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• Cities benefit from nutrient circularity integrating waste and local agriculture. • Significant benefits from biogas generation and avoiding mixed waste treatment. • Nutrient concentrations in urban agricultural soils limit application of compost. • Local regulations and soil quality hinder nutrient circularity in urban areas. Cities face the challenges of supplying food and managing organic municipal solid waste (OMSW) sustainably amid increasing urbanization rates. Urban agriculture (UA) can help with this effort by producing local crops that are fertilized with nutrients recovered from compost generated from OMSW. This research aims to determine the potential of OMSW compost to supply the nitrogen-phosphorus-potassium (NPK) demand of UA and the environmental benefits of replacing mineral fertilizer from a life cycle perspective. The Metropolitan Area of Barcelona (AMB) serves as the case study given its commitment to reuse biowaste according to the Revised Waste Framework Directive and to promote UA as a signing member of the Milan Urban Food Policy Pact. Based on crop requirements and farmer surveys, we find that the annual NPK demands of the agricultural fields of the AMB that cover 5,500 ha and produce 70,000 tons of crops are approximately 769, 113, and 592 tons of NPK, respectively. Spatial material flow analysis and life cycle assessment were applied to found that the current waste management system can potentially substitute 8 % of the total NPK demanded by UA with compost, reduce the impacts by up to 39 % and yield savings in global warming of 130 %. The more ambitious future scenario of 2025 can potentially substitute 21 % of the total NPK demand and reduce environmental impacts up to 1,049 %, depending on the category considered. Avoiding processing of mixed OMSW, mineral fertilizer replacement and cogeneration of electricity from biogas are the major contributors to these environmental savings. [ABSTRACT FROM AUTHOR]

• Field experiment in mandatory recycling scheme tests effectiveness of door stepping. • Majority of households in mandatory recycling schemes separates waste correctly. • Minority of households is responsible for most miss sorting. • Door stepping does not influence behavior of households in mandatory schemes. • Door stepping can improve recycling behavior in voluntary recycling schemes. Household organic waste has great potential for closing nutrient cycles in agriculture. This requires proper waste separation by households. Personal communication at the doorstep potentially improves household waste separation behaviour but it is expensive and findings from existing research are mixed. Based on results of previous studies and from a quasi-experiment with non-equivalent groups design in two German municipalities, this paper argues that efficiency of personal communication depends on its context. It can positively influence behaviour when recycling is voluntary and participation rates are low. However, it has no significant effects if recycling is mandatory. One explanation could be different perceptions of recycling in mandatory and voluntary schemes. In voluntary schemes door stepping can activate the intrinsic motivation of households. In mandatory schemes, all households need to participate irrespective of intrinsic motivation. This research shows that this creates a situation in which a small share of households is responsible for almost all contamination. This can be overcome by considering extrinsic factors that affect recycling behaviour. The paper recommends further research to understand which combination of incentives, sanctions and information is efficient in affecting behaviour change in mandatory recycling schemes. [ABSTRACT FROM AUTHOR]

• Mathematical modeling was applied to choose an optimal digestate processing route. • The model estimated the economic feasibility of the optimal solution. • The method challenges case-by-case designing projects and manual data collection. • The economic optimum and full exploitation of the recycling potential conflicted. Nutrients can be circulated back to agriculture from waste streams through anaerobic digestion and digestate processing. Digestate processing, however, is making slow progress as circulated nutrient products have not been cost competitive compared to fossil fertilizers and not designed from the farmer's perspective to truly match with the regional nutrient need. In this study, the aim is to assess apply mathematical optimization to the design of a cost-optimal processing route for a biogas plant's digestate to produce fertilizer products based on specified regional needs. Another aim is to analyze whether such a cost-optimal solution can fully exploit the nutrient recycling potential, that is, the efficiency of such a solution in returning nutrients to agriculture. The results indicate that mathematical optimization allows the design of a cost-optimal digestate production routes based on the region's nutrient need and characteristics. The true cost optimum was found for a design combining three processing technologies and producing four nutrient products, which when mixed, would fulfil farmer's fertilization needs. However, there seems to be a conflict between an optimal economic design and a full exploitation of recycling potential as only 25% of the digestate's phosphorus was utilized within the case region. This is because only 29% of the digestate mass was used and processed as fertilizer, as the concentration of required nutrients was deemed too low for economic use. The proposed mathematical model could be implemented as tool to assist in biogas plant investment decisions. [ABSTRACT FROM AUTHOR]

