Combatting eutrophication is currently a major challenge for policy makers in the Baltic Sea region, and it is likely to remain so in the decades to come. Although total nutrient loads to the Baltic Sea have recently declined, the gap between current loadings and those required to ensure the desired status is still substantial (Reusch et al. 2018). This Special Issue is dedicated to research that helps inform how the eutrophication challenge might best be addressed by improving our understanding of technological constraints, societal drivers of change, land uses, environmental policies, and innovative governance with stakeholder involvement. These issues are important for the current generation and those to come and are issues we must address in order to succeed in reducing nutrient loads to the desired levels to gradually achieve the desired good environmental status of the Baltic Sea. Currently, we witness a new era of water policies across the entire Baltic Sea region. Our changing climate is impacting on precipitation and runoff, and is also the reason why new EU climate policies seek to tie carbon sinks more visibly to carbon sources. Both these aspects have repercussions for water policies. Thus, solving eutrophication challenges requires sharpening of existing policies and instruments, as well as creating new insights and governance approaches with broad stakeholder involvement in a changing environment. In order to design coherent water and climate policies, and target and implement those policies more efficiently, policy makers need to combine new insights regarding the inhabitants in the region, the catchments, and the Baltic Sea itself. Such insights can be expected from soil scientists, agronomists, hydrogeologists, marine ecologists, economists, and social and policy scientists. What is needed is on the one hand effectively targeted governance at appropriate spatial and temporal scales, adapted to differing interests and motivations of citizens living around the Baltic Sea, and on the other hand fine tuning and co-designing of policies at local, national, Baltic Sea regional and EU level. This Special Issue brings together recent research from four BONUS-funded projects—BONUS BALTICAPP, BONUS GO4BALTIC, BONUS MIRACLE and BONUS SOILS2SEA—that comprised part of the ‘Viable Ecosystem’ and ‘Sustainable Ecosystem Services’ BONUS research programmes. The projects addressed these common concerns through somewhat different, but inter-related, themes. Key messages emphasized and discussed in the research papers of this Special Issue are summarized under four interlinked themes: Scenarios for the future, Policies and ecosystem services in water governance, Novel approaches for managing nutrients, and Advanced modelling from field level to the entire Baltic Sea region.

With growing urbanization cities become hotspots for nutrients. Food items are imported, and food residues, including excreta and not-eaten food, are often exported to landfill sites and water bodies. However, urban sanitation systems can be designed to achieve a high degree of nutrient recovery and food security while counteracting current nutrient resources depletion, environmental degradation, and wasteful energy use. This article illustrates how an extended solid waste hierarchy also including human excreta and wastewater can guide actions to save and recover phosphorus (P) by the three sectors: food industry, households, and waste utilities. P use in diets and agricultural production is not part of the analysis, despite the potential to save P. Novel systems thinking and material flow analysis show that waste prevention can replace over 40% of mined P presently used for making fertilizers. Reuse and recycling of P in excreta and food waste can replace another 15–30%, depending on P efficiency from mine to plate. Keeping excreta separated from other wastewater facilitates such measure. Incineration and land filling are deemed the least appropriate measures since mainly P is recovered in the ashes. The European Union (EU) waste management policy is analyzed for real barriers and opportunities for this approach. The EU Parliament policy guidelines were watered down in the EU Commission’s Directives, and today most biowastes are still being landfilled or incinerated instead of recovered. An anticipated overcapacity of incineration plants in Europe threatens to attract all combustible materials and therefore, irrevocably, reduce nutrient recovery. On the other hand, reduced generation and enhanced recovery can delay exhaustion of P resources by several centuries and simultaneously reduce environmental degradation.

As part of efforts to reduce the eutrophying load to Lake Victoria, a wastewater treatment system at one of the sugar factories in Kenya was evaluated with the ecosystem ecology method emergy accounting. As a comparison a traditional cost analysis was also performed. The analysis included the local and imported ecosystem services. After preliminary treatment the effluent was discharged into a series of 12 stabilisation ponds. The removal of COD and TSS was high, whereas phosphorus concentrations were reduced by less than 20 %. The monetary costs were dominated by operation and management cost, some of which could probably be reduced by more effective management. The local ecosystem services in emergy terms contributed only 1% (or 1,000 Em$) to the treatment system. Imported ecosystem services in purchased lime contributed more to the treatment system, 22% (or 24,600 Em$). Since the land costs in the area were low, land demanding treatment methods using free local ecosystem services, could be cost effective choices for wastewater management. Ecosystem ecology methods as emergy accountings can guide these choices by revealing the additional contribution of free ecosystem services. Emergy accountings seem to need further clarification regarding differences in micro-/macroeconomic views.

