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Sewage sludge contains significant amounts of resources, such as nutrients and organic matter. At the same time, the organic contaminants (OC) found in sewage sludge are of growing concern. Consequently, in many European countries incineration is currently favored over recycling in agriculture. This study presents a Multi-Attribute Value Theory (MAVT)-based decision support tool (DST) for facilitating sludge treatment decisions. Essential decision criteria were recognized and prioritized, i.e., weighted, by experts from water utilities. Since the fate of organic contaminants was in focus, a simple scoring method was developed to take into account their environmental risks. The final DST assigns each sludge treatment method a preference score expressing its superiority compared to alternative methods. The DST was validated by testing it with data from two Finnish municipal wastewater treatment plants (WWTP). The validation results of the first case study preferred sludge pyrolysis (preference score: 0.629) to other alternatives: composting and incineration (score 0.580, and 0.484 respectively). The preference scores were influenced by WWTP dependent factors, i.e., the operating environment and the weighting of the criteria. A lack of data emerged as the main practical limitation. Therefore, not all of the relevant criteria could be included in the value tree. More data are needed on the effects of treatment methods on the availability of nutrients, the quality of organic matter and sludge-borne OCs. Despite these shortcomings, the DST proved useful and adaptable in decision-making. It can also help achieve a more transparent, understandable and comprehensive decision-making process. [ABSTRACT FROM AUTHOR]

Following changes over recent years in fertilizer legislative framework throughout Europe, phosphorus (P) is taking over the role of being the limiting factor in fertilizer application rate of animal manure. This results in less placement area for spreading animal manure. As a consequence, more expensive and energy demanding synthetic fertilizers are required to meet crop nutrient requirements despite existing manure surpluses. Anaerobic digestion followed by mechanical separation of raw digestate, results in liquid fraction (LF) of digestate, a product poor in P but rich in nitrogen (N) and potassium (K). A 3-year field experiment was conducted to evaluate the impact of using the LF of digestate as a (partial) substitute for synthetic N fertilizer. Two different fertilization strategies, the LF of digestate in combination with respectively animal manure and digestate, were compared to the conventional fertilization regime of raw animal manure with synthetic fertilizers. Results from the 3-year trial indicate that the LF of digestate may substitute synthetic N fertilizers without crop yield losses. Through fertilizer use efficiency assessment it was observed that under-fertilization of soils with a high P status could reduce P availability and consequently the potential for P leaching. Under conditions of lower K application, more sodium was taken up by the crop. In arid regions, this effect might reduce the potential risk of salt accumulation that is associated with organic fertilizer application. Finally, economic and ecological benefits were found to be higher when LF of digestate was used as a synthetic N substitute. Future perspectives indicate that nutrient variability in bio-based fertilizers will be one of the greatest challenges to address in the future utilization of these products. [ABSTRACT FROM AUTHOR]

During leaf senescence resources are managed, with nutrients mobilized from older leaves to new sink tissues. The latter implies a dilemma in terms of resource utilization, the leaf senescence should increase seed quality whereas delay in senescence should improve the seed yield. Increased knowledge about nutrient recycling during leaf senescence could lead to advances in agriculture and improved seed quality. Macromolecules mobilized during leaf senescence include proteins and nucleic acids. Although nucleic acids have been less well studied than protein degradation, they are possible reservoirs of nitrogen and phosphorous. The present study investigated nuclease activities and gene expression patterns of five members of the S1/P1 family in French bean ( Phaseolus vulgaris L. cv.)Page: 2 during leaf senescence. An in-gel assay was used to detect nuclease activity during natural and dark-induced senescence, with single-stranded DNA (ssDNA) used as a substrate. The results revealed two nucleases (glycoproteins), with molecular masses of 34 and 39 kDa in the senescent leaves. The nuclease activities were higher at a neutral than at an acidic pH. EDTA treatment inhibited the activities of the nucleases, and the addition of zinc resulted in the recovery of these activities. Both the 34 and 39 kDa nucleases were able to use RNA and double-stranded DNA (dsDNA) as substrates, although their activities were low when dsDNA was used as a substrate. In addition, two ribonucleases with molecular masses of 14 and 16 kDa, both of which could only utilize RNA as a substrate, were detected in the senescent leaves. Two members of the S1/P1 family, PVN2 and PVN5 , were expressed under the experimental conditions, suggesting that these two genes were involved in senescence. The nuclease activity of the glycoproteins and gene expression were similar under both natural senescence and dark-induced senescence conditions. [ABSTRACT FROM AUTHOR]

This study aimed to develop a regional nutrient demand-based approach to assess the potential use of digestate nutrients from a planned biogas plant investment as a part of a regional circular economy concept. The assumed biogas plant is expected to treat urban wastes; biowastes (23,500 t/y) and sewage sludges (120,000 t/y) from the Tampere region, Finland (total population of 500,000). The calculation of the regional nutrient balance was based on the fertilizable crop areas, fertilization regimes and biomass nutrient amounts, with an assumption that livestock manures were primarily utilized in crop production. Subsequently, a Geographic Information System (GIS)-based methodology was applied to evaluate the transportation distances of nutrients from the biogas plant to the closest crop fields. As a result from the presented approach, livestock manure covered 41% and 12% of the phosphorus (P) and soluble nitrogen (N) need of the studied region. There was a residual potential for the regional utilization of biogas plant nutrients, which together with the livestock manure accounted for 50% of P and 15% of soluble-N need. Transportation of nutrients up to 40 km from the biogas plant is necessary if all nearby fields receive the waste-based nutrients, while the distance increased to 66 km if 30% of the local farmers are willing to use the nutrients. The approach presented in this study acts as a tool for planning nutrient cycles, which can be used to sustainably manage the regional nutrient flows when planning a new biogas plant investment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Assessment of ash from co-combustion of bark and sludges for nutrient recovery. • P amounts indicate that ash from co-combustion can be useful as a soil improver. • Morphology of slag particles was analysed with X-ray micro-tomography. • Overall, a high number of small and discrete pores. • Relatively thick particle walls and few pore openings indicates a need of grounding. Recycling phosphorus from waste streams for fertilization purposes could contribute to a sustainable society. The production in the pulp and paper industry results in several waste streams, among others nutrient-rich sludges in different forms. This study presents a detailed chemical and 3D characterization of ash from co-combustion of bark and two types of sludges from a paper mill; mixed sludge and biosludge. The combustion performance was investigated for these experiments and advanced analysis methods were used to characterise the ashes to correlate chemical and physical properties relevant for nutrient recycling. The elemental composition was determined by energy-dispersive X-ray spectroscopy; dominating crystalline phases by X-ray diffraction; and morphology, porosity, pore size distribution and active surface area of the slag were analysed with synchrotron-based X-ray micro-tomography and image analysis. Slag was formed in all combustion experiments to a large extent with increasing amounts with a higher proportion of sludge. Nutrient amounts indicate that slag particles from co-combustion of both biosludge and mixed sludge can be useful either as a soil improvement directly or for recovery processes. Slag from combustion of 30 wt% biosludge and 70 wt% bark contained the highest amount of phosphorus, 9 at % on a C and O free basis. Evaluation of tomography data showed that discrete and open pores could be distinguished on a micrometre scale. The porosity of the slag varied between the replicates and fuel mixtures, on average between 17 and 23 vol% for the bark and sludge mixtures. Open pore volume displayed large variations, on average 39–56 vol% of the pores were open pores connected to the surrounding volume. For all samples, 90 % of the pores were small, with an equivalent diameter under 30 μm, but the largest pore volume (80–90 %) consists of pores with an equivalent diameter over 75 μm. In soils, pores with a minimum equivalent diameter over 30 μm generally transmit water and the smaller pores store water. The slag particles have relatively thick walls, with few pore openings to the surroundings, indicating that the slag needs to be pre-treated by milling or crushing before application in the soil. [ABSTRACT FROM AUTHOR]