• >150 organic metabolites are oxidised over chloride and urea in unconcentrated, non-hydrolysed urine acidified to pH 3.0. • Heat-activated peroxydisulphate removed >50% TOC and degraded >40% ΣOMs with <10% nitrogen loss. • Heating real, unconcentrated urine acidified to pH 3.0 at 90 °C for 1 h activated >90% of 60 mM peroxydisulphate. • Concentrated urine had lower persulfate activation but higher chloride & urea degradation compared to unconcentrated urine. The human urine metabolome is complex, containing a wide range of organic metabolites that affect treatment of urine collected in resource-oriented sanitation systems. In this study, an advanced oxidation process involving heat-activated peroxydisulphate was used to selectively oxidise organic metabolites in urine over urea and chloride. Initial experiments evaluated optimal conditions (peroxydisulphate dose, temperature, time, pH) for activation of peroxydisulphate in unconcentrated, non-hydrolysed synthetic urine and real urine acidified to pH 3.0. Subsequent experiments determined the fate of 268 endogenous organic metabolites (OMs) and removal of COD from unconcentrated and concentrated real urine (80–90% mass reduced by evaporation). The results revealed >90% activation of 60 mM peroxydisulphate in real unconcentrated urine heated to 90 °C for 1 h, resulting in 43% ΣOMs degradation, 22% COD removal and 56% total organic carbon removal, while >94% of total nitrogen and >97% of urea in real unconcentrated urine were recovered. The mechanism of urea degradation was identified to be chemical hydrolysis to ammonia, with the rate constant for this reaction determined to be 1.9 × 10−6 s−1 at pH 3.0 and 90 °C. Treating concentrated real urine resulted in similar removal of COD, ΣOMs degradation and total nitrogen loss as observed for unconcentrated urine, but with significantly higher chloride oxidation and chemical hydrolysis of urea. Targeted metabolomic analysis revealed that peroxydisulphate treatment degraded 157 organic metabolites in urine, of which 67 metabolites were degraded by >80%. The rate constant for the reaction of sulphate radicals with oxidisable endogenous organic metabolites in urine was estimated to exceed 108 M−1 s−1. These metabolites were preferentially oxidised over chloride and urea in acidified, non-hydrolysed urine treated with peroxydisulphate. Overall, the findings support the development of emerging urine recycling technologies, including alkaline/acid dehydration and reverse osmosis, where the presence of endogenous organic urine metabolites significantly influences treatment parameters such as energy demand and product purity. [ABSTRACT FROM AUTHOR]

• In UV-free controls, urease activity in water and synthetic urine was similar, and higher than in real urine. • No urease activity was detected in water, synthetic urine and real urine after UV treatment. • Electrical energy demand to inactivate urease in real urine was 25-fold higher than synthetic urine. • Organic metabolites in real urine absorbed radiant flux and inhibited urease inactivation. In source-separating sanitation systems, inhibiting urease activity prevents enzymatic urea hydrolysis and volatilisation of ammonia when urine is concentrated by evaporation. This study tested UV-based photoinactivation as a novel alternative to existing methods of inactivating urease that require dosing urine with acid, base or oxidants. The enzymatic activity of jack bean (Canavalia ensiformis) urease in water, synthetic fresh urine and real fresh urine was investigated, with and without a 15 W low-pressure UV lamp that emitted 185 nm and 254 nm radiation. In UV-free controls, urea was hydrolysed at a rate of 3.2 × 10−3 mmol mg urease −1 min−1, 3.3 × 10−3 mmol mg urease −1 min−1 and 2.0 × 10−3 mmol mg urease −1 min−1 in water, synthetic urine and real urine, respectively. In the presence of UV, no urease activity was detected in any matrix. A UV irradiation time of 1.3 and 3.3 min was needed for inactivating urease in water and synthetic urine, respectively, whereas an irradiation time of 71 min was needed for inactivating urease in real urine. Overall, the electrical energy demand for photoinactivation of urease in real human urine was estimated to be 29.1 kWh m−3. Photolysis and photo-oxidation of amino acid residues at the active site of the enzyme were likely reasons for inactivation. Organic metabolites in real urine affected photoinactivation by (i) absorbing radiation between 190 nm and 400 nm, which reduced incident radiant flux; and (ii) scavenging hydroxyl radicals, which impeded oxidative damage to the enzyme. Overall, the findings demonstrate the feasibility of on-site treatment using a low-pressure UV lamp for inactivating urease in freshly excreted urine. [ABSTRACT FROM AUTHOR]

[Display omitted] • C. vulgaris -S395-2- C. rosea for aquaculture wastewater treatment were proposed. • Gibberellins enhances the attenuation of studied aquaculture pollutants. • Pollutant attenuation showed a high fungus strains dependence. • The maximum OTC removal efficiencies were 98.29 % ± 1.15 %. This study assessed the effect of gibberellins (GAs) concentrations on antibiotic and nutrient removal using diverse microalgal-bacterial-fungal consortia. Five systems (Chlorella vulgaris , T1; C. vulgaris + S395-2 + Clonostachys rosea, T2; C. vulgaris + S395-2 + Ganoderma lucidum , T3; C. vulgaris + S395-2 + Pleurotus pulmonarius , T4; and C. vulgaris + S395-2, T5) were established, and optimal conditions and effective symbiosis were applied to improve antibiotic and nutrient removal. Consortium growth was T2 > T3 > T5 > T4 > T1, while GA impact ranked 50 mg L–1 > 20 mg L–1 > 80 mg L–1 > 0 mg L–1. After 7 days at 50 mg L–1 GAs, total nitrogen (TN), NH 4 -N, NO 3 -N, and total phosphorous (TP) removal reached 85.97 %, 78.08 %, 86.59 %, and 94.39 %, respectively. Florfenicol, oxytetracycline hydrochloride, ofloxacin, and sulfamethoxazole removal efficiencies were 67.77 %, 98.29 %, 90.47 %, and 94.92 %, respectively. These findings highlight GAs' significant role in enhancing antibiotic and nutrient removal. [ABSTRACT FROM AUTHOR]

