Application of life cycle assessment to the production of man-made crystal glass

This paper presents a life cycle assessment (LCA) of the manufacturing process of crystal glass products in order to evaluate the potential environmental impacts due to a crystalware company located in Colle di Val d’Elsa, Siena (Italy). Since there is not any published research specifically focussed on crystal production to our knowledge, outcomes from this study would represent a first documented evidence gathered from an LCA of crystal glass products. Once a detailed description of the production process was provided, different categories of impacts were assessed and analysed. Outcomes allowed us to identify ‘weak points’ in the production process and propose possible solutions for decreasing the risk of negative effects on the environment.

According to the LCA methodology, the whole life cycle of crystal glass was structured into four primary phases—raw materials acquisition, crystal glass manufacturing, product utilisation and final disposal—each of which includes a set of sub-processes. Through an accurate life cycle inventory, primary data, relative to the year 2006, were elaborated through the EDIP database. The calculation of impacts was aided by GaBi4 software with reference to a functional unit corresponding to 1 kg of crystal glass products. Relative to the CML2001 problem-oriented approach, a set of impact categories was used for the classification and characterisation of the life cycle impact assessment. Potential category indicators were finally accounted for and normalised in accordance with the CML Western Europe method.

The following ten impact categories were assessed: (1) depletion of abiotic resources, (2) acidification, (3) eutrophication, (4–6) ecotoxicity (marine and freshwater aquatic as well as terrestrial, respectively), (7) climate change (greenhouse effect), (8) human toxicity, (9) stratospheric ozone depletion and (10) photo-oxidant formation. Results showed that among the main phases, crystal glass manufacturing is the one with the highest environmental impact and emissions to air, mainly due to an intensive use of energy and materials. In particular, some sub-processes within the manufacturing stage, such as melting in furnaces, acid polishing, cutting and forming, were found to hold a high responsibility for most of the environmental effects. The main effects depend on CO₂, NO_x and SO₂ emissions, heavy metals emissions and use of non-renewable resources. In particular, the latter is due to the processes of extraction, refining, transport and use of fuels such as natural gas.

Results were analysed relative to each of the main processes involved in the crystal glass life cycle and critical points were investigated in order to inform the administrators of the crystalware company and address future choices towards a more sustainable production. Some technical solutions were proposed in order to improve environmental performances. Impacts due to the use of lead in the mixture were widely treated in literature and briefly discussed here.

An accurate energy and material flow inventory allowed us to assess the potential environmental impacts of the crystal glass production in Colle Val d’Elsa, including the effects of processes occurring within the industrial plant and those due to the import of products and services from outside. Through the case study, we aimed to provide an exhaustive description of the main steps in the process and clear results relative to different impact categories. Outcomes showed that some procedures could be implemented in order to decrease these impacts. The use of lead is an irreplaceable characteristic of crystal products, but also a critical point to deal with. Nevertheless, the high quality of man-made crystal products makes the use of lead acceptable. The LCA of crystal glass products presented in this paper provided an accurate description of processes and procedures that can mirror a traditional production in a broader sense. This paper can therefore represent a valuable reference for future studies on crystal glass production processes.

The LCA method was performed for identifying critical aspects in the production process from an energetic and environmental viewpoint and was useful for constructing a model of the crystal glass production in Colle di Val d’Elsa. This can be a starting point for processing an environmental product declaration.