The polychaete Hediste diversicolor is known to recycle side streams from aquaculture and biogas production. We conducted a feeding experiment to evaluate whether rearing temperature or mixtures of these two side streams enhances biomass production and fatty acid composition. We reared H. diversicolor along a 5-temperature gradient ranging from 5.8 °C to 17.1 °C and a 4-step gradient form 100% aquaculture sludge to 100% solid biogas digestate. Formulated fish feed served as a control diet. Polychaetes increased growth rate with increasing temperature, ranging from 0.01 at 5.8 °C to 0.14 at 17.1 °C, while survival was inversely affected by temperature with 100% survival at 5.8 °C and 70% survival at 17.1 °C. Diet had a less pronounced effect on polychaete survival, and no significant effect on growth rates. Contrasting to growth, the fatty acid composition of the polychaetes was not affected by temperature but was highly influenced by diet, as polychaetes did not cluster by rearing temperature but by the diets they received. In conclusion, H. diversicolor can be utilized as a recycler of aquaculture and biogas side streams, and production temperature can be optimized for growth without compromising fatty acid composition and quality of the polychaetes. • We cultivated polychaetes along a temperature and food quality gradientby mixing aquaculture sludge and biogas digestate • Temperature had a significant effect on growth and survival of the polychaetes but not on fatty acid profiles • Diet had a pronounced effect on fatty acid composition of the polychaetes, but not on their growth and survival • We found an absence of homeoviscous adaptation in H. diversicolor • Cultivation temperature can be optimized for polychaete growth rates without compromising their nutritional value. [ABSTRACT FROM AUTHOR]

Boron (B) fertilizers are essential for global crop production. Sustainable B use demands a higher efficiency of B fertilizers through controlled B release and an enhanced B recycling from secondary sources, e.g. B-impregnated cellulose fiber insulation (CFI) waste. In this study, thermochemical treatments based on combustion and pyrolysis were investigated for processing CFI waste into a slow-release B fertilizer. Hot-water extractions of obtained materials confirmed that slow-release properties were achieved, and material characterization with XRD, FTIR and 11B-NMR showed that these were largely the result of formation of sparingly soluble Ca–B phases. A seedling toxicity test with fodder rape demonstrated the benefit of this slow-release B in comparison with conventional soluble B to circumvent toxicity, suggesting potential for B application via seed coatings. Finally, a fertilization trial with fodder rape and poppy seed showed that most slow-release B compounds were equally effective as soluble B at recommended B doses, while slow-release B can still benefit from reduced B leaching losses. [Display omitted] • Thermochemical processing of B-rich cellulose fiber insulation (CFI) was tested. • Obtained combustion and pyrolysis products had slow-release B characteristics. • Slow-release B was largely the result of formation of sparingly-soluble Ca–B phases. • B toxicity to plants could be avoided using treated CFI instead of soluble B. • In a plant fertilization trial, treated CFI was equally effective as soluble B. [ABSTRACT FROM AUTHOR]

Cycling of nutrients, such as phosphorus (P) and nitrogen (N), is essential for all life: Nutrients are crucial for securing societies' food systems and valuable raw materials for industrial processes. Recycling nutrients from various side and waste streams instead of virgin nutrients has attracted considerable interest in the society, particularly as geopolitical and epidemic issues have caused many nations to reconsider how they ensure flows of critical resources by increasing the Circular Economy (CE) principles. This study examines what drivers and barriers catalyze nutrient circulation in national settings, requiring diverse actors to support intentional nutrient recycling. By taking multidisciplinary and ecosystem approaches, we examine diverse sociotechnical drivers and barriers and the actor ecosystem involved. We conduct an extensive qualitative case study on nutrient circulation (P and N) in a Finnish context, analyzing over 150 documents and interviewing over 20 diverse actors (from diverse companies through ministries to farmers) involved in nutrient recycling, from biowaste through agricultural biomasses and sludge from municipal wastewater treatment plants. Our study 1) generates an ecosystem actor map uncovering diverse actors enabling nutrient recycling in society; and 2) exposes technological, business, organizational, regulatory, linguistic, visual, and psychological drivers and barriers shaping nutrient circulation. It explains the sociotechnical preconditions for different actor/stakeholder groups to adopt and advocate circular economy (CE) principles for nutrient recycling, which are generalizable to other critical resources. The study contributes to CE research and advises practitioners by providing a comprehensive catalyst toolbox to advance nutrient circulation and facilitate its acceptability and diffusion. [Display omitted] • Qualitative study analyzes drivers/barriers for recycling of critical resources, nutrients. • "Ecosystem" is applied as a metaphor for a multi-actor constellation enabling recycling. • Key actors for nutrient recycling ecosystem vary from farmers and businesses to policymakers. • Catalysts are technical, business, organizational, regulatory, linguistic, visual, and psychological. • A framework is developed for sociotechnical drivers advancing circular economy diffusion. [ABSTRACT FROM AUTHOR]

To promote circularity in agricultural systems, the utilization of aquatic vegetation for ecological wastewater treatment is a potential mechanism to capture and upcycle nutrients. Agricultural wastewater is an excellent growing medium for aquatic plants like duckweed, offering opportunities for wastewater treatment and conversion of harvested biomass into bio-based products, including protein-rich livestock feed, which can potentially replace conventional soil-based crops such as alfalfa. We hypothesize that nitrogen (N) and phosphorus (P) loadings to the Chesapeake Bay Watershed (CBW) can be reduced via replacing alfalfa cultivation with manure-grown duckweed by: a) reducing excess manure application on agricultural fields; b) reducing synthetic fertilizer application on alfalfa croplands; and c) decreasing the release of fixed N back into the environment from the decomposition of alfalfa crop residue. This study developed an optimization framework to identify locations where alfalfa-to-duckweed replacement could be theoretically employed to minimize N and P loads into the CBW. A relative effectiveness (RE) indicator representing landscape-specific nutrient delivery capacity was included within the framework. Using county-level data on alfalfa yields, cropping area, and nutrient inputs from alfalfa croplands and dairy manure, we identified alfalfa cultivation areas that could be removed and replaced with full or partial duckweed cultivation and land conservation for optimal benefits. At the county scale, counties in Pennsylvania (especially Lancaster and adjacent regions) with widespread farming operations and high RE values consistently indicated the greatest benefit by replacing large areas of alfalfa cultivation (> 80% in each county) with duckweed. Using nutrient load minimization as the primary objective function, a 2.9% N reduction and 2.4% P reduction can be achieved at the watershed scale by converting only 7.6% of the total alfalfa cropland area into duckweed farms. Upon introducing production cost minimization as a competing second objective function, up to 12.8% N reduction and 9.2% P reduction are possible with a 40% decrease in the alfalfa cropping area. A 10-year economic analysis demonstrated the possibility for superior return on investment with this approach, leading to almost seven times the baseline net revenue with alfalfa production, primarily attributed to the higher protein content and corresponding revenue potential of duckweed. Many different constraints on alfalfa production (ex., maintaining some baseline production) and duckweed replacement strategies (ex., utilization of decommissioned alfalfa area vs. soil conservation) were used in this study, which offer a wide range of optimal solutions that consider both environmental and economic tradeoffs. [Display omitted] • Duckweed can be used to recover nitrogen (N) and phosphorus (P) from dairy wastewater. • Nutrient loadings to the Chesapeake Bay Watershed (CBW) can be reduced by replacing alfalfa cultivation with duckweed. • Spatial optimization identified locations for alfalfa-to-duckweed replacement to minimize N and P loads to the CBW. • A load reduction of 12.8% N and 9.2% P is possible with a 40% decrease in alfalfa area. • High protein duckweed yields almost 7 times the baseline net revenue of alfalfa production. [ABSTRACT FROM AUTHOR]

Microalgae are an important source of oils and other molecules that can be used as feedstocks to produce biofuels and high-value products, having the potential of becoming a significant renewable energy source. However, large scale production of microalgal biofuels faces numerous technical challenges, which makes the current growth and development of the microalgae biorefinery industry, still economically unviable. This study reviewed the recently released information regarding the upstream methodologies involved in an algae-based biofuels production system. The better understanding of the conversion of light to biomass, the analysis of the productivities of the most recent culture systems, the use of waste waters as alternative sources of nutrients, and the co-location of the algae biomass production process to an industry are among the approaches that have been proposed to track the challenges in the development of a biorefinery system based on microalgae; these have been analyzed critically in this work. [ABSTRACT FROM AUTHOR]