Phosphorus (P) in societal waste streams can be recycled and used as recycled P fertilisers (RPFs). When developing new technologies for P recycling, life cycle assessment (LCA) can be used to assess their environmental impact and support environmentally friendly decisions. In LCA calculations, inventory factors describe, for example, the emissions, resource requirements and potential substitution of products. The Phosphorus Life Cycle Inventory (PLCI) model is a tool for estimating such inventory factors for the use of RPFs. The main objective of this study was to develop the PLCI model from its previous parameterisation for Denmark to make it applicable to all countries and regions of the EU. This was undertaken by considering parameters that describe regional conditions affecting the loss of P, crop P uptake and potential mineral fertiliser substitution. Such parameters include soil type, soil P status, soil erosion, groundwater leaching, crop types, productivity and crop P concentrations. Several RPFs were incorporated into the model, including coefficients describing the partitioning to the labile, plant-available P fraction. To illustrate the applicability of the model, a case study was performed. Applications of RPFs were modelled in the Copenhagen region in Denmark and the Piedmont region in Italy. The higher soil erosion rate in Piedmont resulted in over six times greater P loss than in Copenhagen. The difference in P fertilisation practice between the regions had a strong impact on the mineral fertiliser substitutions. The results point to the importance of defining the fertilisation regime of the region being modelled, and this is now possible with the new, more dynamic version of PLCI. In conclusion, the new PLCI 2.0 model provides a dynamic tool for LCA practitioners to estimate region-specific inventory factors for RPFs. The model is relatively easy to use and captures differences between fertilisers with varying P availability and between applications in different regions of the EU. [Display omitted] • A life cycle inventory model for recycled P fertilisers was developed. • Regionalisation allowed differentiation in fertilisation effects between regions. • The model was applied to case studies in Denmark and Italy. • Higher soil erosion in Piedmont caused six times higher P loss than in Copenhagen. • The model captured differences between fertilisers with varying P availability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sewage sludge can be used as substitute for conventional fertilizer resources; • Organo-mineral fertilizers optimized for maize and sunflower crops were produced; • The share of waste materials in organo-mineral fertilizers was 49–54%; • Fertilizer production based on waste allows for organic matter and nutrient recycling. The depletion of natural resources, energy consumption and environmental issues relating to fertilizer production processes are driving a move towards a more sustainable use of resources and the recycling of nutrients. With regard to the fertilizer industry, this gives the opportunity to use the fertilizing potential of alternative raw materials. This paper evaluates the possibility of using dried sewage sludge in the manufacture of organo-mineral fertilizers. Fertilizers based on sewage sludge with an addition of poultry litter ash and mineral fertilizers were developed and characterized in the study. It was possible to produce multicomponent organo-mineral fertilizers with optimized compositions for maize and sunflower crops, characterized by total nutrient content over 20%. Moreover, they contained beneficial secondary nutrients and micronutrients originated from waste materials. The fertilizers were free of pathogens and fulfilled the requirements related to heavy metal content according to Polish legislation. The method of manufacturing organo-mineral fertilizers based on waste materials is a simple waste management solution offering organic matter and nutrient recycling in line with the circular economy and reducing reliance on imported raw materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Morphology of P-rich ash particles were analysed with X-ray micro-tomography. • Discrete and open pores were distinguished on a micrometre scale. • High porosity where 72–99 vol% was open pores connected to the surrounding volume. • Thin particle walls and open pores may promote weathering upon soil application. • Pore openings over 200 µm provides an opportunity for root and microbe interaction. Combustion of phosphorus-rich residual streams can produce nutrient-rich ashes and these can be used either in further processing or as materials for direct nutrient recycling. The latter requires knowledge on morphological parameters of such ash particles that may impact plant growth, nutrient availability, and soil physical properties. The present work aims to determine the porosity, pore size, and specific surface area of ash particles, and discuss these properties in light of literature concerning interaction with soil water and plant roots. Bottom ash particles from combustion of sewage sludge and wheat straw and their co-combustion were analysed with X-ray microtomography. Image analysis provided information on morphology, specific surface area, porosity, and pore structure on a micrometre scale resolution. Co-combusting sewage sludge with wheat straw resulted in differences in ash particles' porosity and pore structure compared to combustion of pure fuels. Pure wheat straw ash displayed 62 vol% porosity while there was no apparent difference between 10 wt% or 30 wt% mixtures of sewage sludge, with a porosity of 29–31 vol%. Open pore volume comprise the largest part of the porosity (72–99 vol%) enabling interaction between surrounding pore water and nutrients. Overall, the ash particles display large open volume fractions and thin particle walls which may lead to rapid weathering and extensive interaction with soil water. The particles generally contained pore openings over 200 µm towards the surroundings, which provide opportunities for interaction with microbes and roots from a variety of plant species in addition to nutrient transport by soil water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrodialytic and Gas Permeable Membrane are combined for nutrients recovery. • Two nitrogen- and phosphorus-rich solutions were used on biofertilizers synthesis. • 81% of phosphorus present in municipal waste was recovered as biofertilizers. • Struvite synthesized with alternative materials showed good properties. The recovery of valuable materials from waste fits the principle of circular economy and sustainable use of resources, but contaminants in the waste are still a major obstacle. This works proposes a novel approach to recover high-purity phosphorus (P) and nitrogen (N) from digestate of municipal solid waste based on the combination of two independent membrane processes: electrodialytic (ED) process to extract P, and gas permeable membranes (GPM) for N extraction. A laboratory ED cell was adapted to accommodate a GPM. The length of waste compartment (10 cm; 15 cm), current intensity (50 mA; 75 mA) and operation time (9 days; 12 days) were the variables tested. 81% of P in the waste was successfully extracted to the anolyte when an electric current of 75 mA was applied for 9 days, and 74% of NH 4 + was extracted into an acid-trapping solution. The two purified nutrient solutions were subsequently used in the synthesis of a biofertilizer (secondary struvite) through precipitation, achieving an efficiency of 99.5%. The properties of the secondary struvite synthesized using N and P recovered from the waste were similar to secondary struvite formed using synthetic chemicals but the costs were higher due to the need to neutralize the acid-trapping solution, highlighting the need to further tune the process and make it economically more competitive. The high recycling rates of P and N achieved are encouraging and widen the possibility of replacing synthetic fertilizers, manufactured from finite sources, by secondary biofertilizers produced using nutrients extracted from wastes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Decomposition was studied at surface and in caves along an elevational gradient. • Overall decomposition levels were comparable in above and below ground habitats. • At the surface abiotic and biotic factors correlate only with decomposition rate. • In caves abiotic and biotic parameters are associated with stabilizing factor. • Current predictions underestimate the net carbon budget in areas with caves. Decomposition is a major contributor to ecosystem respiration, determining the carbon emission and nutrient cycling rates. Our current understanding of decomposition dynamics and their underlying drivers has mainly focused on surface habitats but largely ignored in subterranean environments. Here we studied abiotic and microbial drivers of early-stage litter decomposition inside and outside caves along an elevational gradient in Tenerife. We found comparable decomposition rates (k) and litter stabilizing factors (S), with contrasting drivers and elevational variation. At the surface, we observed a mid-elevational trend in k , which tended to correlate with water availability, cooler temperatures, nutrient availability, and surface-specific bacterial taxa. In sharp contrast, caves showed no elevational impact nor influence of abiotic parameters and bacterial communities on k. Despite this, we found higher levels of S in caves, which were associated mainly with reduced water availability, lower temperatures and cave-specific bacterial taxa, indicating that conditions in caves are strongly linked with carbon storage. Our findings imply that our current perception of terrestrial habitat-based carbon cycling are underestimating the net carbon budget in areas with caves. Disentangling the role of the environment on decomposition in caves is key to fully characterize their roles in nutrient cycling and to understand how increasing anthropogenic pressures will affect fundamental processes in subterranean ecosystems. [ABSTRACT FROM AUTHOR]

