PROJECT DESCRIPTION
BACKGROUND
An estimated 2.3 million tonnes of dyeing products are produced globally for the leather industry annually. Dyes are often chemically complex and heterogeneous in nature, which can present environmental hazard risks. Dyeing effluents released into wastewater can contain up to 50% of the dye used to set dye baths. Commercial dyes can thus constitute a significant source of heavy pollution. Eliminating contaminants from the leather industry’s dyeing effluents is a major environmental challenge, and one that is especially pertinent in Italy and Spain. These countries are home to the EU's largest leather industries, producing some 235 000 tonnes of leather goods every year.
OBJECTIVES
The BioNaD project’s main objective was to demonstrate the economic and environmental performance of innovative naturalised dyes for the leather industry. The project also planned to test bacteria-based degradation processes on dye effluent wastewater. It aimed to demonstrate the synthetic chemical design of dyes in compliance with EU REACH Regulation.
Specifically, the project planned to demonstrate the use of:
RESULTS
The BioNaD project developed and tested innovative naturalised dyes (NaDs) with the aim of reducing the chemical substances usually contained in acid dyes commonly used in tanneries. In this way, it provided an alternative to the conventional methods that commonly rely on acid dyes. The project also demonstrated that naturalised dye effluents can be purified through a bacteria-based degradation process.
The project team succeeded in synthesising NaDs in compliance with REACH Regulation. The NaDs were made using a prime colourant and lactose obtained from waste milk serum, thus avoiding the use of chemical additives. The NaDs were 90% purer than commercial, acid-base dyes. They are moreover water soluble and biodegradable, and their dyeing capacity compares well with their commercial counterparts. Furthermore, the use of lactose contributes to the recycling of disposable milk (10% of disposed milk can be recycled in order to produce naturalised dyes).
Pure blue dye, however, was unavailable in the marketplace and needed to be extracted from commercial colourants. A backup solution was outlined, and the project team achieved the expected results but with lower quantities of NaDs, and, consequently, a lower quantity of leather was treated. The NaDs were synthesised at a laboratory level before being produced on a larger scale. They were then tested on leathers at laboratory level, on a pilot scale using semi-industrial drums, and finally on a pre-industrial scale. Two tanneries, one in Spain and one in Italy, were used for the tests. Overall, the project team succeeded in treating 118 leather items (230 Kg total weight), and though these figures were below expectations, the pre-industrial validation of the process was achieved.
Treating the wastewater from the dyeing process with E.Coli was shown to be only partly successful, given that the blue NaD was unaffected by the bacteria. The project team solved the issue by studying biodegradation using fungi and was thus able to achieve good results, but only with the blue naturalised dye. As a result, the two processes were applied in a stepwise process in order to demonstrate full biodegradation of NaDs. Effluents were then treated on a pre-industrial scale with activated sludge in a close to real-life purification scenario succeeding in degrading residual naturalised dyes up to 90-95%. Another significant environmental implication is that between 50 and 75% of water can be recycled for dying processes allowing SMEs to reduce the consumption of water. This can be estimated at 1,000,000 m3 if at least 10% of the leather tanneries in the Italian industrial district use naturalised dyes.
The project’s method’s reduced environmental impacts were confirmed by a Life Cycle Assessment.
Due to the biodegradable nature of the naturalised dyes, the dyeing effluents could be easily recycled for successive dyeing cycles, thus reducing fresh water consumption by 50-75%. Furthermore, the biodegradability of naturalised dyes would drastically reduce the amount of waste generated from the whole retanning-dyeing phase by 45-50% of the effluents normally generated.
The dyeing process was moreover shown to reduce costs by around 10%, guaranteeing a good market uptake for the developed technology.
The naturalised dyes that were developed are in line the objectives of theREACH Regulation and the Waste Framework Directive, while the re-use of lactose, lower water consumption and efficient wastewater recycling treatment, also contribute to the Waste and Water Framework Directives and are in line with the Circular Economy Action Plan.
The main socio-economic effects of project activities were linked to a healthier working environment due to a reduced exposure to dyes and heavy metals. Furthermore the eco-friendly and biodegradable dyes will allow the tanneries and leather manufacturer to obtain the ECOLABEL certificates. This will result in extra benefits and positive image returns.
Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).
