This study aims to characterise and discuss the potential use of sediment from the Arkelstorp bay located in the south of Sweden. Sediments from the Arkelstorp bay is collected and analysed on nutrient content, age, and potential contaminants. No organic environmental pollutants are found and the metal content are not elevated but still problematically high. For example, the amount of cadmium per phosphorus is 480 mg Cd kg(-1) P. However, as the carbon 14-datings showed, the sediment is preindustrial. Therefore, the amount of registered cadmium comes naturally from the surrounding environment. Arkelstorp sediments present the potential to become a source of nutrition in agriculture. The results show that the material is a good source of nutrients, with a nitrogen content of 18 g kg(-1) dry matter (DM), phosphorus 0.8 g kg(-1) DM and potassium 2.4 g kg(-1) DM respectively. However, the metal content is problematic to use the material without any pre-treatment. On the other hand, bioenergy production is expected to increase in the future, where this resource could potentially be helpful for the cultivation of bioenergy crops.

Dredging of sediments is conducted worldwide to maintain harbours and water bodies. As a result, large amounts of materials generated require proper management and could have useful applications in a circular economy context. The current use of peat as organic material in cultivating plants requires urgent replacement by more sustainable alternatives. In this context, using nutrient-rich sediments generated by dredging could be an attractive option. However, due to contaminants in dredged sediments, more investigations are required. The present study investigated the potential to employ dredged material as a plant-growing substrate to cultivate lettuce (Lactuca sativa). The study employed compost and dredged sediments from Malmfj & auml;rden Bay, Sweden, with low and high nutritional content(LN and HN, respectively), with and without polymer (PO) used for dewatering. The tests were carried out under con-trolled conditions in a greenhouse, and the studied substrates were (% vol): (1) 100 % sediment (100S(HN)); (2) 50 %sediment +50 % compost (50S(LN)-50C); (3) 70 % sediment +30 % compost (70S(LN)-30C); (4) 50 % polymer sediment+50 % compost (50S(PO)-50C);and (5) 100 % compost (100C). Fertilisers were added to 50S(LN)-50Cand 70SLN-30C during the experiment. Lettuces with the highest weight were harvested from substrates 100C, 50S(PO)-50C and 50S(LN)-50C.However, the lettuces only reached a weight of 18.57 +/- 4.67 g. The results showed that a main limitation of the growth was probably a lack of aeration of the sediments during sampling and development of the experiment. The low aeration possibly caused a lack of available forms of N in the substrates, hindering the growth. Lettuces harvested from substrates containing sediments presented Cd concentrations slightly overpassing the Swedish thresholds, and the health risk index was marginally exceeding 1. Hence, sediments need to be pre-treated before using them to cultivate edible crops, or they could be employed to cultivate ornamental or bioenergy plants

The management of dredged sediments is a challenging issue since it involves the interconnection of complex economic, social, technical and environmental aspects. The EU LIFE SUREproject aimed to apply a more sustainable dredging technique to Malmfjärden Bay in Kalmar/Sweden(a shallow urban water body with a high content of nutrients) and, additionally, it involved beneficial uses for the dredged material, in line with the circular economy concept. To achieve this, a life cycle assessment (LCA) study was carried out to assess the potential environmental impacts associated with two scenarios: sediment landfilling (S1) and soil conditioning (S2). This LCA study also aimed to evaluate and compare the costs related to each scenario. S1 contemplated the construction and operation of the landfill for 100 years, including the collection and discharge of leachate and biogas. S2 included the use of sediments in soils and the avoidance of producing and using fertilisers. Results showed that (S2) soil conditioning (total impact: −6.4 PE) was the scenario with fewer environmental impacts and the best economic evaluation. The S2 scenario was mainly related to the positive environmental savings produced by reducing fertiliser consumption (which also avoided purchase costs). However, S2 was also linked to potential negative effects associated with eutrophication and toxicity categories of impacts due to the possible spread of nutrients and pollutants in terrestrial and aquatic environments. In order to mitigate this problem, the sediments could be pre-treated to reduce their risk of pollution. Moreover, the main impact of the landfilling scenario(S1, total impact: 1.6 PE) was the emission of global warming-contributing gases during the operation of the facility. Implementing the soil conditioning scenario was therefore recommended, in line with the aim of the LIFE SURE project. Finally, it was recommended that LCA studies should be applied more often in the future when selecting beneficial uses for dredged sediments. The decision-making process is facilitated when the positive and negative impacts produced by each handling option are considered.

Dredging of sediments occurs worldwide to increase water depth in harbours, bays, lakes and rivers, as well as to recover aquatic ecosystems. Landfilling and open-ocean discharge are traditional disposal routes for dredged material. However, the methods are restricted by environmental and legal concerns. Using dredged sediments for beneficial uses can contribute to implementing circular economies and avoiding traditional disposal methods. This thesis aimed to contribute to the sustainable management of dredged sediments by increasing the knowledge of the beneficial use of the material. The work focused on Malmfjärden bay, located in Kalmar, Sweden, which is currently shallow and presents a high concentration of nutrients. The LIFE SURE project aimed to dredge the bay and use the dredged material for beneficial purposes.