Raising environmental awareness among farmers is the key to successfully reaching environmental goals. The present study assessed the knowledge development process and the raising of environmental awareness among 30 farmers from Poland exposed to four approaches aimed to reduce phosphorus (P) and nitrogen (N) losses to water. The farmers were interviewed with open-ended questions on-farm both before and after the project intervention. As hoped, the farmers attempted to adjust their farm practices to the European Union regulations, which are in some cases supported by subsidies. As a complement, the project offered tools for system-thinking based on farm data and support from agricultural advisors: a) a survey of plant-available P, potassium (K), magnesium (Mg), and soil pH, resulting in soil maps; b) assessment of nitrogen leaching risks from individual fields; c) compilation of a farm-gate balance. Farmers were positive to soil surveys and maps, but had limited understanding of the nutrient balance concept and calculations. They generally relied on their own experiences regarding fertilization rather than on calculated farm nutrient balances and leaching risks. Farmers’ understanding and willingness to adopt new approaches to improve nutrient efficiency and reduce negative environmental impacts are discussed.

Data from seven constructed wetlands (CWs) in the south of Sweden were analyzed to investigate the effects of water flow and season on inflow phosphorus (P) concentrations and temporal P retention variations in CWs receiving runoff from arable land. The form of P (dissolved or particulate) during different water flows (high and low) and seasons (warm and cold) was investigated using the results of total P (TP) and phosphate analyzed in grab samples that had been collected regularly or occasionally during two to nine years, along with continuous water flow measurements.

The form of inflow and outflow P (particulate or dissolved P) differed between CWs, and also varied with season and flow. For instance, in three of the CWs, particulate P (PP) dominated the inflow during the cold period with high flow, while during the other periods the proportion of PP was approximately 50%. In one CW situated in a catchment with high clay content, PP dominated both inflow and outflow at all times. The average clay content in catchment top soils was positively correlated to the flow-weighted inflow TP concentrations.

In three CWs receiving runoff through drainage pipes, the relationship between TP concentrations (TP_in) and water flow was positive, both during high and low flow, and during warm and cold period. However, in four CWs that received surface water runoff, the relationship between TP_in and water flow was positive during high flow periods (i.e. the 25% sampling occasions with the highest flow), and during low flow and warm period, the relationship was negative in these four wetlands, indicating either anoxic stagnant water upstream or influence from rural wastewater.

The temporal dynamics of P concentrations mean that in some of the CWs, the main part of the annual P retention may occur during a few days with high water flows. The correlation between concentration and water flow suggests that the water sampling strategy may have a considerable impact on retention estimates, as exemplified by some calculation examples.

This study analysed variations in sediment deposition and accumulation to improve understanding of retention processes in small wetlands constructed on clay soils. Sediment deposition (in traps) and accumulation (on plates) was measured in four wetlands in east-central Sweden.

Particle deposition generally exceeded (up to eight-fold) the total particle load to the wetlands, especially in the spring-summer period, suggesting that the settled particles in the traps were generated from internal processes. The particles probably originated from erosion of the bottom and sides of the wetlands, or from production of organic material which deposited in the traps.

Particle resuspension was evident in all wetlands and considered an important process. Only 13-23% of the deposited material in the traps remained on the plates in the wetlands. Both particle deposition and accumulation was very low in one wetland receiving high hydraulic load (HL, 400 m yr-1), suggesting that such high-loaded wetlands are not efficient as particle sinks in clay soil areas. In the other wetlands, more than 80% of the total sediment accumulation occurred in the initial parts of the wetlands (which represented the first 20% of the total wetland area), indicating the importance of designing wetlands with an initial wetland section that is easy accessed for sediment removal as maintenance.

The results from this study point to the importance of internal processes and resuspension for annual particle accumulation in constructed wetlands.

Biogas Research Center (BRC) är ett kompetenscentrum för biogasforskning som finansieras av Energimyndigheten, LiU och ett flertal externa organisationer med en tredjedel vardera. BRC har en mycket bred tvärvetenskaplig inriktning och sammanför biogasrelaterad kompetens från flera olika områden för att skapa interaktion på flera olika plan:

• mellan näringsliv, akademi och samhälle,
• mellan olika perspektiv, samt
• mellan olika discipliner och kompetensområden.

BRC:s vision är:

Resurseffektiva biogaslösningar finns genomförda i många nya tillämpningar och bidrar till en mer hållbar energiförsörjning, förbättrat miljötillstånd och goda affärer.

