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Insights to beachcast management on Gotland, Sweden: An Industrial Ecology perspective on waste-resource ambiguity
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Water and Environmental Engineering.
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Beachcast or beach wrack, washed-up algae and seaweed, used to be a highly sought-after agricultural resource (fertiliser and soil conditioner) in coastal communities around the world before being replaced by chemical fertilisers, but considering the talks of a circular bio-economy – can we reintroduce it? 

Since the abandonment of beachcast in agriculture, the amount of beachcast has significantly increased as an effect of eutrophication caused by the use of chemical fertiliser, and the material is commonly considered waste. Meanwhile, soils have degraded and need the multiple positive effects on agroecosystems that beachcast could provide. So, while harvesting the biomass serves to remedy the adverse ecosystem effects on marine ecosystems (from excessive organic material, i.e. macroalgae blooms), beachcast could potentially contribute to more sustainable food production.

Sadly, it is not simple. This potentially symbiotic process infers uncertainties regarding soil cadmium accumulation, coastal ecosystem effects, and other challenges - and despite multiple studies and attempts at a waste-to-resource conversion of beachcast, the challenges remain unsolved, and a novel take on the topic seems necessary.

On Gotland, Sweden, with a historical tradition of using beachcast in agriculture, a modern governance system for management has emerged from a national policy subsidising beachcast harvesting, which has partly come to connect the marine and agricultural domains, among other actors. In this case, beachcast harvesting is subsidised as a measure to curb eutrophication and reduce the detrimental effects of excessive beachcast, a phenomenon present in the Baltic Sea and many other coastal regions worldwide that are caused by an accelerating nutrient accumulation at sea and sediment stocks. So, by further applying beachcast as a fertiliser in agriculture and horticulture, a practical example of a regional land-marine nutrient loop could be created to make beachcast management more sustainable. However, multiple challenges need to be addressed. 

This thesis and case study of Gotland, Sweden, presents an illustrative example of contemporary beachcast governance and management that provides knowledge and insights to support policy development and more sustainable beachcast management practices. insights for policy that can support the development of more sustainable management practices. This is done by using semi-structured interviews to understand the beachcast governance and management practices based on stakeholder perceptions (Paper I), performing a cost-benefit analysis of beach-cast harvest to assess the economics of closing land-marine nutrient loops in the Baltic Sea region (Paper II), conducting a cultivation experiment to predict future trends in soil cadmium concentration from applying beachcast as fertiliser (Paper III), and mapping regional variations in chemical composition of fresh and composted beachcast to consider future treatments (Paper IV). 

The results show that to overcome the challenges and achieve more sustainable practices, the following measures and considerations are essential: further supporting continued experimentation and monitoring of marine ecosystems to handle the harvest-hesitation caused by the uncertainties associated with marine ecosystem effects; sampling of composted material and careful agricultural use to remedy the waste-resource ambiguity associated with Cd contamination; and a continued subsidy and cross-sectoral collaborations to abide managerial and financial responsibility for beachcast activity.   

In this in-depth and transdisciplinary case study with a mixed-methods approach, the findings point to a theoretical and practical incongruity In seeking a waste-to-resource conversion of beachcast, which indicates that beachcast cannot compete with commercially viable products in today's intensive agricultural regime. Instead, agroecology, an alternative pathway according to FAO, appears to be a more promising context for beachcast to be acknowledged and receive the necessary investment to resolve its ambiguous resource status. 

Abstract [sv]

Släke, det Gotländska samlingsnamnet för uppspolad alg- och tångmassa, brukade vara en mycket eftertraktad jordbruksresurs (gödselmedel och markvårdare) i kustsamhällen runt om i hela världen innan kemiska gödningsmedel introducerades i jordbruket, men med tanke på hållbarhetsmål som inbegriper konceptet cirkulär bio-ekonomi borde vi kanske återinföra släke som resurs?

Sedan släkeanvändningen övergavs inom jordbruket har mängden släke ökat avsevärt (som en effekt av övergödningen till följd av användningen av kemiska gödningsmedel) och materialet betraktas vanligtvis som avfall. Samtidigt degraderas många jordar till följd av minskad tillförsel av organiskt material, något som släke skulle kunna bidra med till agroekologiska system. Så bortforsling av släke från lämpliga kustremsor skulle teoretiskt sett både kunna avhjälpa de negativa effekterna på marina ekosystem från makroalgblomning (som en följd av övergödningen) samt bidra till en mer hållbar livsmedelsproduktion genom näringscirkulation.

Tyvärr är det i praktiken inte en enkel uppgift att åstadkomma ett sådant cirkulärt resurssystem för släke. Denna till synes symbiotiska process är förknippad med osäkerheter vad gäller kadmiumackumulering i jord, potentiellt negativa effekter på kustnära ekosystem och andra utmaningar - så trots flera studier och försök till en omvandling av släke från avfall till resurs, kvarstår utmaningen med resursomvandlingen och det finns ett behov av ett nytt angreppssätt på släke-problematiken.