The results from the thesis showed a high potential to use Malmfjärden sediments for beneficial uses. The first step involved the characterisation of sediments, which showed a medium-high content of N and P was also present. The main pollution concerns were As, Pb and Cd, since their contents overpassed the Swedish limits for sensitive uses. The speciation and extraction of elements were also performed to assess their risk of pollution. The results showed that the most labile elements were Zn and Pb, and both presented the highest extraction rates using EDTA and EDDS. The results showed that the chemical extraction of metals could contribute to treating metal-polluted sediments and become a mining technique. Further studies focused on the recovery of nutrients from the sediments. They were mixed with compost, and lettuce grew in different substrates. However, the plants prematurely stopped growing, possibly due to the lack of available forms of N. Moreover, the harvested lettuces overpassed permissible contents for Cd, slightly threatening human health. It was shown that dredging could provide nutrients to soils, but the risk of metal pollution should be assessed. Finally, a life cycle assessment was calculated to assess the environmental impacts associated with landfilling Malmfjärden sediments or using the material in soil conditioning. Both scenarios presented negative impacts on global warming, eutrophication and toxicity categories. However, soil conditioning showed the most positive score due to the environmental savings of avoiding the production and use of fertilisers.

The thesis concludes by encouraging the performance of more interdisciplinary projects. This could combine the knowledge from several sectors to enhance the implementation of the beneficial use of dredged sediments.  

Worldwide, sediments are dredged from water bodies to guarantee proper water levels and remediate aquatic ecosystems. Dredged sediments contain metals that could interfere with recycling if the concentrations overpass permissible limits. Washing of elements from sediments represents a technique to decrease the concentration of metals, and it could introduce a new source of elements. The current study aimed to employ ethylenediamine-tetraacetic acid (EDTA) and ethylenediamine-disuccinic acid (EDDS) and investigate the effect of operational parameters (concentration and pH) on the chemical extraction of metals from dredged sediments. Core sediments were extracted from sampling stations around Malmfjärden bay, Sweden. The results suggested that lead, zinc and copper were the elements with higher extraction rates, followed by arsenic and nickel. Chromium was poorly extracted. EDTA was more efficient than EDDS in dissolving the elements. Moreover, acidic conditions offered higher extraction rates for As using both chelators and for Pb employing EDTA. The 0.05 M concentration presented a higher mean extraction rate than 0.01 M for Cu, Cr and Ni for EDTA and EDDS. The findings in this study suggest that sediment washing is a promising technique to decrease metal concentrations in sediments and enhancing the feasibility to use the material for beneficial uses.

Contamination associated with metals is a critical concern related to their toxicity, persistence, and bio-accumulation. Trace elements are partitioned into several chemical forms, which some are more labile during fluctuations in the environment. Studying the distribution of metals between the different chemical fractions contributes to assess their bioavailability and to identify their potential risk of contamination to surrounding environments. This study concerns the speciation of metals (Pb, Cr, Ni, Zn and Fe) from sediments coming out from Malmfjärden bay, Sweden. The aim was to assess the potential risk of metal pollution during present and future dredging as well as while using dredged sediments in beneficial uses. The Tessier speciation procedure was chosen, and the results showed that low concentrations of metals were associated with the exchangeable fraction. In contrast, the major concentrations were linked to the residual part. The risk indexes (contamination factor and risk assessment code) showed that, during dredging activities, there is a low concern of pollution for Cr, Ni and Fe and a medium risk for Pb and Zn. Additionally, in all elements, the sum of non-residual concentrations was below the Swedish limits for using dredged sediments in sensitive lands. The findings suggested that the investigated metals in Malmfjärden sediments are related to low risks of spreading during using in beneficial uses.

Biomass is defined as organic matter from living organisms represented in all kingdoms. It is recognized to be an excellent source of proteins, polysaccharides and lipids and, as such, embodies a tailored feedstock for new products and processes to apply in green industries. The industrial processes focused on the valorization of terrestrial biomass are well established, but marine sources still represent an untapped resource. Oceans and seas occupy over 70% of the Earth's surface and are used intensively in worldwide economies through the fishery industry, as logistical routes, for mining ores and exploitation of fossil fuels, among others. All these activities produce waste. The other source of unused biomass derives from the beach wrack or washed-ashore organic material, especially in highly eutrophicated marine ecosystems. The development of high-added-value products from these side streams has been given priority in recent years due to the detection of a broad range of biopolymers, multiple nutrients and functional compounds that could find applications for human consumption or use in livestock/pet food, pharmaceutical and other industries. This review comprises a broad thematic approach in marine waste valorization, addressing the main achievements in marine biotechnology for advancing the circular economy, ranging from bioremediation applications for pollution treatment to energy and valorization for biomedical applications. It also includes a broad overview of the valorization of side streams in three selected case study areas: Norway, Scotland, and the Baltic Sea.</p>

The CONTRA- Baltic Beach Wrack- Conversion of Nuisance to a Resource and Asset project aims to transform Beach Wrack into a Resource. In collaboration with CONTRA project, the Environmental Science and Engineering Group (ESEG) aims to demonstrate the technological and economic feasibility of using beach wrack raw materials for energy production and bio-based compost as practical approaches towards the circular economy. In the present study, the purpose is to concentrate the nutrients from four different biological materials (beach wrack, sawdust or wood chips, degraded sediments and Coffee powder), through the composting process.