The present study examined the effects of three recirculation rates (50%, 200% and 400%) on water quality and biomass growth at low and high fish stocking densities (122 and 220 fish/m 3 ) in aquaponic systems. The system consisted of a Tilapia tank connected to a gravel filter and three hydroponic trenches in series with Ipomoea aquatica , Lactuca sativa and Canna glauca . The RRs influenced most water quality parameters with best water quality at the high RR. At the low RR of 50% mass mortality of fish occurred due to lack of oxygen. The fish growth and survival was excellent in the high RR of 400% at the low fish density of 122 fish/m 3 . The plant trenches were found to be effective in removing potential harmful concentrations of NH 4 -N and NO 2 -N from the recirculating water. For each kg of fish produced in this system approximately 1.0 m 3 water was needed. During a 25-day period about 1 kg of marketable fresh biomass of I. aquatica and 270 g dry weight aboveground biomass of C. glauca was produced. It is concluded that high recirculation rate of the water of 200–400% per day is needed to secure a good growth and a low FCR of Tilapia in aquaponic systems. High recirculation rates also secure a good water quality. The aquaponic system has a very low effluent discharge compared to traditional aquaculture techniques, and it recycles nutrients for plant growth. Hence, aquaponic system is a promising sustainable solution that can be applied on commercial fish pond scale. [ABSTRACT FROM AUTHOR]

In order to create sustainable systems for resource management, residues from cooking and ecological sanitation (EcoSan) can be employed in recycling-driven soil fertility management. However, the link between energy, sanitation, and agricultural productivity is often neglected. Hence, the potential self-sufficient nature of many smallholdings in sub-Saharan Africa is underexploited. Objective To compare those cooking and sanitation technologies most commonly used in north-western Tanzania with locally developed alternatives, with respect to (i) resource consumption, (ii) potential to recover resources, and (iii) environmental emissions. This study examines technologies at the household level, and was carried out using material flow analysis (MFA). The specific bioenergy technologies analysed include: three-stone fires; charcoal burners; improved cooking stoves (ICS), such as rocket and microgasifier stoves; and biogas systems. The specific sanitation alternatives studied comprise: pit latrines; two approaches to EcoSan; and septic systems. Results The use of ICS reduces total resource consumption; using charcoal or biogas does not. The residues from microgasifiers were analysed as having a substantial recovery potential for carbon (C) and phosphorus (P). The fact that input substrates for biogas digesters are post-agricultural in nature means that biogas slurry is not considered an ‘untapped resource’ despite its ample nutrient content. Exchanging pit latrines for water-based sanitation systems places heavy pressure on already scarce water resources for local smallholders. In contrast, the implementation of waterless EcoSan facilities significantly promotes nutrient recovery and reduces environmental emissions, particularly through greenhouse gas emission and nutrient leaching. Conclusions Recycled outputs from the triple energy-sanitation-agriculture nexus display complementary benefits: residues from cooking can be used to restore organic matter in soils, while sanitation residues contribute to fertilisation. The combination of microgasifiers and EcoSan-facilities is the most appropriate in order to simultaneously optimise resource consumption, reduce environmental impacts, and maximise recycling-based soil management in smallholder farming systems. [ABSTRACT FROM AUTHOR]

Nutrient recycling is essential to make microalgae cultivation sustainable at industrial scale. To this aim, lab-scale anaerobic digestion experiments of Chlorella vulgaris after lipid extraction were carried out to evaluate biogas yield and nutrients recovery in the liquid digestate. Then, this liquid fraction was used as source of nutrients for cultivation of a closely related C. vulgaris species, in order to assess the possibility of re-cultivating microalgae towards a closed-loop nutrient recycling process. The biological methane potential tests resulted in biogas production of about 347 NmL gVS −1 with 43% v/v methane content. In re-growth experiments, the liquid digestate showed an insufficient amount of soluble sulfate and phosphorus. However, by amending these two nutrients, the specific growth rate and final biomass concentration increased to about 2 d −1 and 2 g L −1 , respectively, which were comparable to those obtained in a defined control medium. The low content of soluble phosphorus in liquid digestate was mainly due to precipitation and removal with the solid phase. Several techniques were hence tested to enhance phosphorus solubilisation, and highest recoveries of up to 41% were obtained when using NaHCO 3 . Finally, C. vulgaris was grown in such treated digestate, obtaining a final biomass production comparable to that of the control, without the need of external phosphorus supply. [ABSTRACT FROM AUTHOR]

Solutions for resource scarcity should be sought from urban waste management and sanitation, which are characterised by central plants and long networks. The socio-technical transition to more sustainable infrastructure is expected to include partial decentralisation based on local conditions. This paper focuses on drivers, barriers and enablers in implementing a decentralised circular system in a new residential area (Tampere, Finland). In the alternative system, biowaste and feces are treated in a local biogas plant, and nutrient and energy output are utilised within the area. This research aims to understand what kind of urban planning enables alternative infrastructure, as well as the characteristics of an innovation capable of making a breakthrough. Seventeen infrastructure planning experts were interviewed, then assembled to re-develop ideas arising from the interviews. Based on these qualitatively analysed data, 11 factors which help the adoption of the alternative system were formulated. The results indicate that sustainability transition can be facilitated through impartial urban planning that allows the early participation of actors and improved communications. Additionally, studying the impact of alternative solutions and city guidance according to environmental policy aims may enhance transition. Innovation success factors include suitable locations, competent partners, mature technology and visible local benefits. [ABSTRACT FROM AUTHOR]

Relatively little research has been conducted to date on farmer attitudes towards the use of fertilisers from resource–oriented sanitation systems. This study employed a psycho–sociological approach to identify factors that encourage, or discourage, negative and positive attitudes to human waste recycling among farmers in southern India. A survey involving face–to–face interviews was performed with 120 randomly sampled farmers, taking into account the following factors: gender, age, religion, caste, type of farming, farm size, annual income and farming history. Variations in variables (χ 2 and ANOVA) were considered statistically significant if p –value was < 0.05. When asked whether they thought human wastes could be used as fertiliser, of the farmers who expressed an opinion 59% were positive to re–use of urine and 46% to re–use of human faeces. Farmers in Vellore appeared to display what we term, a ‘ not–in–my–circle ’ syndrome, as they would prefer their neighbours to use human urine rather than their friends, family and colleagues. The main factors that motivated farmers to respond positively to re–use of urine were improved soil quality and potential cost savings from reduced use of chemical fertilisers. Fear of crop die–off, fear of being ridiculed and uncertainty over consumer marketplace behaviour were significant factors among farmers with a negative attitude. Furthermore, the survey responses indicated that besides socio–demographic factors, other factors such as ‘ trust ’ might have to be taken into consideration when planning and implementing nutrient recycling programmes. Early dialogue, continuous interaction and integration of user stakeholders (producers and consumers) in conceptualisation, design and implementation of nutrient recycling programmes are essential to ensure future success and wider adoption. [ABSTRACT FROM AUTHOR]

A novel eco-engineered mixed anaerobic culture was successfully demonstrated for the first time to be capable of continuous regeneration in nutrient limiting conditions. Microbial catabolism has been found to support a closed system of nutrients able to enrich a culture of lithotrophic methanogens and provide microbial cell recycling. After enrichment, the hydrogenotrophic species was the dominating methanogens while a bacterial substratum was responsible for the redistribution of nutrients. q-PCR results indicated that 7% of the total population was responsible for the direct conversion of the gases. The efficiency of H 2 /CO 2 conversion to CH 4 reached 100% at a gassing rate of above 60 v/v/d. The pH of the culture media was effectively sustained at optimal levels (pH 7–8) through a buffering system created by the dissolved CO 2 . The novel approach can reduce the process nutrient/metal requirement and enhance the environmental and financial performance of hydrogenotrophic methanogenesis for renewable energy storage. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine if polycultures of algae could enhance tolerance to aqueous-phase coproduct (ACP) from hydrothermal liquefaction (HTL) of algal biomass to produce biocrude. The growth of algal monocultures and polycultures was characterized across a range ACP concentrations and sources. All of the monocultures were either killed or inhibited by 2% ACP, but polycultures of the same species were viable at up to 10%. The addition of ACP increased the growth rate (up to 25%) and biomass production (53%) of polycultures, several of which were more productive in ACP than any monoculture was in the presence or absence of ACP. These results suggest that a cultivation process that applies biodiversity to nutrient recycling could produce more algae with less fertilizer consumption. [ABSTRACT FROM AUTHOR]

