PSI - Issue 55

Poliana Bellei et al. / Procedia Structural Integrity 55 (2024) 96–102

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Poliana Bellei et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1. Introduction Aquaculture is an ancient practice that has evolved over the centuries according to the knowledge acquired by farmers based on needs and also on their positive and negative experiences. In 1950 the total production of fisheries and aquaculture reached 19 million tons; almost 70 years later, this value reached a historic record accomplishment of 179 million tons in 2018 with an annual growth of 3.3% (FAO. 2022). In Portugal, the production of mollusks in aquaculture increased by 48% in 2020, representing 58% of the total aquaculture production. In 5 years (2015 to 2020) oyster production tripled in Portugal. Oysters were the most relevant species (3,838 tons), followed by clams (3,659 tons) and mussels (2,007 tons) in 2021 (DGRM. 2021). From the perspective of aquaculture production, Algarve is the most representative region in Portugal, being responsible for 42% of the production sales volume and production value of around 157 M€ (2020). Most of the nurseries for the production of bivalves are located specifically in the Ria Formosa. The high production volume of this product is due to the good conditions for cultivation, such as the warmer water temperature (DGRM. 2021). The consumption of bivalves is part of Portuguese gastronomy and its role in the national industry is considerable. This fact is due not only to the production of a high number of species, but also to the number of people who depend directly on this sector, through the harvesting and commercialization. The practice in this sector generates a large production of shellfish waste, and the slow process of shell degradation increases the volume of this waste, making reuse more important (Félix et al. 2018). Based on the current reality, the final destination for oyster shells is incineration, which carries environmental impacts. Due to incineration high costs, often dead oysters are left in the nurseries or in surrounding areas: The accumulation of shells leads to unpleasant odors, reduces the quality of life for individuals (Mo et al., 2018), and increases oyster farmers concerns due to the occupation of space near fishing sheds and the lack of options for reuse. These reasons often lead to the inappropriate use of shells, or negative effects on local environment. With the principle of safeguarding goods from the ocean, the blue economy concept surfaced in 2012, intertwined with the circular economy, which emphasizes sustainability and the recycling of waste, along with various other sustainable practices that utilize and preserve marine and coastal resources (Eikeset et al. 2017). It is possible to find previous studies (Magalhães et al. 2024) that report the use of oyster shells in mortars hundreds of years ago in coastal regions (Razali et al. 2017). Laefer (2004) says that lime had to be produced using oyster shells, because limestone was scarce. Therefore, coastal regions took advantage of the availability of this material to incorporate it into mortars. The reports even claim that this mortar was more durable. Historically, shells were used in mortar mixing to make a specific type of material, using local resources and part of the vernacular architecture of each place (Hodges. 2022). The addition of local products in mixtures for civil construction dates back to an ancient period (before Christ), and at that time the materials used were natural. Lime based products have been used since very early times in the history of civilization. The type of lime varied according to the availability of materials in each region, with oyster shells being used in seaside places and calcium and magnesium rocks such as chalk, dolomite and limestone in other places (Guimarães. 2002; Chandra. 2003). Guedes (2018) through a European vision, reports that the Portuguese adopted construction techniques originating from Indian culture, due to their trips to India in the 16 th century. The Indian technique used to mix and grind ingredients to make the lime mortar known as Chunam . According to the author, the mixture might have a Greco Roman origin as well and the use of softening lime mortar joining shells, sand and other materials has multiple origins in Europe and Asia. The recipe was well accepted at the time in places like Mozambique, Brazil and Macau. Currently, society's great challenge is to face climate change and mitigate environmental impacts and the incorporation of shells is a promising sustainable solution of reusing waste while creating a durable product in the construction sector. The present work aims to identify the environmental impacts of recovering traditional construction techniques in coastal regions by incorporating oyster shells into mortar towards to a blue circular economy. The possible environmental impacts are measured using Life Cycle Assessment. Life Cycle Assessment (LCA) is a methodology that aims to identify the significance of the potential environmental impacts of a given product at various points in its life cycle, assisting in strategic planning, definition of priorities, project or design of products or processes. The LCA intends to analyze the product from the beginning to the end of life, starting from the acquisition of raw materials, production, use, end-of-life treatment, recycling and disposal (ISO 14040. 2006).