The increase in soil salinization due to global climate change could cause large losses in crop productivity affecting, among other biological processes, to germination and seedling development. We have studied how salt stress affects nucleic acid degrading activities in radicles of common bean during seedling development. In radicles of common bean, a main nuclease of 37 kDa and two ribonucleases of 17 and 19 kDa were detected. Saline stress did not alter these three activities but induced a new ribonuclease of 16 kDa. All three ribonucleases are acidic enzymes that were inhibited by Zn. The 16 and 17 kDa ribonucleases are inhibited by guanilates. In the genome of common bean, we have identified 13 genes belonging to the T2 ribonuclease family and that are grouped in the 3 classes of T2 ribonucleases. The analysis of the expression of the 3 genes belonging to Class I (PvRNS1 to 3) and the unique gene from Class II (PvRNS4) in radicles showed that PvRNS3 is highly induced under salt stress. • The T2 ribonuclease (RNase) family in French bean is composed by 13 members grouped in three classes. • Three main RNases are detected in radicles under salt stress, being one of them absent under non stress conditions. • PvRNS3 , a Class I member, is highly induced in radicles under salt stress. [ABSTRACT FROM AUTHOR]

Land application of biosolids is a primary means of recycling human waste products globally; however, because biosolids are also heavily enriched with nutrients and pollutants, it is necessary to consider the environmental impacts of land applications in various agro-ecosystems. To reduce costs and divert waste, biosolids from Joint Base Lewis-McChord, a military installation south of Tacoma, WA, USA, are composted with organic materials derived from the base itself. The potential for turfgrass management using the composted biosolids was tested in a field study at the military recreation facility, Eagles Pride golf course. The composted biosolids were surface-amended to golf course fairways (n = 3) at a rate of 46 Mg ha−1, in split applications, fall and spring, over two years, 2015 and 2016. Soil bacterial and fungal community responses were evaluated in amended and unamended soils from each fairway, along with soil chemical properties, including soil pH, total carbon (C), total nitrogen (N), and the C:N ratio. Soil microbial community analysis on soils sampled pre- and post-amendment did not demonstrate changes in community structure as a result of the composted biosolids application. Differences observed in soil microbial community structure appears to reflect edaphic and vegetative differences between fairways. Generally, correlations between soil properties and bacterial community OTUs were stronger than those with fungal OTUs, and predicted bacterial community functional analysis revealed several KO term groups were significantly correlated with soil TC and TN. Turfgrass biomass was unaffected, while leaf tissue N was increased by 4.5 and 10.6% in 2015 and 2016, respectively. These results suggest that amendment with composted biosolids does not strongly impact microbial communities across two years; however, long-term amendment could have affects that are not detected during this short-term study. • Golf course biosolids land applications may be a viable new disposal route. • Composted biosolids efficiently supplemented golf course N fertilizer applications. • Fairway turfgrass readily accumulates N available in composted biosolids. • Microbiome structure in fairways was most strongly impacted by edaphic factors. • Microbial nutrient cycling was predicted best by soil total C and N content. [ABSTRACT FROM AUTHOR]