Phosphorus is essential to life on Earth and frequently limits the productivity of ecosystems, including agroecosystems. Currently, a substantial portion of the global human population relies on finite phosphate rock resources used for chemical fertilizer production. Concern over poor management of these vital resources and continued efforts to enhance soil fertility and food security have stimulated interest in phosphorus recovery and recycling. Existing heterogeneity in phosphorus waste flows, agricultural phosphorus needs, the availability of resources, and spatial patterns of land use calls for a diverse array of phosphorus recycling strategies. Ecological engineers working on phosphorus management have most commonly aimed to create phosphorus sinks on the landscape to help mitigate eutrophication. There is a growing need for ecological engineering approaches that go beyond phosphorus retention to create pathways for phosphorus recovery and recycling, supporting both eutrophication control and food security. This review includes a brief overview of human impacts on the global phosphorus cycle and a survey of existing ecological engineering techniques for phosphorus recovery and recycling discussed in the literature. A systems approach for design and feasibility assessment of phosphorus recycling with eco-technology is outlined, along with several key challenges. The importance of an interdisciplinary, multiple element, and multiple resource approach to phosphorus recycling is emphasized. [ABSTRACT FROM AUTHOR]

• The concentration of nitrogen (N) and phosphorus (P) in minke whale faeces off Svalbard, Norway, is 50.1 ± 10.3 and 70.9 ± 12.1 g per kg dry matter, respectively. • The population of 15,000 minke whales in the Svalbard area in Norway defecate daily 7 ± 1.4 tonnes (t) N and 10 ± 1.7 t P during summer. • The molar ratio of N:P in minke whale faeces was 1.6:1, meaning that N was proportionally limiting. • The release of P through defecation has the potential to stimulate 407 ± 70 t of carbon per day. This amounts to 0.2 to 4 % of daily net primary production in the region. There is increasing interest in assessing the impact of whales on nutrient and carbon cycling in the ocean. By fertilising surface waters with nutrient-rich faeces, whales may stimulate primary production and thus carbon uptake, but robust assessments of such effects are lacking. Based on the analysis of faeces collected from minke whales (n = 31) off Svalbard, Norway, this study quantified the concentration of macro and micronutrients in whale faeces prior to their release in seawater. Concentrations of the macronutrients nitrogen (N) and phosphorous (P) in minke whale faeces were 50.1 ± 10.3 and 70.9 ± 12.1 g kg−1 dry weight, respectively, while the most important micronutrients were zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu). By combining measured faecal nutrient concentrations with estimated prey-consumption and prey-assimilation rates, we calculate that the current population of approximately 15, 000 individuals in the small management area (SMA) of Svalbard defecates daily 7 ± 1.4 tonnes (t) N and 10 ± 1.7 t P during summer. The molar ratio of N:P in minke whale faeces was 1.6:1, meaning that N was proportionally limiting, when compared to average elemental ratios of 16:1 in phytoplankton. In case of no N limitation in surface waters at that time, the release of elemental P through defecation in surface waters has the potential to stimulate 407 ± 70 t of carbon per day during summer as new or regenerated primary production in the SMA of Svalbard. This amounts to 0.2 to 4 % of daily net primary production in this region. This study provides the first assessment of nutrient concentration in whale faeces prior to their dissolution in sea water. Further research, namely on the amount of N released via urine and seasonal changes in excreted nutrients, is needed to better assess the full potential of whale nutrient additions to dissolved nutrient pools in surface waters at regional and global scales. [ABSTRACT FROM AUTHOR]

This study proposes a cascade processing of the lipid-rich microalgae Auxenochlorella protothecoides. Freshly harvested biomass is pre-concentrated to 100 g/kg susp and then pretreated using pulsed electric fields (PEF). PEF-treatment, which affects permeability of cells membrane, induces a spontaneous release of microalgal ingredients into the surrounding medium, mostly carbohydrates and micronutrients, which can be recovered. After separation of this aqueous fraction, lipid extraction is performed on the remaining wet pellet using an ethanol-hexane blend. After recovery of those different valuables, it was considered, to convert the rest biomass (cell envelope and most of the other remaining hard- or non-extractable components), to storable energy. Anaerobic digestion (AD) of the remains to biogas was considered to be a promising solution. AD-processes have the charm that unprocessed wet microalgal biomass, as well as wet organic biomass residues from previous extraction steps can be utilized directly without further purification or drying steps. The obtained biogas can then be upgraded to methane for an energetic use. PEF-treated algal biomass showed a 10 % increased methane outcome (467 mL norm /g VS) compared to the untreated sample. PEF-treated microalgae, subjected to extraction of the aqueous fraction, demonstrated a 23 % increase in methane yield (558 mL norm /g VS), compared to control. Finally, the biomass, PEF-treated and subjected to extraction of water fraction and lipids, still achieved 41 % of methane potential (205 mL norm /g VS) during the AD process, compared to the untreated control. Our study demonstrates the feasibility of cascade processing using PEF-treatment. Moreover, all the study was developed keeping in mind industrial requirements. In particular, our downstream approach did not require any drying, the pretreatment required low amount of energy, i.e. 1.5 MJ/kg CDW and the majority of the biomass was valorized. Since all techniques used, especially PEF-pretreatment, can be up-scaled, we believe this approach has great potential for implementation in industry. [Display omitted] • Pulsed electric field (PEF) suits to further anaerobic digestion (AD) of microalgae. • PEF-treated, aqueous- and lipid extracted microalgae still have potential for AD. • PEF-treatment and aqueous extraction increase specific methane yield. • Molecules, liberated by PEF-treatment, induce a delay in AD but no final inhibition. [ABSTRACT FROM AUTHOR]

Keeping horses causes environmental impacts through the whole chain from feed production to manure. According to national statistics, the number of horses in Sweden is currently 360,000 and is continuing to increase. This result in increasing amounts of horse manure that has to be managed and treated, which is currently done using practices that cause local, regional, and global environmental impacts. However, horse manure and its content of nutrients and organic material could be a useful fertiliser for arable land and a substrate for renewable energy production as biogas. The aim of the paper is to identify and describe potentially critical factors in horse keeping determining the amount (total mass) and characteristics (nutrient content and biodegradability) of horse manure, and thus the potential for anaerobic digestion. A systematic combining approach is used as a structural framework for reviewed relevant literature. All factors identified are expressed as discrete choices available to the horse keeper. In all, 12 different factors were identified: type and amount of feed, type and amount of bedding, mucking out regime, residence time outdoors, storage type and residence time of manure in storage, spreading and soil conditions, and transport distance and type of vehicle fuel used. Managing horses in terms of these factors is of vital importance in reducing the direct environmental impacts from horse keeping and in making horse manure attractive as a substrate for anaerobic digestion. The results are also relevant to environmental systems analysis, where numerical calculations are employed and different biogas system set-ups are compared to current and other treatments. In such assessments, the relevance and importance of the critical factors identified here and corresponding conditions can be examined and the most promising system set-up can be devised. [ABSTRACT FROM AUTHOR]

Hydrothermal Liquefaction (HTL) for algal biomass conversion is a promising technology capable of producing high yields of biocrude as well as partitioning even higher quantity of nutrients in the aqueous phase. To assess the feasibility of utilizing the aqueous phase, HTL of Nannochloropsis sp. was carried out in the temperature range of 275 to 350 °C and Residence Times (RT) ranging between 5 and 60 min The effect of reaction conditions on the NO 3 − , PO 4 3 − , SO 4 2 − , Cl − , Na + , and K + ions as well as Chemical Oxygen Demand (COD) and pH was investigated with view of recycling the aqueous phase for either cultivation or energy generation via Anaerobic Digestion (AD), quantified via Lifecycle Assessment (LCA). It addition to substantial nutrient partitioning at short RT, an increase in alkalinity to almost pH 10 and decrease in COD at longer RT was observed. The LCA investigation found reaction conditions of 275 °C/30 min and 350 °C/10 min to be most suitable for nutrient and energy recovery but both processing routes offer environmental benefit at all reaction conditions, however recycling for cultivation has marginally better environmental credentials compared to AD. [ABSTRACT FROM AUTHOR]

