by Giorgio Pozza, Andrea Loi, Gruppo Mastrotto
The research undertaken by Gruppo Mastrotto consisted principally in the development of experimental evidence relating to the processes of interest and in the evaluation of the results according to criteria as objective as possible. In the first stage it has been considered a “pilot” scale to transfer later on the best results on industrial scale.
For a comprehensive evaluation of the experimentation, basic parameters have been defined whose purpose is to express the commodity evaluation (Product IG Index, for leather) as well as an environmental evaluation (Environmental Index IA, for process) using a numeric value. At this point, mediating between both the IA and the IG indexes, it leads to the definition of a third index, called Life Index (IL), in accordance to the project within which it has been defined. Generally speaking, use of indicators is intended to facilitate the understanding of experimental process and planning the future working processes. The IL assessment, then, is able to provide an overview of the course of an experiment, both from a point of view of product quality, both from the environmental impact of the process.
The results achieved
In the following graphics there are some experimental data obtained in the course of the project. In this case we consider the three approaches to reduce the environmental impact applied synergistically (hair recovery, recovery of liming bath, reduction of chemicals used).
In summary, the main points considered in the research are:
- The recovery of the process water used in liming:
An operation easily to be industrialised, which if optimised on industrial process would allows a considerable water saving without causing significant lowering in the product quality.
- The recovery of the cattle hair during the depilation phase:
This is an approach that leads to a significant reduction in discharged pollutants in wastewater and to obtain a by-product with great potential for recycling and reuse. It is also easily applicable to industrial production.
- The reduction of chemical used during processing:
Here we consider the progressive decline in the use of sulfide and sodium hydrogen sulphate in the liming operations, noticing that there might still be room for improvement compared to the current state of the art. Specifically, it was possible to achieve a reduction of the sulfide input of about 19%.
- The use of indexes for the definition of an objective and computable assessment tool in the tanning process.
- Obtaining a by-product (cattle hair) with a potentially high added value together with the decrease of the pollution load in wastewater.
- A progressive decrease in the use of chemicals, with a conseguent reduction of pollution in the waste.
- Decrease of water consumption per kg of leather soaked by recovering process bath.