BRC:s särskilda roll för att uppnå denna vision är att bidra med kunskapsförsörjning och process-/teknikutveckling för att facilitera utveckling, innovation och implementering av biogaslösningar. Resurseffektivitet är ett nyckelord, vilket handlar om att förbättra befintliga processer och system samt utveckla biogaslösningar i nya sektorer och möjliggöra användning av nya substrat.

For BRC:s etapp 1, den första tvåårsperioden mellan 2012-2014, var forskningsprojekten organiserade enligt tabellen nedan. Den visar viktiga utmaningar för biogasproducenter och andra intressenter, samt hur dessa ”angreps” med åtta forskningsprojekt. Fem av projekten var av explorativ karaktär i bemärkelsen att de var bredare och mer framtidsorienterade - exempelvis utvärderade flera möjliga tekniska utvecklingsmöjligheter (EP1-5). Tre projekt hade ett tydligare fokus på teknik- och processutveckling (DP6-8).

I den här slutrapporten ges en kortfattad bakgrundsbeskrivning och det finns en introduktion till vad den här typen av kompetenscentrum innebär generellt. Därefter finns mer detaljerad information om BRC, exempelvis gäller det centrumets etablering, relevans, vision, hörnstenar och utveckling. De deltagande organisationerna presenteras, både forskargrupperna vid Linköpings universitet och partners och medlemmar. Vidare finns en mer utförlig introduktion till och beskrivning av utmaningarna i tabellen och kortfattat information om forskningsprojekten, följt av ett kapitel som berör måluppfyllelse och den externa utvärdering som gjorts av BRC:s verksamhet. Detaljerad, listad information finns till stor del i bilagorna.

Kortfattat kan det konstateras att måluppfyllelsen överlag är god. Det är speciellt positivt att så många vetenskapliga artiklar publicerats (eller är på gång att publiceras) kopplat till forskningsprojekten och även i det vidare centrumperspektivet. Helt klart förekommer en omfattande verksamhet inom och kopplat till BRC. I etapp 2 är det viktigt att öka andelen mycket nöjda partner och medlemmar, där nu hälften är nöjda och hälften mycket nöjda. Det handlar framför allt om stärkt kommunikation, interaktion och projektledning. Under 2015 förväntas åtminstone två doktorsexamina, där avhandlingarna har stor koppling till forskningen inom etapp 1.

I början på år 2014 skedde en extern utvärdering av verksamheten vid BRC med huvudsyftet att bedöma hur väl centrumet lyckats med etableringen samt att granska om det fanns förutsättningar för framtida framgångsrik verksamhet. Generellt var utfallet mycket positivt och utvärderarna konstaterade att BRC på kort tid lyckats etablera en verksamhet som fungerar väl och engagerar det stora flertalet deltagande aktörer, inom relevanta områden och där de flesta involverade ser BRC som en befogad och väl fungerande satsning, som de har för avsikt att även fortsättningsvis stödja. Utvärderingen bidrog också med flera relevant tips och till att belysa utmaningar.

Utöver denna slutrapport finns separata publikationer från forskningsprojekten.

Arbetet som presenteras i rapporten har finansierats av Energimyndigheten och de medverkande organisationerna.

Biogas Research Center (BRC) is a center of excellence in biogas research funded by the Swedish Energy Agency, Linköping University and a number of external organizations with one-third each. BRC has a very broad interdisciplinary approach, bringing together biogas-related skills from several areas to create interaction on many levels:

• between industry, academia and society,
• between different perspectives, and
• between different disciplines and areas of expertise.

BRC’s vision is:

BRC contributes to the vision by advancing knowledge and technical development, as well as by facilitating development, innovation and business. Resource efficiency is central, improving existing processes and systems as well as establishing biogas solutions in new sectors and enabling use of new substrates.

For BRC phase 1, the first two year period from 2012-2014, the research projects were organized in accordance with the table below showing important challenges for biogas producers and other stakeholders, and how these challenges were tackled in eight research projects. Five of the projects had an exploratory nature, meaning that they were broader, more future oriented and, for example, evaluated several different technology paths (EP1-5). Three projects focused more on technology and process development (DP6-8).

This final report briefly presents the background and contains some information about competence centers in general. Thereafter follows more detailed information about BRC, for example, regarding the establishment, relevance, organization, vision, corner stones and development. The participating organizations are presented, both the research groups within Linköping University and the partners and members. Further on, there is a more detailed introduction to and description of the challenges mentioned in the table above and a short presentation from each of the research projects, followed by some sections dealing with fulfillment of objectives and an external assessment of BRC. Detailed, listed information is commonly provided in the appendices.