• The fate of micronutrients and heavy metals upon digestate processing was studied. • Vibrating membrane filtration (VSEP) was used for treatment of liquid fractions. • Production of dischargeable water was possible using VSEP and a lagoon. • Concentrates from VSEP show potential for reuse as a green fertilizer. • Heavy metals may be extracted/recovered from thick fractions of digestate. This study aims to evaluate the full-scale performance of vibrating membrane filtration (VSEP) technology in resource recovery from the liquid fraction of digestates, while reducing macronutrient concentrations down to dischargeable water. Although increasing attention is paid to mass flow assessment of macronutrients, to date little is known about the fate of micronutrients and heavy metals upon digestate processing. In this research, process streams were characterized and mass balances for micronutrients and heavy metals were performed throughout a complete digestate processing train. The VSEP system operated with reversed osmosis membranes and followed by a lagoon was capable of producing dischargeable water according to Flemish regulatory standards. Concentrates produced by one VSEP filtration of the liquid fraction of digestate and dried thick fractions resulting from solid-liquid separation were rich in macro- and micronutrients, while heavy metal concentrations did not exceed regulatory standards. Hence, these products showed high potential for reuse in agriculture. [ABSTRACT FROM AUTHOR]

Use of recirculating aquaculture systems (RAS) to grow fish is on the rise. Fish feed typically contains 25–60% protein and is the only significant input in RAS. Fish recover 20–30% of the applied feed as biomass, and the unassimilated nitrogen is released into the water, mainly as ammonia, which is toxic to fish. Nitrification is the most common treatment practice, converting ammonia to the less toxic nitrate, and nitrogen removal is achieved by either water exchange or denitrification. The aim of this study was to develop and test a novel approach to remove nitrogen based on a microaerophilic assimilation side-reactor. In the suggested system, fish solid waste and dissolved nitrogen are assimilated into protein-rich microbial biomass, which has the potential to partially offset fish feed input. Initially, a theoretical model based on the system's nitrogen mass balance was established. Then, an intensive pilot-scale RAS was constructed, growing ∼50 kg fish/m3. The system consisted of a fish tank, solids filter, and microaerophilic assimilation reactor based on activated sludge treatment. Intrinsic solid waste and wheat-flour waste were used as carbon source. After a trial run of about 2.5 months, the RAS was tested for 101 days. Average total ammonia nitrogen, nitrite, and nitrate removal were 89.1, 69.4 and 100%, respectively. Of the introduced solids, over 82% were lost as carbon dioxide by respiration, 11.7% were recovered as microbial biomass and 6.5% as fish biomass, and only 0.6% remained in the water. Biomass organic content was similar to aquafeed and nitrogen content was equivalent to 40% crude protein. Daily energy demand for the system's designed capacity of 80 kg/m3 would result in a low energy consumption of 7.72 kW h/kg fish. Overall, a novel concept for sustainable production in intensive aquaculture was developed and successfully demonstrated in a pilot-scale RAS. Image 1041268 • A novel sustainable RAS based on assimilation side-reactor was modeled and tested. • TAN and NO 2 concentrations in the fish tank were < than 0.89 and 0.1 mg/L. • Low feed conversion ratio and energy consumption were demonstrated. • The collected biomass (biofloc) has 40% crude protein similar to aquafeed. [ABSTRACT FROM AUTHOR]

• A closed-loop system of fusel alcohol production and nutrient recycling. • 3.8 g/L of mixed fusel alcohols were produced from M. salina hydrolysates. • Cellular N and P remineralized from algae biomass was recovered as struvite. • Struvite was recycled for subsequent algae cultivation as the major N/P nutrient. Improving the economic feasibility is necessary for algae-based processes to achieve commercial scales for biofuels and bioproducts production. A closed-loop system for fusel alcohol production from microalgae biomass with integrated nutrient recycling was developed, which enables the reuse of nitrogen and phosphorus for downstream application and thus reduces the operational requirement for external major nutrients. Mixed fusel alcohols, primarily isobutanol and isopentanol were produced from Microchloropsis salina hydrolysates by an engineered E. coli co-culture. During the process, cellular nitrogen from microalgae biomass was converted into ammonium, whereas cellular phosphorus was liberated by an osmotic shock treatment. The formation of struvite from the liberated ammonium and phosphate, and the subsequent utilization of struvite to support M. salina cultivation was demonstrated. The closed loop system established here should help overcome one of the identified economic barriers to scale-up of microalgae production, and enhance the sustainability of microalgae-based chemical commodities production. [ABSTRACT FROM AUTHOR]

