Cradle-to-gate study of red clay for use in the ceramic industry

Abstract

Background, Goal and Scope

The ceramic tile industry is one of the most important industries in Spain, with the highest concentration of firms to be found in the province of Castellón on the Mediterranean coast. The basic input material for this industry is red clay. The aim of this study was to carry out an LCA of the process of mining, treating and marketing this clay in order to identify the stages and unit processes that have the greatest impact on the environment.

This LCA examines all the stages of the red clay from cradle to the customer’s gate, including the process of mining and treating the clay in the mining facilities and its later distribution to end users.

Methods

Life cycle inventory (LCI): An exhaustive LCI was performed by collecting data from the mine run by Watts Blake Bearne Spain, S.A. (WBB-Spain) in Castellón. Inputs and outputs were collected for all the unit processes involved in the mining, treatment and marketing of the clay:

• Mining the clay, which embraces the unit processes of removing the layer of vegetation covering the chosen area, preparing the area to allow access for the firm’s vehicles, and boring or blasting the place the clay is to be extracted from.

• Treating the clay that is mined to make the finished product, which entails all unit processes required to separate out the waste material and transport it to the tip (which will later be reconditioned), excavating and transporting the clay to the crushing plant and later storing it in heaps before delivery to customers. All the internal transport that takes place between each unit process has also considered.

• Distribution of the final product, where the clay is loaded onto dumper trucks and delivered to the customer.

Life cycle impact assessment (LCIA): According to ISO 1404X standards, the LCIA is performed at two levels. Firstly, the emissions accounted for in the inventory stage are sorted into impact categories to obtain an indicator for each category (mandatory elements). Secondly, the weighting of environmental data to a single unit is applied (optional elements). In compliance with ISO 14042, a sensitivity analysis is performed and three different impact assessment methods (Eco-Indicator’95, Eco-Indicator’99 and EPS’2000) are applied in order to analyse their influence on the results.

Results

The processes that involve the movement of clay within the mine (excavation and loading and transport to the crushing facilities and heaps) are the ones that make the greatest contribution to impact categories for pollutant emissions. As weighting methods in LCA remain a controversial issue, a recommendation when robust results are required, can be to use several methods to examine the sensitivity of the results to different values and worldviews. In our application case, in spite of the differences between the three impact assessment methods applied (Eco-Indicator’95, Eco-Indicator’99 and EPS’2000), the same conclusions can be established from the environmental point of view and we can conclude that the ultimate results are not sensitive in the transformation of mid-points to end-points.

Discussion

Taking into account the characteristics of the product being analysed, in addition to the impact categories for pollutant emissions that are traditionally considered in LCA studies, environmental parameters related to resource use (fuel, electricity and water consumption), waste generation (dangerous and non-dangerous wastes) and land use (natural resource appreciation and land use efficiency) and its later rehabilitation (degree of rehabilitation) have been defined. These parameters can be used as additional criteria for an environmental product declaration or criteria for a future eco-labelling of red clay.

Conclusion

The results of this study made it possible to identify the unit processes that make the greatest contribution to environmental impact that being, specifically, excavation and loading and transport to the crushing facilities and heaps. Such processes are directly related to the fuel consumption, category that faithfully reproduces the environmental profile of most of the impact categories related to pollution emissions. Special interest has the consideration of additional parameters to quantify the land use and its later rehabilitation.

Recommendations

The ceramic tile industry has a basis to market and promote tile products with improved environmental impacts. Given that transport and extraction are dominant underlying issues, it is quite likely that such environmental improvements are also win-win in the economic sense. The availability of exhaustive life cycle inventories is the key to allow this industry to, rapidly, incorporate LCA during product development. Complimentary life cycle costings would also be relatively minimal in terms of effort.

Perspectives

Although this study performs the LCI for the basic raw material (clay), future studies should be conducted to complete an LCI for the remaining elements employed by the ceramic tile industry, with the aim of developing a characteristic LCI database for this industry. This includes data on raw materials (feldspar, silicious and feldspars sand, boron, glaze, frit, etc.) and processes (enamelling, firing, water waste treatment, etc.).