Briefly, the fulfillment of objectives is good and it is very positive that so many scientific articles have been published (or are to be published) from the research projects and also within the wider center perspective. Clearly, extensive and relevant activities are ongoing within and around BRC. In phase 2 it essential to increase the share of very satisfied partners and members, where now half of them are satisfied and the other half is very satisfied. For this purpose, improved communication, interaction and project management are central. During 2015, at least two PhD theses are expected, to a large extent based on the research from BRC phase 1.

In the beginning of 2014 an external assessment of BRC was carried out, with the main purpose to assess how well the center has been established and to review the conditions for a future, successful competence center. Generally, the outcome was very positive and the assessors concluded that BRC within a short period of time had been able to establish a well-functioning organization engaging a large share of the participants within relevant areas, and that most of the involved actors look upon BRC as a justifiable and well working investment that they plan to continue to support. The assessment also contributed with several relevant tips of improvements and to clarify challenges to address.

This report is written in Swedish, but for each research project there will be reports and/or scientific papers published in English.

The work presented in this report has been financed by the Swedish Energy Agency and the participating organizations.

In water management, source areas need to be identified and seasonal variability of nutrient flows assessed to facilitate design of cost-efficient mitigation programs. This study aimed at investigating to what degree sub-catchment spatial and temporal nutrient concentration variability could be captured by their agro-geographical characteristics and water quality modelling.

An agricultural catchment (160 km2) in Southeast Sweden was investigated with respect to source areas for phosphorus (P), nitrogen and particle losses. The specific aims were to 1) investigate the spatial variability of nutrient and particle concentrations and transport from different sub-catchments, 2) analyze if sub-catchment characteristics could explain differences in nutrient and particle concentration dynamics and overall nutrient losses, and 3) evaluate how well monitored temporal and spatial variability in nutrient concentrations could be simulated by a catchment model (HYPE). The purpose with the latter was to find recommendations for further model development and identify limitations for the use of catchment models in local water management.

Water flow was measured in two stations during 2009-2011. Grab samples were collected in synoptic sampling campaigns covering 10 sampling points during periods that represented various water flow regimes. Water samples were analyzed for total P (TP), dissolved phosphate (PO4-P), nitrate (NO3-N) and suspended matter (SUSP). The HYPE model was setup with the same detailed agro-geographical data as used for the statistical analyses of spatial and temporal correlations. The results showed that the sub-catchment variability of all measured nutrient concentrations were correlated with agro-geographical characteristics. All fractions of P concentrations were strongly correlated with soil type, whereas NO3-N concentrations were more related to crop factors. With regard to temporal dynamics of monitored concentrations, links to seasonality and water flow were more significant for NO3-N than for TP. Concentrations generated from the water quality model (HYPE) did not capture the subcatchment or temporal variability indicated from monitoring, particularly not for P concentrations. Neither did the modelled correlation between agro-geographical factors and concentrations correspond to that found for monitored concentrations. Some suggestions for model improvement were identified. Although water quality models are useful for local water management when it comes to modelling the impact of e.g. measures or climate change, our results suggest that their value might still be more limited when assessing variability on the subcatchment scale.

As global consumption expands, the world is increasingly facing threats to resource availability and food security. To meet future food demands, agricultural resource efficiency needs to be optimized for both water and nutrients. Policy makers should start to radically rethink nutrient management across the entire food chain. Closing the food loop by recycling nutrients in food waste and excreta is an important way of limiting the use of mineral nutrients, as well as improving national and global food security. This article presents a framework for sustainable nutrient management and discusses the responsibility of four key stakeholder groups—agriculture, the food industry, consumers, and waste management—for achieving an effective food loop. In particular, we suggest a number of criteria, policy actions, and supporting strategies based on a cross-sectoral application of the waste hierarchy.

The series of papers in this issue of AMBIO represent technical presentations made at the 7th International Phosphorus Workshop (IPW7), held in September, 2013 in Uppsala, Sweden. At that meeting, the 150 delegates were involved in round table discussions on major, predetermined themes facing the management of agricultural phosphorus (P) for optimum production goals with minimal water quality impairment. The six themes were (1) P management in a changing world; (2) transport pathways of P from soil to water; (3) monitoring, modeling, and communication; (4) importance of manure and agricultural production systems for P management; (5) identification of appropriate mitigation measures for reduction of P loss; and (6) implementation of mitigation strategies to reduce P loss. This paper details the major challenges and research needs that were identified for each theme and identifies a future roadmap for catchment management that cost-effectively minimizes P loss from agricultural activities.