Efforts are on the way on the Swedish West Coast to develop the capacity for cultivation of marine resources, notably of kelps. Given that this is a region of great natural and national heritage, public opposition to marine developments has been identified as a possible risk factor. This survey thus sought to shed light on awareness levels, perceptions of different types of aquaculture and on reactions to a scenario depicting future aquaculture developments on the West Coast. When asked about their general opinions of aquaculture, respondents tended to be favourable though a majority chose neutral responses. On the whole, respondents were favourable to the depicted scenario. Finally, it was found that the high-awareness group tended to be more supportive than the low or medium-awareness groups, hinting at the benefits of increasing awareness to reduce public aversion and to support a sustainable development of aquaculture on the Swedish West Coast.

Eutrophication is one of the most serious global threats to coastal areas. One effect of eutrophication is seasonal macroalgal blooms. As a consequence, large amounts of beach-cast algae are today reported from coastal areas worldwide. In this study, we analyze nonmarket benefits by capturing local residents’ Willingness To Pay (WTP) for an environmental program to regularly remove and utilize beach-cast algae to produce bioenergy and biofertilizer. Results indicate a considerable WTP among local residents in the Baltic Sea study site. This WTP estimate together with a potential increase in non-resident beach tourism amounts to potentially substantial welfare benefits from the environmental program. These benefits could encourage similar environmental programs in the future.

Today, concerns prevail about the unsustainable use of phosphorus and worldwide eutrophication, thus requiring efficient management of phosphorus flows. With increasing population and associated urban growth, urban management of phosphorus flows in the perspectives of recycling, eutrophication and total budget becomes increasingly important. This study mapped phosphorus flows for a reference year (2013) and a future year (2030) using different scenarios for the city of Stockholm, Sweden. The results indicated that the Swedish goal of recycling phosphorus from wastewater would cover the majority of the total phosphorus budget for Stockholm. However, in 2013, only 10% of phosphorus was recycled for agricultural use, around half of which was from sewage sludge and the other half from food waste. Almost 50% of total phosphorus was sent to landfill/mining waste capping with sewage sludge, for economic reasons and lack of market. Among the scenarios of upstream and downstream urban management options studied in combination with population growth, recovery of phosphorus from sewage sludge had the greatest potential to increase the fraction recycled to agriculture. However, only upstream measures, e.g. changed diet, were able to reduce the total phosphorus budget. Urban management of phosphorus flows based on the different perspectives of recycling, eutrophication or total budget was shown to potentially result in different preferred management actions and both upstream and downstream measures need to be considered. Moreover, management needs to pay attention to small but environmentally sensitive flows, particularly when setting city goals on phosphorus recycling by percentage in a large budget.

The cultivation of seaweed as a feedstock for third generation biofuels is gathering interest in Europe, however, many questions remain unanswered in practise, notably regarding scales of operation, energy returns on investment (EROI) and greenhouse gas (GHG) emissions, all of which are crucial to determine commercial viability. This study performed an energy and GHG emissions analysis, using EROI and GHG savings potential respectively, as indicators of commercial viability for two systems: the Swedish Seafarm project's seaweed cultivation (0.5 ha), biogas and fertilizer biorefinery, and an estimation of the same system scaled up and adjusted to a cultivation of 10 ha. Based on a conservative estimate of biogas yield, neither the 0.5 ha case nor the up-scaled 10 ha estimates met the (commercial viability) target EROI of 3, nor the European Union Renewable Energy Directive GHG savings target of 60% for biofuels, however the potential for commercial viability was substantially improved by scaling up operations: GHG emissions and energy demand, per unit of biogas, was almost halved by scaling operations up by a factor of twenty, thereby approaching the EROI and GHG savings targets set, under beneficial biogas production conditions. Further analysis identified processes whose optimisations would have a large impact on energy use and emissions (such as anaerobic digestion) as well as others embodying potential for further economies of scale (such as harvesting), both of which would be of interest for future developments of kelp to biogas and fertilizer biorefineries.

Managing nutrient flows to urban lakes is one of the main challenges to environmental sustainability in cities. Considering that future urban and climate changes may increase the challenge of handling future eutrophication, prediction of future nutrient loadings to aquatic environments in urban catchments has become increasingly important. Based on a new, innovative, structured Substance Flow Analysis (SFA) approach, where a source model was coupled to a Generalised Watershed Loading Functions (GWLF) model, this study investigated nutrient (nitrogen and phosphorus) delivery from sources to a water recipient for an urban catchment, using the case of Racksta Trask in Stockholm, Sweden, as an example. Potential effects from future changes in atmospheric deposition, vehicle volume and land use and from climate change (temperature and precipitation) were examined by comparing model scenarios in two periods (2000-2009 and 2050-2059). Model results suggested that climate change may have a greater impact on nitrogen loading to Racksta Trask lake than increasing vehicle volume and land use change. In addition, the results suggested that nitrogen loading to the lake may increase taking into account all changes examined, despite the expected decrease in background atmospheric deposition of nitrogen. In contrast, a marginal impact was found for phosphorus loading to the lake under all scenarios examined, resulting in only a slight increase in the combined scenario. From a nutrient pathways perspective, the results suggested that major pathways of nutrient loadings to the lake may not be much affected under most future scenarios examined, although groundwater was found to be a potentially sensitive pathway of nitrogen transport in the climate scenario. The model results provided important information for managers who need to plan for future nutrient handling in urban catchments, and the coupled SFA-GWLF model was suggested to be worthy of further testing at other sites and conditions.