Efficient use and recycling of resources by utilizing nutrients of waste water and CO 2 from flue gases are considered through comparing two conceptual systems: a conventional small scale waste water treatment plant (base case) and a waste water treatment plant combined with algae cultivation unit (algae case). The used algae case concept is based on interviews of experts working with algae cultivation in Finland. Hotspots related to the algae case are assessed from environmental perspectives. According to model calculations, in high latitudes effective algae production may be achieved, although the areal production rates are very low in winter. In the algae case concept nutrients of waste water can be more effectively recycled using bio-based chitosan as flocculant. Also energy is produced in the biogas production plant, which increases the resource recycling of the algae case. When considering the energy balance, a positive net energy ratio (NER) >1 is possible to achieve with maximum methane production potential of algal biomass. [ABSTRACT FROM AUTHOR]

The physical profile and chemical composition of growing media are vital in evaluating fish waste filtration efficiency and plant growth performance in aquaponics. The present study reported and compared the physical and chemical evaluation of the novel fabricated Kaolina, gravel, and commercially used lightweight expanded clay aggregate (LECA) as growing medias in aquaponics. Field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDX) was utilized to analyze the growing media's chemical composition and structural characterization. The resultant effect of these growing medias on water quality and the growth performance of Clarias gariepinus and Lactuca sativa were also reported. Kaolina exhibited an excellent physical profile (42.95 ± 1.39%) in water absorption capacity as compared to LECA (35.90 ± 1.28%) and gravel (1.97 ± 0.25%), showing a significant difference at p < 0.05. The addition of 25% w/w Musa paradisiaca peel in the fabrication of Kaolina gives an added value of 88.0% of K and 100% of P elements, which show a significant difference (p < 0.05) compared to LECA. The results obtained reveal a better daily growth rate (DGR) and relative growth rate (RGR) of L. sativa at 0.57 ± 0.02 cm day−1 and 0.21 ± 0.00 g day−1, respectively. Results indicated that the porous structure of growing media could contribute to the high-water retention capability and slow the water desorption process. Hence, it could increase the ability of the growing media to hold nutrients for plant intake, resulting in higher removal percentage of nutrients in aquaponics system. Kaolina gives the highest nutrient removal percentage of TAN (96.86 ± 1.50%), NO 2 − (83.56 ± 1.27%), NO 3 −(77.55 ± 0.48%), and PO 4 3− (79.46 ± 0.42%). The results also shown growing media has considerable impacts on nutrient removal, which contribute to the aquaponic productions. [Display omitted] • Nutrient supplies through Kaolina are more natural and sustainable. • Kaolina eliminate chemical nutrient supply practiced in aquaponics. • Water absorption and retention capacity of Kaolina is more stable. • Kaolina provided essential micronutrients and optimized physical characteristics. • Significant yield of L. sativa and C. gariepinus in Kaolina than LECA and gravel. [ABSTRACT FROM AUTHOR]

Nutrient recovery from wastewater in the form of acids/bases by electrodialysis with bipolar membranes or diffusion dialysis facilitates the current demand for a green economy and circular production. However, bipolar membranes are sensitive to scaling, mainly by calcium and magnesium salts, as well as to biofouling caused by microbial growth and linked aspects. This work aimed to reduce divalent cations to a value below 10 ppm and DOC content of a residual liquid waste stream after microbial fermentation and before a bipolar electrodialysis/diffusion dialysis step for nutrient and acid/base recovery. In this context, three pretreatment technologies were analyzed: nanofiltration, electrodialysis with monovalent cation-exchange membranes, and ion-exchange resins. Nanofiltration and electrodialysis with monovalent cation-exchange membrane were demonstrated to be suitable pretreatments with 92–96 % Mg2+ and Ca2+ removal and 86–94 % DOC removal. Ion-exchange resins had excellent divalent cation removal but no DOC removal, therefore requiring additional treatment to remove organic substances and prevent membranes' biofouling. Electrodialysis with monovalent cation-exchange membranes was preferable over nanofiltration due to the 1.6-fold concentration factor for sulfate ions. In contrast, nanofiltration had lower energy consumption and higher stability in divalent cation rejection. Results obtained in this study are valuable for selecting an appropriate treatment for resource recovery and water reclamation from industrial wastewater and for biotechnological downstream processes. [Display omitted] • ED with standard AEM and monovalent CEM was tested for divalent cation removal. • ED was compared with conventional pretreatment: nanofiltration and ion exchange. • ED had the highest DOC removal (95 %) and 1.6-fold concentration factor for SO 4 2-. • Nanofiltration had the lowest energy consumption and 86 % DOC removal. • Sulfonic acid IER had higher capacity for Mg2+ and Ca2+ removal than iminodiacetic. [ABSTRACT FROM AUTHOR]

A novel and efficient organic waste management strategy currently gaining great attention is fly larvae composting. High resource recovery efficiency can be achieved in this closed-looped system, but pharmaceuticals and pesticides in waste could potentially accumulate in every loop of the treatment system and spread to the environment. This study evaluated the fate of three pharmaceuticals (carbamazepine, roxithromycin, trimethoprim) and two pesticides (azoxystrobin, propiconazole) in a fly larvae composting system and in a control treatment with no larvae. It was found that the half-life of all five substances was shorter in the fly larvae compost (< 10% of control) and no bioaccumulation was detected in the larvae. Fly larvae composting could thus impede the spread of pharmaceuticals and pesticides into the environment. [ABSTRACT FROM AUTHOR]

Two sustainable management models were studied, in order to investigate if they were successful in satisfying the nutritional needs of mature olive groves (20 year-old olive trees- Olea europaea , cv. ‘Koroneiki’), situated in two geographical regions of Greece (Thessaloniki, Central Macedonia, Northern Greece, and Corfu, Ionian Islands, Western Greece). Nutrient supply in both olive orchards was based, during the last 20 years, on pruning material recycling, as well as on cow manure (8 t/ha/year, in the grove of Corfu) and patent kali (5 kg/tree/year, in the grove of Thessaloniki) application. Soil analysis revealed that pH was slightly alkaline in the olive grove of Thessaloniki and acidic (6.00–6.34) in the olive orchard of Corfu; organic matter content was approximately two times greater in the grove of Corfu. Exchangeable Ca concentrations in deeper soil layers (20–40 and 40–60 cm) of the olive orchard of Thessaloniki were approximately two times greater, compared to those found in the grove of Corfu. In contrast, 2–14.5 times greater K exchangeable concentrations, but only in deeper layers (20–40 and 40–60 cm), were found in the grove of Corfu. DTPA extractable Fe, Mn and Zn concentrations were 9–14, 3–5, and 3–5.5 times greater (depending on soil layer) in the olive orchard of Corfu, compared to those found in Thessaloniki. Leaf K concentrations were significantly greater in the grove of Corfu (1.2–1.4% d.w.), while Fe concentrations in the same olive orchard exceeded 120 ppm. Generally, most of the leaf nutrient concentrations for both groves were within the normal levels of sufficiency, or within the over-sufficiency range (e.g. those of N and K in the grove of Corfu, and P in both olive orchards). Only leaf B concentrations in January (17–19 p.p.m.), in both orchards, and leaf Mn levels in the grove of Corfu were slightly (but not seriously) deficient to marginal. Consequently, it can be concluded that both studied sustainable management models for mature olive groves (no soil tillage, pruning material and weed cuts recycling, in addition to: (i) patent kali, or (ii) manure supply) were successful. Thus, the two models are commercially and environmentally sustainable for olive cultivation, especially in marginal, degraded, and/or hilly Mediterranean areas. Finally, they are of great socioeconomic importance in specific rural areas (where olive-growers combine olive oil production with domestic animal breeding). [ABSTRACT FROM AUTHOR]

