Life cycle assessment of novel consolidants and a photocatalytic suspension for the conservation of the immovable cultural heritage

Abstract

Abstract Three innovative conservation materials were investigated by means of life cycle assessment (a calcium acetoacetate consolidant for carbonate surfaces, a TEOS-based consolidant for silicate substrates, and a photocatalytic suspension). So far not much attention has been paid to materials for the conservation of the built cultural heritage, with regard to their environmental performance. The main aim of this study was to assess the environmental footprint of the above-mentioned conservation materials which arises throughout their life cycle. In this way comparative data are made available for other future LCA studies on consolidants and photocatalytic suspensions. The most heavily polluting processes (i.e. “hotspots”) in the life cycle of the investigated conservation materials were identified, and, where possible, solutions for the further optimization of their environmental performance were proposed. In the case of life cycle of the two above-mentioned consolidants, the majority of emissions can be attributed to the synthesis of the constituent materials which are used to make the final products. Ethyl polysilicate is the largest contributor to the environmental footprint of the TEOS-based consolidant. On the other hand, in the life cycle of the calcium acetoacetate consolidant most of the environmental burdens are contributed by the synthesis of acetone-dicarboxylic acid. Around 0.47 kg of CO2 equivalent emissions affecting global warming are released to the air during the life cycle of 1 L of calcium acetoacetate (considering solely the upstream and core processes), whereas this value is higher in the case of the life cycle of the TEOS-based consolidant, i.e. 3.77 kg of CO2 equivalent emissions. In the case of the life cycle of the investigated photocatalytic suspension, although 1 L of this suspension is responsible for the release of only 0.1 kg of CO2 equivalent emissions over its life cycle (excluding the case-specific downstream processes) the heaviest environmental impact is caused by the production of packaging material (e.g. plastic buckets and other types of plastic containers). Taking into account the above-mentioned facts, there are not many possibilities for the reduction of the environmental burdens of the two investigated consolidants by the environmental optimization of the processes involved in the core and downstream stages of their life cycles. In the life cycle of the photocatalytic suspension, the environmental burdens related to greenhouse gas emissions could be reduced by more than 10% if a cleaner form of electricity production were to be adopted. A further aim of this paper is to promote sustainability in the field of management of the immovable cultural heritage. Although the described conservation materials have only a minor environmental effect in the field of the management of the immovable cultural heritage, the significance of sustainability is presented to conservators on a practical example.