• ΣOMP degradation of 99% in water and 55% in urine after 80 min UV-AOP (2100 J m-2). • Energy demand to degrade OMPs in urine was 10-fold higher than in Milli-Q water. • Organic compounds in urine compete with OMPs for UV light and scavenge free radicals. • Nitrogen content in urine is preserved during UV AOP and can be recovered afterwards. In household wastewater, a large proportion of organic micropollutants (OMPs) load is attributed to human urine. OMPs could pose a risk to human and environmental health when urine collected in source-separating sanitation systems is recycled as crop fertiliser. This study evaluated degradation of 75 OMPs in human urine treated by a UV-based advanced oxidation process. Fresh urine and water samples were spiked with a broad range of OMPs and fed into a photoreactor equipped with a UV lamp (185 and 254 nm) that generated free radicals in situ. Degradation rate constant and the energy required to degrade 90% of all the OMPs in both matrices were determined. At a UV dose of 2060 J m-2, average ΣOMP degradation of 99% (±4%) in water and 55% (±36%) in fresh urine was achieved. The energy demand for removal of OMPs in water was <1500 J m-2, but for removal of OMPs in urine at least 10-fold more energy was needed. A combination of photolysis and photo-oxidation can explain the degradation of OMPs during UV treatment. Organic substances (e.g. urea, creatinine) likely inhibited degradation of OMPs in urine by competitively absorbing UV-light and scavenging free radicals. There was no reduction in the nitrogen content of urine during treatment. In summary, UV treatment can reduce the load of OMPs to urine recycling sanitation systems. [Display omitted] [ABSTRACT FROM AUTHOR]

Pyrolysis of calcium-rich feedstock (e.g., poultry manure) generates semi-crystalline and crystalline phosphorus (P) species, compromising its short-term availability to plants. However, enriching poultry manure with magnesium (Mg) before pyrolysis may improve the ability of biochar to supply P. This study investigated how increasing the Mg/Ca ratio and pyrolysis temperature of poultry manure affected its P availability and speciation. Mg enrichment by ∼2.1% increased P availability (extracted using 2% citric and formic acid) by 20% in Mg-biochar at pyrolysis temperatures up to 600 °C. Linear combination fitting of P K-edge XANES of biochar, and Mg/Ca stoichiometry, indicate that P species, mainly Ca–P and Mg–P, are altered after pyrolysis. At 300 °C, adding Mg as magnesium hydroxide [Mg(OH) 2 ] created MgNH 4 PO 4 (18%) and Mg 3 (PO 4) 2.8H 2 O (23%) in the biochar, while without addition of Mg Ca 3 (PO 4) 2 (11%) predominated, both differing only for pyrophosphate, 33 and 16%, respectively. Similarly, the P L 2,3 edge XANES data of biochar made with Mg were indicative of either MgHPO 4.3H 2 O or Mg 3 (PO 4) 2.8H 2 O, in comparison to CaHPO 4.2H 2 O or Ca 3 (PO 4) 2 without Mg. More importantly, hydroxyapatite [Ca 5 (PO 4) 3 (OH)] was not identified with Mg additions, while it was abundant in biochars produced without Mg both at 600 (12%) and 700 °C (32%). The presence of Mg formed Mg–P minerals that could enhance P mobility in soil more than Ca–P, and may have resulted in greater P availability in Mg-enriched biochars. Thus, a relatively low Mg enrichment can be an approach for designing and optimize biochar as a P fertilizer from P-rich excreta, with the potential to improve P availability and contribute to the sustainable use of organic residues. [Display omitted] • Phosphorus bioavailability increases in Mg-enriched biochar up to high pyrolysis temperatures. • OH− anions provided with Mg(OH) 2 could be a mechanism by which Mg-doped biochars have higher P availability. • Adding Mg to poultry manure decreased the formation of Ca–P minerals in low temperatures. [ABSTRACT FROM AUTHOR]

Root exudates are mainly composed of sugars, organic acids, and amino acids. These are carbon sources that recruit beneficial bacterial communities in the rhizosphere. However, the composition of the root exudates is variable and mainly unknown for plants from arid lands, such as Agave lechuguilla Torr. This work studied the effect of different metabolites identified in the rhizosphere of A. lechuguilla Torr. (Maltose, lactose, oxalic and tartaric acids, arginine, and methionine), over the enzymatic activity and abundance of nitrogen-fixing bacteria and organic phosphorus mineralizing bacteria, as well as the changes in the nutrient availability in the soil. It was found that only the amino acids increased the nitrogenase and phosphatase activity, and these increments were reflected in the available nutrient concentration in the soil. Likewise, the presence of carbon and nitrogen from the amino acids may reduce the C:N ratio in the soil, enhancing the mineralization of organic matter and the concentration of ammonia, nitrite, and nitrates. This work shows the complexity of the nutrient recycling process in the soil and the essential role of bacteria in making nutrients available to plants. Understanding this process could aid in improving the establishment of plants in eroded ecosystems or under the harsh conditions of arid environments. [Display omitted] • This is the first description of the root exudates composition of A. lechuguilla. • Nitrogen fixation and mineralization in soil improved with Arg and Met addition. • Sugars and amino acids favored a priming effect in the bacterial communities. [ABSTRACT FROM AUTHOR]

