Bivalves aquaculture is already considered a very sustainable for of food production and might become an essential pillar on which to develop future global food security. However, with the increase in production, a correspondingly great amount of waste will be produced all around the earth, principally in the form of shells, which can represent up to 90% of the fresh mollusk weight. Nowadays, shell waste has no notable use and is commonly regarded as waste, often dumped in landfill, or thrown back into the sea, causing a significant level of environmental concern, and resulting in a loss of natural and valuable resources. Bivalve shells are mainly formed by CaCO₃, giving them the potential to become a promising secondary raw material for several applications, from a circular economy perspective. This paper aims to review the scientific literature of the last twenty years and the principal recent trends in shell waste reuse, describing applications that are already in place on a large scale in agriculture and livestock, soils, water and wastewater remediation, biodiesel production and biofilters, as well as niche applications that now simply have the potential to be scaled up.

The Pacific oyster Crassostrea gigas is one of the world’s most cultivated and prized molluscs. Although it is usually considered a luxury product, it meets all the requirements to be included in a sustainable diet, and its production and consumption have great potential for growth in the coming years. Oyster farming is a worldwide activity, with China and France as the main producers, but recently, the possibility of implementing the Italian production, mainly focused on clams and mussels, has been considered an interesting issue, especially due to the growing local and global demand. The present study has been carried out by collecting data from the Sacca di Goro, north-east Italy, the most important national mollusc farming area. Life cycle assessment (LCA) methodology was applied to two different farming scenarios in order to improve the overall sustainability of the process. Using OpenLCA™ software (GreenDelta, Berlin, Germany) and the ReCiPe^® midpoint (H) v.1.12 method, the environmental impacts of the traditional Italian farming technique, carried out entirely offshore in longlines, and the alternative option, in which the oyster seed pre-fattening phase was carried out in the lagoon, were calculated and compared. The results show that replacing the current pre-fattening phase with pre-fattening in a lagoon reduces CO₂ emissions by approximately 12% and all other impact categories by approximately 9%. In addition, non-recyclable plastic materials and fuel consumption emerged as the main environmental hotspots.

Wetlands possess intangible values that are usually overlooked in decision-making processes. Based on questionnaire surveys, this work aims to quantify both the non-use and cultural values provided by the different wetlands of the Po Delta Park (Northern Italy), selected as ideal case study, using willingness to pay (WTP) for wetland conservation and travel cost methods, respectively. Their relationships with socio-economic variables and respondents' preferences for current and future use were also analysed. The 61.39% of participants were willing to pay a mean amount of 95.8 € (±40). The average travel cost was 38.68 € (±6.24), with higher values observed for environmental experts than for other citizens. Wetlands differ significantly in travel costs, current and future use, but not in WTP. Poisson regressions showed that non-use and cultural values were significantly dependent on personal information, preference variables and travel distance. Intangible dimensions, such as bequest and existence values, showed higher valuations/rates than option and direct use values. The results highlight that perceptions of the intrinsic value of nature are influenced by demographic characteristics, distance from the area and desired future uses. Non-use values seem abstract and generalised to the whole area, regardless of the ecological characteristics of the wetland, even though a significant relation to wetland uses was observed. In contrast, cultural values are tied to specific wetlands, as indication of the importance of historical relationships between people and nature. Such findings underline that the different dimensions of intrinsic value of nature may act at different scales and help decision-makers to incorporate such values into environmental accounting.