På Gotland, Sverige, med en historisk tradition av att använda släke i jordbruket, har ett modernt resurshanteringssystem vuxit fram ur en nationell policy som subventionerar släkeskörd som en övergödningsåtgärd. Systemet har kommit att engagera flertalet olika aktörer och har delvis kopplat samman marina och agrara domän. I det här fallet subventioneras alltså släkeskörd som en åtgärd för att bromsa övergödning och minska de skadliga effekterna makroalgsblomningar, ett fenomen som återfinns i Östersjön och många andra kustområden över hela världen som orsakas av en accelererande ackumulering av näringsämnen i havet, inklusive sediment. Så genom att ytterligare använda släke som gödningsmedel i jordbruk och trädgårdsodling, skulle näringscirkulation mellan hav och land i praktiken kunna skapas på regional skala för att göra släkehanteringen mer hållbar, även om flera utmaningar måste lösas. 

Denna avhandling och fallstudie av släkeskörd på Gotland, Sverige är ett illustrativt exempel på samtida släkehantering som ger kunskap och insikter till användning för policy som kan stödja utvecklingen av mer hållbar hantering. Detta görs genom semi-strukturerade intervjuer för att förstå släkehanteringen utifrån olika aktörers uppfattningar (Paper I), kostnads-nyttoanalys av släkeskörd och bortforsling för en samhällsekonomisk bedömning av ett kretslopp av släke mellan hav och land i Östersjöregionen (Paper II), odlingsexperiment för att förutsäga framtida trender av kadmiumkoncentration i jord från användning av släke som gödningsmedel (Paper III), samt kartläggning av regionala variationer i kemisk sammansättning av färsk och komposterad släke för att betänka framtida behandlingsmetoder (Paper IV).

För att klara av utmaningarna och uppnå mer hållbara metoder visar resultaten av avhandlingen att följande åtgärder och överväganden viktiga: att ytterligare stödja en fortsatt experimentering och övervakning av marina ekosystem för att hantera osäkerheterna kring de marina ekosystemeffekterna; kontinuerlig provtagning av komposterad släke och försiktig jordbruksanvändning för att råda bot på avfalls-resurs-ambivalensen som är förknippad med en potentiell Cd-kontaminering, samt en fortsatt subventionering och upprätthållande av tvärsektoriella samarbeten för ett delat ansvarstagande (också ekonomiskt) för släkehanteringen.

I denna djupgående och transdisciplinära fallstudie pekar resultaten på en teoretisk och praktisk inkongruens när det kommer till omvandlingen från avfall till resurs av släke. I sin tur är det en indikation på att släke inte kan konkurrera med kommersiellt gångbara produkter i dagens intensiva jordbruksregim. Istället verkar agroekologi, en alternativ väg till intensifiering enligt FAO, vara ett mer lovande sammanhang för att släke ska komma till sin rätt och få till de nödvändiga investeringar som krävs för att lösa dess tvetydiga resursstatus. 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2023. , p. 109
Series
TRITA-ABE-DLT ; 2347
Keywords [en]
Beachcast, natural resource management, policy, circular bio-economy, agroecosystems, governance, sustainable development, industrial ecology
Keywords [sv]
Släke, naturresursteknik, policy, cirkulär bioekonomi, agroekologiska system, naturresursförvaltning, hållbar utveckling, industriell ekologi i
National Category
Other Environmental Engineering
Research subject
Industrial Ecology
Identifiers
URN: urn:nbn:se:kth:diva-339418ISBN: 978-91-8040-766-3 (print)OAI: oai:DiVA.org:kth-339418DiVA, id: diva2:1810838
Public defence
2023-12-01, F3, Lindstedtsvägen 26, KTH Campus, public video conference link https://kth-se.zoom.us/j/62886879434, 114 28 Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20231110

Available from: 2023-11-10 Created: 2023-11-09 Last updated: 2023-11-27Bibliographically approved
List of papers
1. Using stakeholder perceptions to deepen the understanding of beachcast governance and management practices on Gotland, Sweden
Open this publication in new window or tab >>Using stakeholder perceptions to deepen the understanding of beachcast governance and management practices on Gotland, Sweden
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2023 (English)In: Ocean and Coastal Management, ISSN 0964-5691, E-ISSN 1873-524X, Vol. 239, article id 106583Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
Elsevier BV, 2023
National Category
Health Sciences
Identifiers
urn:nbn:se:kth:diva-326876 (URN)10.1016/j.ocecoaman.2023.106583 (DOI)000968662300001 ()2-s2.0-85151027595 (Scopus ID)
Note

QC 20230515

Available from: 2023-05-15 Created: 2023-05-15 Last updated: 2023-11-09Bibliographically approved
2. Cost–benefit analysis of beach-cast harvest: Closing land-marine nutrient loops in the Baltic Sea region
Open this publication in new window or tab >>Cost–benefit analysis of beach-cast harvest: Closing land-marine nutrient loops in the Baltic Sea region
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2022 (English)In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 51, no 5, p. 1302-1313Article in journal (Refereed) Published
Abstract [en]