Abstract To provide sufficient quantities of food and feed, farming systems have to overcome limiting factors such as the nutrient depletion of arable soils. Nitrogen being the main mineral element required for plant growth, has led to the extensive use of chemical fertilizers causing nitrogen pollution of the ecosystems. This field study investigates the use of biogas residues (BRs) as biofertilizers and their contribution to the mitigation of nitrate leaching in agricultural soils, while also demonstrating the polluting nature of chemical fertilizers. Nine different fertilization treatments classified in three schemes and two nitrogen doses were tested for three consecutive years on a grassland in the Walloon Region of Belgium. Residual soil mineral nitrogen, percentage contribution of treatments in residual nitrate and agronomic performance were assessed for each fertilization treatment. The results obtained showed significant differences on treatment and scheme level regarding nitrate accumulation in the soil, with chemical fertilizers posing the highest nitrate leaching risk. BRs did not cause nitrate accumulation in the soil, and were N rate and rainfall independent, while the chemical treatments indicated a cumulative tendency under high N rate and low precipitation. Forage yield did not demonstrate statistical differences on treatment and scheme level but varied with changing precipitation, while the maximum application rate suggested a plateau. Aboveground nitrogen content was significantly higher after the application of chemical fertilizers only in the first year, while all the chemical treatments indicated a dilution effect under elevated annual rainfall. Finally, the partial substitution of chemical fertilizers by raw digestate reduced the concentration of NO 3 − in the soil without having a negative impact on the yield and N content of the biomass. These results strongly advocate for the environmental benefits of BRs over chemical fertilizers and underline their suitability as biofertilizers and substitutes for chemical fertilizers in similar agricultural systems. Graphical abstract Unlabelled Image Highlights • Use of biogas residues as biofertilizers mitigates nitrate leaching risk. • Biomass yield and N uptake are similar for biogas residues and chemical fertilizers. • Partial substitution of synthetic N by biogas residues has environmental benefits. • Higher organic and synthetic N rate does not lead to higher agronomic performance. • Annual rainfall can affect the utilization and losses of plant available nitrogen. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Dry biorefining processing maximized water-soluble P and K recycling. • Recycling of lignin combustion ash significantly reduced use of P and K fertilizer. • MESP of cellulosic ethanol was reduced by 2.1–3.3%. Abstract Lignocellulose biorefinery produces fuel ethanol and lignin residue byproduct. The combustion ash of lignin residue after electricity generation contains high amount of phosphorous and potassium elements and the recycling to farmland provides a sustainable nutrients supply. This study demonstrated a maximum scenario of water- soluble phosphorous and potassium recycling through a dry biorefining process by reduction of wastewater generation to an extremely low level, in which the soluble phosphorus and potassium compounds were preserved. For biorefining one metric ton of five different lignocellulose biomass, averagely 51–87 kg of lignin combustion ash, 0.75–1.12 kg of phosphorous or equivalent 1.75–2.57 kg of P 2 O 5 , and 1.03–2.26 kg of potassium or equivalent 1.24–2.73 kg of K 2 O were obtained. The recycling of the ash to farmland covered 78–90% and 100% (with surplus) of the world average phosphate and potash fertilizer use, respectively. Even for the need of farmland in China with the heavily overused phosphate and potash fertilizers, the lignin combustion replaced 17–19% of phosphate fertilizer and 30–70% of potash fertilizer. The minimum ethanol selling price was also reduced by 2.1–3.3% by the fertilizer replacement. [ABSTRACT FROM AUTHOR]

Abstract Coral reefs are highly productive ecosystems that typically exist in nutrient-poor waters, stimulating considerable research on the sources of nutrients that may support this productivity, including nutrient recycling. We examined the potential for resident herbivorous damselfish (Stegastes nigricans) to recycle nutrients within their territories by conducting an exclusion experiment on S. nigricans territories and measuring algal turf growth on shallow fringing reefs in Mo'orea, French Polynesia. A nutrient bioassay was used to evaluate whether the enhanced growth was due to increased nutrients. We chose 15 isolated damselfish territories for a caging experiment, with a large cage obstructing all fish access on one half of the territory (−Damselfish, −Herbivory) and a small low-profile cage allowing access but not herbivory to a portion on the other half (+Damselfish −Herbivory). Additionally, we measured turf in a randomly-chosen uncaged area within each territory where both damselfish and herbivory were present (+Damselfish +Herbivory). Behavioral observations confirmed damselfish rarely swam over the large-caged half of the territory, effectively eliminating their physical presence, but continued to interact with the other half. Over the 16-day experiment, time and treatment had a significant effect on turf growth. By day 16, the turf receiving the +Damselfish −Herbivory treatment experienced average net turf growth of 5.34 mm, which was significantly greater than turf growth within the territories receiving the −Damselfish −Herbivory (2.13 mm) and the +Damselfish +Herbivory (1.50 mm) treatments. The macroalgae in the nutrient bioassay grew 21% more on the side of the territory where damselfish were present compared to the side where they were excluded, supporting our conclusion that the mechanism that supported faster turf growth was increased nutrients. Thus, our study was the first to establish experimentally that the presence of damselfish increased algal growth by enhancing nutrient supplies via recycled waste products, a mechanism that has been advanced but never tested. Surveys established that damselfish territories covered 28–64% of the fringing reef flat along the north shore of Mo'orea, suggesting this increased productivity within territories could be a significant contribution to total reef productivity. These findings highlight the importance of continuing research into the long-term and spatial-scale effects of damselfish as nutrient recyclers on coral reefs. Highlights • Algal turf grew more in the presence of damselfish than in their absence. • Nutrient bioassay demonstrated faster algal turf growth due to increased nutrients. • This nutrient supplement may be important as territories cover large areas of reef. [ABSTRACT FROM AUTHOR]