Aquatic vegetation loss caused substantial decrease of ecosystem processes and services during the last decades, particularly for the capacity of these ecosystems to sequester and store carbon from the atmosphere. This study investigated the extent of aquatic emergent vegetation loss for the period 1985–2018 and the consequent effects on carbon sequestration and storage capacity of Valle Santa wetland, a protected freshwater wetland dominated by Phragmites australis located in the Po river delta Park (Northern Italy), as a function of primary productivity and biomass decomposition, assessed by means of satellite images and experimental measures. The results showed an extended loss of aquatic vegetated habitats during the considered period, with 1989 being the year with higher productivity. The mean breakdown rates of P. australis were 0.00532 d⁻¹ and 0.00228 d⁻¹ for leaf and stem carbon content, respectively, leading to a predicted annual decomposition of 64.6% of the total biomass carbon. For 2018 the carbon sequestration capacity was estimated equal to 0.249 kg C m⁻² yr⁻¹, while the carbon storage of the whole wetland was 1.75 × 10³ t C (0.70 kg C m⁻²). Nonetheless, despite the protection efforts over time, the vegetation loss occurred during the last decades significantly decreased carbon sequestration and storage by 51.6%, when comparing 2018 and 1989. No statistically significant effects were found for water descriptors. This study demonstrated that P. australis-dominated wetlands support important ecosystem processes and should be regarded as an important carbon sink under an ecosystem services perspective, with the aim to maximize their capacity to mitigate climate change.

Brackish lagoons are highly productive systems that support fishing and aquaculture activities with important revenue. At the same time, they function as fundamental habitats for the conservation of a number of species that use lagoons for reproduction and feeding. The present study aims at describing the seasonal structural and functional variations of fish communities in the Fattibello lagoon, a small but important nursery ground of the Po River delta (northern Italy), historically exploited for fishing. The fish community was sampled monthly over a six-years’ period (2009–2014). The results were normalized in catch per unit of effort (CPUE) and are expressed both as individual abundances (ind/CPUE) and biomass (g/CPUE). Higher biodiversity levels were observed in autumn, when both lagoon residents and marine species coexist, and summer, for individual abundances and biomass. Biomass was a better descriptor than individual abundance of the functional use of the lagoon. In autumn, the lagoon resident species increased significantly, while marine feeding ground species decreased. Vice versa, lagoon residents decreased in winter, when the lagoon were mainly used as feeding ground by marine fishes. Marine migrating species were present throughout the whole year. Overall, the lagoon serves as (i) reproduction habitats for different species, as well as habitat for the pre-reproductive period for the European anchovy; (ii) nursery grounds for a number of commercial species; and (iii) habitats for lagoon resident species, supporting them for the whole life cycle. Overall, the results highlight the fundamental conservation role of the lagoon throughout the whole year, and that seasonal structural and functional patterns of fish communities should be carefully considered when seeking to harmonize direct uses, such as fishing and bivalve farming, as well as nature conservation.

Oyster farming plays a crucial role in sustainable food production due to its high nutritional value and relatively low environmental impact. However, in a scenario of increasing production, it is necessary to consider the issue of plastic use as a limitation to be addressed. A life cycle assessment (LCA) was conducted on oyster farming in La Spezia (Italy) as a case study, utilizing 1 kg of packaged oysters as the functional unit. Fossil-based plastics and wooden packaging were identified as the primary environmental concerns. To analyze potential strategies for reducing the environmental impact of oyster farming, alternative scenarios were considered wherein fossil-based materials were replaced with bio-based materials. Specifically, this study examined the substitution of the current packaging, consisting of a wooden box and a polypropylene (PP) film, with a fully recyclable PP net. Additionally, polylactic acid (PLA), polyhydroxyalkanoates (PHAs), and bio-based polyethylene terephthalate (Bio-PET) were proposed as alternatives to virgin high-density polyethylene (HDPE) and PP for buoys, oyster bags, and boxes. Among the scenarios analyzed, the sole effective strategy to reduce the impact of plastics on the process is to replace them with PHA. In the other cases, the high energy consumption of their non-optimized production renders them disadvantageous options. However, the assessment must include the effects of degradation that traditional plastics can have in the marine environment, an aspect that potentially renders natural fibers more advantageous. The use of PP net packaging has demonstrated high efficacy in reducing impacts and provides a foundation for considering the need to combine sustainability and marketing with current legislation regarding food packaging.