Phosphorus mining from eutrophic marine environment towards a blue economy: The role of bio-based applications.

Global phosphorus reserves are under pressure of depletion in the near future due to increased consumption of primary phosphorus reservoirs and improper management of phosphorus. At the same time, a considerable portion of global marine water bodies has been suffering from eutrophication due to excessive nutrient loading. The marine environment can be considered as a valuable phosphorus source due to nutrient rich eutrophic seawater and sediment which could potentially serve as phosphorus mines in the near future. Hence, sustainable phosphorus recovery strategies should be adapted for marine systems to provide phosphorus for the growing market demand and simultaneously control eutrophication. In this review, possible sustainable strategies for phosphorus removal and recovery from marine environments are discussed in detail. Bio-based strategies relying on natural phosphorus uptake/release metabolism of living organisms are suggested as promising options that can provide both phosphorus removal and recovery from marine waters for achieving a sustainable marine ecosystem. Among them, the utilization of microorganisms seems promising to develop novel strategies. However, the research gap for the technical applicability of these strategies is still considerably big. Therefore, future research should focus on the technical development of the strategies through laboratory and/or field studies. Coupling phosphorus mining with other valorisation pathways (i.e., metal recovery, energy production) is also suggested to improve overall sustainability and economic viability. Environmental, economic and societal challenges should altogether be well addressed prior to real scale applications.

Drivers and Barriers for Implementation and International Transferability of Sustainable Pop-up Living Systems.

In the current urban system, characterised by a one-directional flow of resources from the rural environment to the cities, the construction sector plays a critical role in supporting the transition from a linear to a circular economy. In this framework, temporary pop-up environments act as an innovative and sustainable type of living system. These are structures conceived as temporary from the outset, based on characteristics like flexible light-weight technologies, fast and easy assembly operations, temporary occupation of the ground and adaptability to different uses, needs and target groups. Great importance is placed on construction reversibility and environmental sustainability. In the framework of the interdisciplinary research project 'Urban Pop-Up Housing Environments and Their Potential as Local Innovation Systems', six scenarios of application for temporary pop-up environments for the city of Vienna have been developed, taking into consideration technical, urban and social aspects, on the basis of local uses and climatic conditions. In order to explore drivers and barriers of the scenarios regarding the transferability of the concepts, online questionnaire sessions were conducted with an international audience. The feedback obtained by the participants allowed an analysis of the applicability of the concepts to other urban environments under comparable conditions at the international level. The paper presents the results obtained from the questionnaire sessions, allowing insight on the international perception of temporary pop-up environments and, specifically, strengths and weaknesses of the scenarios, as well as their possible applicability in the local contexts of the respondents. It was observed that while the perceptions of what requirements temporary housing must fulfil in order to be sustainable are quite uniform among the experts, the identified barriers for implementation within the different international contexts differed greatly. The designs of these temporary housing scenarios, which rely heavily on local resources and systems, are strongly interwoven with the fabric and conditions of the city they were conceptualised for. While this serves to promote the sustainability of these solutions, it poses a particular challenge for the international transferability, requiring heavy adaptation for other contexts.

Waste or substrate for metal hyperaccumulating plants - The potential of phytomining on waste incineration bottom ash.

Phytomining could represent an innovative low-cost technology for the selective recovery of valuable trace elements from secondary resources. In this context the potential of phytomining from waste incineration bottom ash was tested in a pot experiment. Fresh bottom ash was acidified, leached to reduce salinity and amended with organic material to obtain a suitable substrate for plant growth. Two hyperaccumulator species, Alyssum serpyllifolium subsp. lusitanicum and Sedum plumbizincicola as well as three metal tolerant species, Brassica napus, B. juncea and Nicotiana tabacum were tested for their phytomining potential on the pre-treated and amended bottom ashes from municipal solid waste and hazardous waste incineration. The hyperaccumulators had severe difficulties to establish on the bottom ash and to produce sufficient biomass, likely due to salinity and Cu toxicity. Nevertheless, concentrations of Ni in A. serpyllifolium and Zn in S. plumbizincicola were high, but total metal removal was limited by the low biomass production and was clearly less than on metalliferous soils. The Brassica species proved to be more tolerant to salinity and high Cu concentrations and produced considerably higher biomass, but total metal removal was limited by rather low shoot concentrations. The observed limitations of the phytomining process along with currently low market prices of Ni and Zn suggest that further optimisation of the process is required in order to make phytomining economically feasible on the tested waste incineration bottom ashes.