Anthropogenic nutrient emissions and associated eutrophication of urban lakes are a global problem. Future changes in temperature and precipitation may influence nutrient loadings in lake catchments. A coupling method, where the Generalized Watershed Loading Functions method was tested in combination with source quantification in a Substance Flow Analysis structure, was suggested to investigate diffuse nutrient sources and pathways and climate change effects on the loadings to streamflow in urban catchments. This method may, with an acceptable level of uncertainty, be applied to urban catchments for first-hand estimations of nutrient loadings in the projected future and to highlight the need for further study and monitoring. Five lake catchments in Stockholm, Sweden (Råcksta Träsk, Judarn, Trekanten, Långsjön and Laduviken) were employed as case studies and potential climate change effects were explored by comparing loading scenarios in two periods (2000-2009 and 2021-2030). For the selected cases, the dominant diffuse sources of nutrients to urban streamflow were found to be background atmospheric concentration and vehicular traffic. The major pathways of the nitrogen loading were suggested to be from both developed areas and natural areas in the control period, while phosphorus was indicated to be largely transported through surface runoff from natural areas. Furthermore, for nitrogen, a modest redistribution of loadings from surface runoff and stormwater between seasons and an increase in the annual loading were suggested for the projected future climate scenarios as compared to the control period. The model was, due to poor monitoring data availability, only able to set an upper limit to nutrient transport by groundwater both in the control period and the future scenarios. However, for nitrogen, groundwater appeared to be the pathway most sensitive to climate change, with a considerable increase and seasonal redistribution of loadings. For phosphorus, loadings by different pathways were apparently less sensitive to climate change.

Eutrophication combined with climate change has caused ephemeral filamentous macroalgae to increase and drifts of seaweed cover large areas of some Baltic Sea sites during summer. In ongoing projects, these mass occurrences of drifting filamentous macroalgae are being harvested to mitigate eutrophication, with preliminary results indicating considerable nutrient reduction potential. In the present study, an energy assessment was made of biogas production from the retrieved biomass for a Baltic Sea pilot case. Use of different indicators revealed a positive energy balance. The energy requirements corresponded to about 30%-40% of the energy content in the end products. The net energy gain was 530-800 MJ primary energy per ton wet weight of algae for small-scale and large-scale scenarios, where 6 000 and 13 000 tonnes dwt were harvested, respectively. However, the exergy efficiency differed from the energy efficiency, emphasising the importance of taking energy quality into consideration when evaluating energy systems. An uncertainty analysis indicated parametric uncertainty of about 25%-40%, which we consider to be acceptable given the generally high sensitivity of the indicators to changes in input data, allocation method, and system design. Overall, our evaluation indicated that biogas production may be a viable handling strategy for retrieved biomass, while harvesting other types of macroalgae than red filamentous species considered here may render a better energy balance due to higher methane yields.

Interest to harvest wild cyanobacteria exists due to the environmental and socioeconomic risks during cyanobacteria blooms coupled with demands for nonterrestrial-based alternatives for biofuel sources. This research, therefore, sought to estimate the wild cyanobacteria harvesting potential using Nodularia spumigena, and using the Baltic Sea as the case study. Data from literature provided during years 2003-2009 were used to perform estimations. Additional benefits of harvesting were also assessed by estimating the nutrient removal and biogas production potentials from the harvested biomass. Results indicate that one boom unit has the potential to harvest approximately 3 to 700 kg dry weight of N. spumigena per hour depending on the algae concentration of the bloom. Results also suggest that nutrient removal and biogas production potentials provide substantial additional incentives to the harvesting operation during years of extensive and highly concentrated blooms. However, during nonextensive or nonconcentrated blooms such potentials are low.

Several ongoing projects are harvesting maritime biomass from the Baltic Sea for eutrophication mitigation and utilisation of the recovered biomass. Some of this biomass comprises common reed (Phragmites australis), one of the most widespread vascular plants on Earth. Reed utilisation from eutrophied coastal areas needs to be evaluated. Therefore, a system analysis was performed of reed harvesting for biofuel and biofertiliser production. The specific objectives of the analysis were to: investigate the methane yield associated with anaerobic co-digestion of reed; make a primary energy assessment of the system; quantify Greenhouse Gas (GHG) savings when a fossil reference system is replaced; and estimate the nutrient recycling potential of the system. The results from energy and GHG calculations are highly dependent on conditions such as system boundaries, system design, allocation methods and selected indicators. Therefore a pilot project taking place in Kalmar County, Sweden, was used as a case study system. Laboratory experiments using continuously stirred tank reactor digesters indicated an increased methane yield of about 220 m(3) CH4/t volatile solids from co-digestion of reed. The energy balance for the case study system was positive, with energy requirements amounting to about 40% of the energy content in the biomethane produced and with the non-renewable energy input comprising about 50% of the total energy requirements of the system. The net energy value proved to be equivalent to about 40 L of petrol/t reed wet weight. The potential to save GHG emissions compared with a fossil reference system was considerable (about 80%). Furthermore an estimated 60% of the nitrogen and almost all the phosphorus in the biomass could be re-circulated to arable land as biofertiliser. Considering the combined benefits from all factors investigated in this study, harvesting of common reed from coastal zones has the potential to be beneficial, assuming an appropriate system design, and is worthy of further investigations regarding other sustainability aspects.

Nutrient loads to aquatic recipients can be expected to change due to climate change. In this work, we focus on nitrogen loads to the lake Råcksta Träsk in Stockholm, Sweden as an example of an urban ecosystem. A substance flow model is developed to describe the sources and pathways of nitrogen at present. A feed-back table approach is applied to indicate potential climate change effects on nitrogen source strengths and processes in pathways, using existing regional climate change scenarios. The tentative results indicate that biological, hydrological, meteorological and biogeochemical effects and change in human behavior as response to climate change may lead to altered nitrogen flows through an urban catchment.