of four new liming/tanning processes, with a lower environmental footprint and increased recycling possibilities. Significantly, the project demonstrated a chromium and formaldehyde-free tanning process with renewable organic enzymes. It also showed that the trimmings and recovered hair can be re-used to produce fertiliser.

The following environmental benefits were demonstrated:

up to 70% less water consumption due to bath recovery;

reduced consumption of chemicals (up to 80% of sulfates, 20% of chlorides and complete elimination; of chromium and formaldehyde compounds);

lower energy consumption (up to 10% less electricity and 10% methane);

lower waste production (up to 50% of the waste produced in weight can be recycled); and

reduced odorous emissions from the tannery district.

The achievements of the project have contributed to a wide range of EU legislation: the REACH Regulation, the Water Framework Directive, the Waste Framework Directive (Hazardous Waste, Circular Economy), the Clean Air Policy Package and the Energy Package. It also has implications for complying with the Kyoto Protocol and Paris Agreement on climate change.

Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).