Circular economy in extractive industry: challenge and chance to recover fine particles produced in marble quarries exploitation

Stone industry plays a significant role in the global economy. The 2015 production was placed in the order of 82.6 million tons with a percentage of the waste extraction and processing amount to over 70% of the gross quantity. Carbonate stones (such as marble, limestone and travertine) account for 58 % of the whole production of dimension stone, serving as primary materials for construction and ornamental uses since ancient times. Approximately 50% of waste is generated during mining operation and around 15% during processing. The disposal of marble powder, a very fine material produced by the marble industry, is one of today's global environmental problems affecting stone industry. Even if the ultra-fine calcareous particles contained in marble sludge have applications in most major industries, thanks to their chemical and physical characteristics, in most cases these materials are landfilled because of the difficulties in recovering, mainly related to local legislation and lack of appropriate protocols.
The need to reduce the use of non-renewable natural resources and, at the same time, to minimize the negative impacts on the environment, has led to an increasing interest in recovery and recycling, in line with the expressed EU policy in the Europe 2020 strategy to reduce Europe's efficiency and in the EU strategy for sustainable development. The Carrara marble basin is one of the most emblematic cases in the Italian stone industry, and it includes about one hundred quarries of colored and white marble, exploited from Roman times. Even if the new technologies have improved efficiency in quarrying and reduced the production of waste, around 50% of the extracted marbles in the Carrara basin still result in waste. Modern cutting technologies generate greater amount of finer materials and sawing residue, varying in size from sand to silt. Due to this very fine particle, it’s easy to see how this characteristic can cause problems with the stability of landfills, with consequent difficulties for their management. The aim of this research is to provide a comparison between different characteristics of marble fine waste in Carrara, both sludges deriving from quarry-cutting and stone processing, to demonstrate the feasibility of their recovery and utilization in different industrial application (i.e., mineral fillers, high value-CaCO3 products, building sector). The results obtained from analysis are promising and could lead to a possible reuse of the materials, in line with the circular economy approach. The reuse of marble waste can bring the double benefit of giving a new value to this by-product and, at the same time, partially eliminate the environmental problem caused by it. The combination of all these insights could lead to sustainable mining of the ornamental stones industry.