Improvement in nutrient recycling in agriculture is essential to maintain food production while minimising nutrient pollution of the environment. For this purpose, understanding and modelling nutrient cycles in food and related agro-industrial systems is a crucial task. Although nutrient management has been addressed at the plot and farm scales for many years now in the agricultural sciences, there is a need to upscale these approaches to capture the additional drivers of nutrient cycles that may occur at the local, i.e. district, scale. Industrial ecology principles provide sound bases to analyse nutrient cycling in complex systems. However, since agro-food social-ecological systems have specific ecological and social dimensions, we argue that a new field, referred to as “Agro-Industrial Ecology”, is needed to study these systems. In this paper, we review the literature on nutrient cycling in complex social-ecological systems that can provide a basis for Agro-Industrial Ecology. We identify and describe three major approaches: Environmental Assessment tools, Stock and Flow Analysis methods and Agent-based models. We then discuss their advantages and drawbacks for assessing and modelling nutrient cycles in agro-food systems in terms of their purpose and scope, object representation and time-spatial dynamics. We finally argue that combining stock-flow methods with both agent-based models and environmental impact assessment tools is a promising way to analyse the role of economic agents on nutrient flows and losses and to explore scenarios that better close the nutrient cycles at the local scale. [ABSTRACT FROM AUTHOR]

The production of vegetables relies on the use of mineral fertilizers which are based either on fossil fuel (e.g., nitrogen fertilizers based on Haber–Bosch process) or on fossil ore deposits (phosphate rock). On the other hand, nutrient recovery processes generate various end and side products that can provide a sustainable alternative for fossil-based mineral fertilizers. Their use however, is currently limited by insufficient knowledge about the properties and the impact of these products on soil quality and crop yield. This research was aimed to evaluate the use of the liquid fraction of digestate, effluent from constructed wetlands originating from a manure/digestate treatment facility, air scrubber water and struvite in the cultivation of lettuce ( Lactuca sativa L.) compared to their conventional fossil-based counterparts. In accordance with the crop nutrient requirements, different fertilization treatments were set up in which individual products and combinations were tested. At harvest time, assessment of soil physicochemical properties was conducted, along with crop quality control. Nutrient balances were determined and an economic and environmental assessment was evaluated. There were no significant differences in crop yield and soil quality at harvest time between conventional fossil-based mineral fertilizers and selected bio-based mineral alternatives. Nitrogen and potassium use efficiencies were slightly lower in treatments with bio-based fertilizers. Moreover, economic and ecological assessment have shown higher benefits for the farmer when bio-based alternatives were used as a replacement for synthetic fertilizers. Re-use of these products should be stimulated in European legislation. [ABSTRACT FROM AUTHOR]

Picochlorum sp. strain SENEW3 is a halotolerant green alga with high growth rates and the ability to utilize organic nitrogen sources including wastewater generated from hydrothermal liquefaction (HTL-WW). Picochlorum acclimates to the presence of HTL-WW. In a photosynthesis/respiration rate test, Picochlorum SENEW3 showed a stress response to HTL-WW additions in a dose-dependent manner while cells pre-grown with HTL-WW had a greatly reduced response to additions. A quantitative proteomics tool, iTRAQ, was applied to assess Picochlorum global proteome changes in response to HTL-WW as a nitrogen source. From this approach, a total of 350 different proteins were identified across 2 biological replicates which were significantly up-regulated or down-regulated (average ratio of more than 1.2 or less than 0.8, at least one p-value of < 0.05). Protease and oxidative stress enzymes were notably up-regulated. An aminopeptidase enzyme assay showed that, compared to controls, cells grown with 0.1% (vol) HTL-WW had 2.1-fold higher protease activity. An ascorbate peroxidase assay showed an 8.6-fold increase in exponential cells grown with 0.1% HTL-WW compared to controls. This study provides insights into the development of microalgae for algal biofuel production using HTL wastewater recycling [1]. [ABSTRACT FROM AUTHOR]

The suitability of crude and purified struvite (MgNH 4 PO 4 ), a major precipitate in wastewater streams, was investigated for renewable replacement of conventional nitrogen and phosphate resources for cultivation of microalgae. Bovine effluent wastewater stone, the source of crude struvite, was characterized for soluble N/P, trace metals, and biochemical components and compared to the purified mineral. Cultivation trials using struvite as a major nutrient source were conducted using two microalgae production strains, Nannochloropsis salina and Phaeodactylum tricornutum , in both lab and outdoor pilot-scale raceways in a variety of seasonal conditions. Both crude and purified struvite-based media were found to result in biomass productivities at least as high as established media formulations (maximum outdoor co-culture yield ∼20 ± 4 g AFDW/m 2 /day). Analysis of nutrient uptake by the alga suggest that struvite provides increased nutrient utilization efficiency, and that crude struvite satisfies the trace metals requirement and results in increased pigment productivity for both microalgae strains. [ABSTRACT FROM AUTHOR]

A two-stage hydrothermal liquefaction process was used to reduce nitrogen heteroatoms in algae biocrude and generate an aqueous co-product stream for algae cultivation. A low temperature liquefaction pretreatment (PT: 125–225°C, 0.5–30 min) hydrolyzed proteins and partitioned nitrogen to the aqueous phase, which was separated and analyzed for nutrient and toxin concentrations. The retained solids (20%) were subjected to hydrothermal liquefaction (HTL) in the second step at 350°C for 60 min. The low temperature pretreatment was most effective at higher temperatures and holding times (225°C, 15 min), removing 45% of the nitrogen present in the algae solids, while retaining 59% of the solid mass, yet reduced overall bio-oil yields by 35 to 71% relative to single stage HTL. Experiments conducted in two-chamber reactors with increased heating rates, resulted in similar nitrogen removal levels at shorter residence times (250°C, 5 min). When coupled with high-temperature HTL, pretreatment improved the elemental content of the biocrude by increasing the total nitrogen removed and reducing nitrogen heteroatom content by 26–28%, compared to HTL alone. The aqueous co-product stream was analyzed for nutrient availability and indicated potential for recycle and algae cultivation due to its high nitrogen and phosphorus levels, moderate pH, and low inhibitory compound concentrations. [ABSTRACT FROM AUTHOR]

Despite environmental benefits of algal-biofuels, the energy-intensive systems for producing microalgae-feedstock may result in high GHG emissions. Trying to overcome energy-costs, this research analyzed the biodiesel production system via dry-route, based on Chlorella vulgaris cultivated in raceways, by comparing the GHG-footprints of diverse microalgae-biodiesel scenarios. These involved: the single system of biomass production (C0); the application of pyrolysis on the residual microalgal biomass (cake) from the oil extraction process (C1); the same as C0, with anaerobic cake co-digested with cattle manure (C2); the same conditions as in C1 and C2, by integrating in both cases (respectively C3 and C4), the microalgae cultivation with an autonomous ethanol distillery. The reduction of GHG emissions in scenarios with no such integration (C1 and C2), compared to CO, was insignificant (0.53% and 4.67%, respectively), whereas in the scenarios with integration with ethanol production system, the improvements were 53.57% for C3 and 63.84% for C4. [ABSTRACT FROM AUTHOR]

With the ever-increasing size of anaerobic digesters (AD), the management and disposal of digestate have become a challenging task for AD operators. Anaerobic digestate is rich in nutrients and contaminants; thus, a suitable treatment is required to meet environmental legislation and protect the receiving environment. There has been a thrust among the research efforts in anaerobic digestate management in the last decade. Volarization of digestate into high-value products is necessary to make the AD process more cost-effective. Moreover, digestate utilization helps in recycling the already mined resources. Efforts have been made to use digestate as a feedstock to recover energy and value-added products such as nutrients (N, P), biochar, biofuels, polyhydroxyalkanoates (PHAs), and algal cultivation, which can arguably help to enable the circular economy in modern communities. This communication thoroughly examines the anaerobic digestate-based biorefinery concept and its linkages with the circular bio-economy. This review comprehensively summarized digestate management practices; recovery of renewable fuels and other value-added products from digestate, including bottlenecks and perspectives altogether in digestate management and treatment. The state-of-the-art of commercialization of anaerobic digestate valorization technologies has also been provided. Overall, this review could support decision-makers in identifying environmentally sound and sustainable solutions ahead of time. [Display omitted] • Critically review of the conventional and emerging digestate management practices. • Featured the commercialization of anaerobic digestate valorization technologies. • Key challenge & research needs in development of digestate valorization are explored. • Various pre-treatment methods can be used to improve the quality of nutrients recovered. • Presence of emerging contaminants is a major concern in digestate utilization. [ABSTRACT FROM AUTHOR]