Harvesting beach-cast can help mitigate marine eutrophication by closing land-marine nutrient loops and provide a blue biomass raw material for the bioeconomy. Cost–benefit analysis was applied to harvest activities during 2009–2018 on the island of Gotland in the Baltic Sea, highlighting benefits such as nutrient removal from the marine system and improved recreational opportunities as well as costs of using inputs necessary for harvest. The results indicate that the activities entailed a net gain to society, lending substance to continued funding for harvests on Gotland and assessments of upscaling of harvest activities to other areas in Sweden and elsewhere. The lessons learnt from the considerable harvest experience on Gotland should be utilized for developing concrete guidelines for carrying out sustainable harvest practice, paying due attention to local conditions but also to what can be generalized to a wider national and international context.

Place, publisher, year, edition, pages
Springer Nature, 2022
Keywords
Beach recreation, Beach wrack, Bioeconomy, Circular economy, Eutrophication, Nutrient loops, biomass, cost-benefit analysis, marine environment, pollutant removal, spatiotemporal analysis, Atlantic Ocean, Baltic Sea, Gotland, Sweden, nitrogen, Baltic States, cost benefit analysis, Nutrients
National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-313251 (URN)10.1007/s13280-021-01641-8 (DOI)000719717500001 ()34787831 (PubMedID)2-s2.0-85119203226 (Scopus ID)
Note

QC 20220613

Available from: 2022-06-13 Created: 2022-06-13 Last updated: 2023-11-09Bibliographically approved
3. Cd accumulation in soil from beachcast application: A long-term prediction of its reintroduction for bio-fertilisation in Gotland, Sweden
Open this publication in new window or tab >>Cd accumulation in soil from beachcast application: A long-term prediction of its reintroduction for bio-fertilisation in Gotland, Sweden
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The ecological consequences of using beachcast compost as an agricultural resource input merit study. Using beachcast compost as a biofertiliser has multiple positive effects on agroecosystems, while also serving to remedy the negative effects on marine ecosystems caused by excessive beachcast production due to eutrophication. This process thus presents an opportunity to contribute to circular nutrient management and the development of sustainable agricultural, but it may also result in accumulation Cd (Cd) in the soil. In Gotland, Sweden, an example of cross-scale interaction between marine and agricultural domains has emerged from a national policy subsidising beachcast harvesting, which may help reintroduce the historical tradition of using beachcast in agriculture. To estimate potential risks, a field experiment and Cd mass balance were conducted to predict the rate of Cd accumulation, changes in soil Cd fractions, and potential beachcast application methods that avoid Cd soil accumulation. In the scenario where the maximum Cd input from beachcast compost is set to the same threshold as the level established for sewage sludge—0.75 g ha–1 year–1—beachcast compost with a Cd content of 1.5 mg kg–1 dw (the EU threshold for biofertilisers) could be applied in an amount of approximately 2000 kg ha–1 per year (one-tenth of the amount applied in this study). Therefore, the long-term effects of Cd soil accumulation resulting from continuous application of beachcast as fertiliser on agroecosystems cannot be disregarded and are of global relevance. 

 

Keywords
beachcast, biofertiliser, soil, cadmium, accumulation modelling
National Category
Soil Science
Identifiers
urn:nbn:se:kth:diva-339416 (URN)
Note

QC 20231110

Available from: 2023-11-09 Created: 2023-11-09 Last updated: 2023-11-10Bibliographically approved
4. Regional variations in the chemical composition of fresh and composted beachcast on the island of Gotland, Sweden – considering future treatments
Open this publication in new window or tab >>Regional variations in the chemical composition of fresh and composted beachcast on the island of Gotland, Sweden – considering future treatments
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Harvesting beachcast from coastal zones to use the biomass in agriculture or horticulture could mitigate eutrophication while contributing to resource substitution of fossil-based inputs in food production. As such, beachcast holds great resource potential in a bio-based circular economy, but its chemical properties prove challenging, and more research is required to develop treatment techniques that will allow the realisation of such a system. We compiled results from chemical analyses of fresh beachcast from a database within the marine policy scheme, LOVA, in Gotland, Sweden, to study local and seasonal variations in macronutrients, C:N ratio, and Cd content. This data complemented with analyses of fresh and composted beachcast (passive pile treatment), for which the contents of macronutrient, ammonium, nitrate, and Cd, were measured, calculating C:N ratios and maturity indices (NH4+-N/NO3—N). The results confirm that regional variations in the above-mentioned properties require investments in treatment techniques and strategies to make beachcast usable. 

Keywords
beachcast, chemical composition, treatment, waste-to-resource conversion, sustainable resource management
National Category
Other Natural Sciences Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-339417 (URN)
Note

QC 20231110

Available from: 2023-11-09 Created: 2023-11-09 Last updated: 2023-11-10Bibliographically approved

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