The use of biochar to recover nitrogen and phosphorus from wastewater especially source-separated human urine is attractive from both economic and environmental standpoints. The widespread use of pharmaceuticals has raised concerns as they are not fully metabolized and ended up in human urine. The objective of this study is to examine adsorption of antibiotics (azithromycin, ciprofloxacin, sulfamethoxazole, trimethoprim, and tetracycline) and nutrients (ammonium and phosphate) in source-separated human urine by biochar and subsequent desorption. Batch adsorption experiments were conducted using biochar prepared from oak wood (OW) and paper mill sludge (PMS) to elucidate the effects of adsorption time, pH, and adsorbent dose. The desorption of adsorbed nutrients and antibiotics was also investigated. While the nutrient adsorption was more favorable by the PMS biochar, antibiotic adsorption was more prolific by the OW biochar. Hydrogen bonding and π-π interaction were identified as potential adsorption mechanisms. Experimental results agree with the Freundlich isotherm and pseudo-second order models (except the OW biochar for the kinetics). The findings suggest that biochar can adsorb both nutrients (43.30–266.67 mg g−1) and antibiotics (246.70–389.0 μg g−1) simultaneously. Lower solution pH (<5) was better for antibiotic adsorption, while higher solution pH (≥5) favored nutrient recovery. Also, desorption of the antibiotics (maximum of 92.6% for trimethoprim) was observed and might arise in the environment with the applications of biochar for nutrient recovery from human urine and subsequently for soil quality improvement. The findings serve as a foundation for future research on adsorption-based methods for separating nutrients and antibiotics in aqueous solutions, particularly urine. [Display omitted] • Biochars adsorbed nutrients and antibiotics in urine simultaneously. • Adsorption capacities of nutrients were better than those of antibiotics. • Adsorption mechanisms of nutrients and antibiotics were pH dependent. • Hydrogen bonding and π-π interaction were adsorption mechanisms. [ABSTRACT FROM AUTHOR]

On-farm measures can be used in multi-barrier schemes to manage microbial risks from consumption of wastewater-irrigated vegetables, especially where informality of the practice determines minimal external support for farmers. Evidence indicates that cessation of irrigation greatly reduces microbial contamination on leafy vegetables, but at the expense of produce quality. Replacing wastewater with higher-quality irrigation water during the last days of cultivation is an alternative to cessation of irrigation that does not compromise produce quality. This study evaluated the effect of wastewater substitution under on-farm conditions on different indicators of microbial contamination of lettuce. Lettuce was cultivated in experimental plots and irrigated with three water sources: spring water, water from a wastewater-polluted river and effluent from a primary wastewater treatment plant, but with the river water replaced by spring water in half the plots about two weeks before harvest. The experiment was repeated four times in different seasons. Irrigation water samples collected during cultivation and lettuce samples collected at harvest were analysed for helminth eggs, Escherichia coli and coliphages. Variables characterizing the irrigation practices and environmental conditions were recorded. There were no significant differences in helminth egg or E. coli concentrations on lettuce (medians ranged from −0.7 to −0.1 log 10 eggs g−1 and 0.6–1.4 log 10 cfu g−1, respectively) between any of the treatments involving wastewater irrigation; no statistical analysis was possible for coliphages because concentrations on lettuce were mostly at or below the detection limit (94% of samples). Variables associated with temperature and soil explained helminth egg and E. coli concentrations on lettuce, while number of days of irrigation with spring water (representing wastewater substitution) was significant only for E. coli. It was concluded that the experimental conditions were suboptimal for successful implementation of wastewater substitution for on-farm microbial risk management, but key variables for successful implementation were identified. • Extended die-off was studied for microbial reduction on wastewater-irrigated crop. • 11–14 days of die-off were achieved by replacing wastewater with a cleaner source. • Water, soil, and lettuce samples were taken during four crop cycles. • Studied microbes were reduced in < 1 log 10 by irrigation water substitution. • Reduction rates may be higher in warmer regions/with higher irrigation efficiencies. [ABSTRACT FROM AUTHOR]

The chemical absorption of carbon dioxide (CO 2 ) is a technique used for the mitigation of the greenhouse effect. However, this process consumes high amounts of energy to regenerate the absorbent and to separate the CO 2 . CO 2 removal by microalgae can be obtained via the photosynthesis process. The objective of this study was to investigate the cultivation and the macromolecules production by Spirulina sp. LEB 18 with the addition of monoethanolamine (MEA) and CO 2 . In the cultivation with MEA, were obtained higher results of specific growth rate, biomass productivity, CO 2 biofixation, CO 2 use efficiency, and lower generation time. Besides this, the carbohydrate concentration obtained at the end of this assay was approximately 96.0% higher than the control assay. Therefore, Spirulina can be produced using medium recycle and the addition of MEA, thereby promoting the reduction of CO 2 emissions and showing potential for areas that require higher concentrations of carbohydrates, such as in bioethanol production. [ABSTRACT FROM AUTHOR]

A growing body of evidence suggests that the jellyfish population in Chinese seas is increasing, and decomposition of jellyfish strongly influences the marine ecosystem. This study investigated the change in water quality during Cyanea nozakii decomposition using simulation experiments. The results demonstrated that the amount of dissolved nutrients released by jellyfish was greater than the amount of particulate nutrients. NH 4 + was predominant in the dissolved matter, whereas the particulate matter was dominated by organic nitrogen and inorganic phosphorus. The high N/P ratios demonstrated that jellyfish decomposition may result in high nitrogen loads. The inorganic nutrients released by C . nozakii decomposition were important for primary production. Jellyfish decomposition caused decreases in the pH and oxygen consumption associated with acidification and hypoxia or anoxia; however, sediments partially mitigated the changes in the pH and oxygen. These results imply that jellyfish decomposition can result in potentially detrimental effects on marine environments. [ABSTRACT FROM AUTHOR]

Corals are critical in supporting high productivity and biodiversity in oligotrophic seawaters by recycling nutrients. Here, we constructed a model of nitrogen cycling in coral endosymbionts, which provides a mechanism for the efficient nutrient metabolism of corals. First, we conducted a long-term 15 N-labelling experiment on corals using flow-through aquaria, where 15 N-labelled nitrate was continuously supplied to the corals Porites cylindrica and Montipora digitata for two months. After the labelling experiment, 15 N isotope ratios were measured in the algal endosymbionts and their animal host and the nitrogen (N) dynamics through the endosymbiont cells were modelled. The model calculations showed that the algal endosymbionts in P. cylindrica and M. digitata derived an average of 80% and 50% of their N from the animal host, respectively. The finding indicates that the large N pool in the coral animal tissue plays an important role in supporting endosymbiotic function, photosynthesis, and consequent coral reef growth. The species-specific difference in available internal N was attributed to N biomass of the animal host per unit coral surface area. Algal N uptake from seawater was enhanced by 20% with the addition of phosphate in seawater. Thus, active endosymbiotic algal photosynthesis in oligotrophic seawater may be related to their dependence on the host-derived phosphorus as well as N. [ABSTRACT FROM AUTHOR]

Microalgal biomass of the green algae Acutodesmus obliquus produced in photobioreactors was converted during hydrothermal gasification into biogas. The liquid residues from this process contain mainly inorganic elements which may substitute traditional nutrient sources. The conversion process produces two residual water fractions, an aqueous phase and a salt brine with a total recovery rate of the macronutrient nitrogen, 56.8% and 1.3% of phosphorus. Both types of residues were added in separate batch experiments to study the effects on growth of A. obliquus and Chlorella vulgaris over 9–10 days of cultivation. The biomass parameters and fatty acid productivity were assessed to elucidate the effects of the residues on the two algal species compared to a control culture medium. It was demonstrated that especially the salt brine can substitute fertilizers for algal cultivation. However not all the nutrients originally brought into the gasification process could be recovered, so the aqueous phase was replenished with nutrients. Biomass productivities of A. obliquus and C. vulgaris grown in the aqueous phase from the conversion process were similar to those in the control culture medium and reached up to 1.3 g L − 1 d − 1 and 0.5 g L − 1 d − 1 , respectively. Fatty acid productivity of A. obliquus in the aqueous phase was 312.9 mg L − 1 d − 1 , thus similar to the control. A much lower productivity of only 43.5 mg L − 1 d − 1 was determined for C. vulgaris with aqueous residue which accounted for only 52.6% of the control. The results indicate that the residual water from hydrothermal gasification can be partly applied as a sole nutrient source for large scale production of algal biomass and can also be a sustainable substitute for commercial fertilizers. [ABSTRACT FROM AUTHOR]

Many authors have focused on the contribution of inner farm nutrient recycling to closed nutrient cycles, but little is known about the contribution of exchanges among farms to nutrient cycling. By using a network approach, we assessed the structure of farm mass flows networks and their consequences for nitrogen (N), phosphorus (P) and potassium (K) recycling in organic farming at the local scale. Organic farming was considered as a prototype of farming systems that aims at better closing nutrient cycles. Inflows and outflows were collected for two cropping years on 63 organic farms. The farms were located in three French agricultural districts with areas ranging from 520 to 1021 km 2 and differentiated by their degree of specialization (specialized in crop production, animal production, or mixed). Local nutrient recycling was assessed at the district scale through: (i) the local supply, defined as the ratio of the amount of nutrients from exchanges among farms plus the amount of nitrogen from atmospheric sources, to the sum of inputs to organic farms; and (ii) the cycling index, defined as the fraction of nutrients flowing at least twice through the same farms. Results showed that exchanges among farms were mainly short-distance exchanges (<50 km on average) and contributed up to 70% of farm nutrient inflow. Mass flows among farms were two to four times greater in the mixed district than in specialized districts. As a consequence, both the local supply and the cycling index were greater in the mixed district than in the specialized districts. However, even if the local supply was generally high (85%, 52% and 54% for N, P and K inflows in the mixed district, respectively), the cycling index remained low (5%, 20% and 10% for N, P and K in the mixed district), indicating that most flows among farms were one-way and not actual nutrient recycling. This study contributes to the understanding of the magnitude, conditions and factors of nutrient recycling in agriculture at the local scale. [ABSTRACT FROM AUTHOR]

In this study, the reuse of nitrogen from fuel-extracted algal residues was investigated. The alga Scenedesmus acutus was found to be able to assimilate nitrogen contained in amino acids, yeast extracts, and proteinaceous alga residuals. Moreover, these alternative nitrogen resources could replace nitrate in culturing media. The ability of S. acutus to utilize the nitrogen remaining in processed algal biomass was unique among the promising biofuel strains tested. This alga was leveraged in a recycling approach where nitrogen is recovered from algal biomass residuals that remain after lipids are extracted and carbohydrates are fermented to ethanol. The protein-rich residuals not only provided an effective nitrogen resource, but also contributed to a carbon “heterotrophic boost” in subsequent culturing, improving overall biomass and lipid yields relative to the control medium with only nitrate. Prior treatment of the algal residues with Diaion HP20 resin was required to remove compounds inhibitory to algal growth. [ABSTRACT FROM AUTHOR]

Our study examines the relative importance of the causal linkages between exogenous total phosphorus (TP) loading and internal nutrient recycling with the water quality conditions in Lake Simcoe, Ontario, Canada. We enhance the mechanistic foundation of a simple TP mass-balance model, originally developed to guide the eutrophication management in the system. The structural improvements include the incorporation of macrophyte dynamics, the explicit representation of the role of dreissenids in the system, and the improved portrayal of the interplay between water column and sediments. Our model provides good agreement with the observed TP variability in the system during the study period (1999–2007). Consistent with empirical evidence, our model predicts that macrophyte uptake from the interstitial waters is responsible for a significant loss of P from the sediments. Our model also suggests that dreissenids filter a considerable amount of particulate P from the water column, but the effective clearance rate is significantly lower with a substantial amount of the filtered particles (> 85%) returned into the water column as faeces, pseudofeces or other metabolic excreta. P diffusive fluxes from the sediments account for about 30–35% of the exogenous P loading in Lake Simcoe. The sediments in the main basin are mostly driven by fast diagenetic processes of settling organic matter from the epilimnion, suggesting an internal P loading of 9.2 tonnes yr − 1 . Finally, our study attempts to explain the lack of distinct decreasing trends in ice-free TP concentrations after the invasion of dreissenid mussels, suggesting that the presence of active nutrient recycling pathways, potentially magnified by the particular morphological features and hydrodynamic patterns of Lake Simcoe, could counterbalance the direct effects of dreissenid filtration. [ABSTRACT FROM AUTHOR]

Our study presents a biogeochemical model that aims to reproduce the ecological processes shaping phytoplankton dynamics in the shallow hypertrophic lagoon of Albufera de Valencia (Spain). The model simulates two elemental cycles (N and P), two phytoplankton groups (cyanobacteria and non-cyanobacteria), and heterotrophic bacteria. First, we examine the capacity to reproduce the observed plankton patterns, while accommodating the uncertainty related to the external forcing factors of our model (hydraulic and nutrient loading, zooplankton grazing). Sensitivity analysis is also performed to identify the most influential parameters and therefore to shed light on the knowledge needed to solidify the model parameter specification. We subsequently utilize the calibrated model to assess the phytoplankton response to potential restoration actions; namely, the interplay between external nutrient loading reductions and variant flushing rates. The model successfully simulates a number of relevant water quality variables in the system, including total chlorophyll a , nitrate, ammonia, total nitrogen and total phosphorus. According to our sensitivity analysis, the credibility of the model as a management tool is primarily dependent upon the characterization of the phytoplankton growth strategies and associated settling rates. External P and N loadings are identified as the predominant driver of the system dynamics and their control should remain the main priority of local management efforts. Finally, we pinpoint future research directions that could advance our understanding of the ecosystem functioning, including an improved quantitative description of the seasonal variability of the hydraulic regime in the studied lagoon. [ABSTRACT FROM AUTHOR]

Protection measures are needed to control nutrient leaching from agriculture to the Baltic Sea. Ecological Recycling Agriculture (ERA) is based on local nutrient resources, integrating animal and crop production on farms or in their proximity. In Finland, three agricultural study catchments were chosen to demonstrate environmental impacts of ERA. Inorganic nitrogen (N) leaching from the catchments was simulated with INCA-N model in prevailing and ERA farming conditions. Lepsämänjoki catchment is a crop production area, in the Yläneenjoki catchment animal husbandry is common and in the Lestijoki catchment the main production line is dairy production. A theoretical crop rotation was developed to represent ERA cultivation consisting of leys, cereals and mixture of cereals and pea. N fixation, mineralization and manure were sources of N. INCA-N was calibrated in the catchments using present cultivation practices. Next, crop parameters were modified to describe ERA cultivation. The model results showed that ERA has potential to decrease N losses: the highest inorganic stream N concentrations and average annual inorganic N losses from agricultural fields decreased, compared to those resulting from present production relying on inorganic fertilizers. Therefore, ERA may serve as one of the measures to achieve the N reduction targets set for agriculture in the Baltic Sea Action Plan. [ABSTRACT FROM AUTHOR]

To reduce wastes and the costs of microbial lipid production, it is imperative to recycle resources, including spent cell mass, mineral nutrients and water. In the present study, lipid production by the oleaginous yeast Rhodosporidium toruloides was used as a model system to demonstrate resources recycling. It was found that the hydrolysates of spent cell mass were good media to support cell growth of various oleaginous yeasts. When serial repitching experiments were performed using 70 g/L glucose and the hydrolysates alone as nutrients, it produced 16.6, 14.6 and 12.9 g/L lipids, for three successive cycles, while lipid titre remained almost constant when spent water was also recycled. The cell mass hydrolysates could be used as equivalents to the mixture of yeast extract and peptone to support lipid production from corn stalk hydrolysates. Our results showed efficient recycling of lipid production wastes and should be helpful to advance microbial lipid technology. [ABSTRACT FROM AUTHOR]