Abstract Increased aquaculture production will result in increased amounts of waste produced, and these wastes are highly underexploited. Polychaetes might effectively consume such waste and transfer them into compounds as marine proteins and lipids. In our study, growth and nutritional composition of the polychaete worm Hediste diversicolor (O.F. Müller, 1776) were analyzed to evaluate i) the capability of H. diversicolor to utilize waste from land-based salmon smolt farms for growth and ii) the nutritional composition of H. diversicolor cultivated on salmon smolt waste. The worms were fed iso‑carbonic diets comprised of fish feed, smolt waste, microalgae paste, and a 1:5 mixture (based on carbon content) of microalgae paste and smolt waste for a period of 30 days. H. diversicolor reared on fish feed grew significantly faster (wet weight basis) than worms grown on the other diets (SGR = 0.025 d−1). Worms fed with the mixture of smolt waste and microalgae showed the lowest growth (SGR = 0.003 d−1), while no significant differences were found between worms cultivated on smolt waste and microalgae paste (0.012 d−1 vs. 0.014 d−1, respectively). The lipid content in H. diversicolor ranged between 12 and 16% of DW for all treatments, whereof approximately 45% of the total fatty acids were comprised of polyunsaturated fatty acids (PUFA). Palmitic acid (C16:0) and eicosapentaenoic acid (C20:5 n -3; EPA) were found to be the most abundant fatty acids in the worms. Docosahexaenoic acid (C20:6 n -3; DHA) content increased significantly from 1.5% to 4.6–7.8% of the total fatty acids during the experiment for all treatments. The protein content ranged between 54 and 58% of DW, and the most abundant essential amino acids (EAA) were found to be lysine and leucine. We calculated that potential polychaete biomass produced via recycling smolt waste nutrients will account for 8% of smolt production, indicating that H. diversicolor can not only be successfully reared on waste sludge from land-based salmon smolt aquaculture, but they also contain high valuable compounds, and therefore can help to increase the protein and lipid availability meanwhile decreasing the environmental impact from aquaculture activities. Highlights • H. diversicolor can be reared on salmon smolt waste to increase sustainability in fish aquaculture • H. diversicolor contained high levels of compounds, such as proteins, lipids, etc., which can be developed as feed resources • The potential polychaete biomass produced via recycling smolt waste nutrients account for 8% of smolt production [ABSTRACT FROM AUTHOR]

Abstract Straw dead stock is a key driver for crop residue management decisions regarding bioenergy production. Therefore, a field study was conducted to evaluate the sugarcane straw decomposition under different straw removal rates, characterize straw composition changes, and quantify the straw-derived C and N loss. Four sugarcane straw removal rates were evaluated: no removal (14.0 Mg ha−1 of DM), 25 (10.5 Mg ha−1 of DM), 50 (7.0 Mg ha−1 of DM) and 75% (3.5 Mg ha−1 of DM) of straw removal. Our results showed that straw removal rate had no effect on first year of straw deposition, but during the second year, the lowest decomposition was associated with higher straw removal rates. Dry mass loss was also approximately 25% higher in the second year than in the first. Furthermore, carbon and nitrogen loss were two- and threefold higher in the first year compared to the second year of deposition. Overall, cellulose and hemicellulose decreased by 13 and 7%, respectively, while lignin increased proportionally by 92% during the two year experiment. Our findings suggest that the most appropriate removal rate to maintain soil quality and meet the demands for energy production is 50% of the total straw deposited on the soil. Highlights • We tracked the sugarcane straw decomposition over two years under Brazilian conditions. • The lowest decomposition was associated with higher straw removal rates. • Straw removal did not impact the relative C and N losses. • The effects of removal rates on straw C:N ratio was site-specific. • C:N ratio, cellulose and hemicellulose content would be important predictors of decomposition changes. [ABSTRACT FROM AUTHOR]

In the last decade substantial innovation in feeds has led to a significant reduction in fishmeal inclusion rates in feed for aquaculture. Nevertheless, to maintain the current growth of aquaculture, the demand of nutrient will increase at the same rate. So finding a sustainable alternative protein source to replace fish meal in fish feed continues being an important issue to supply the growing market demand of aquaculture products. This study has been conducted to examine the feasibility of partially replacing fishmeal in feed for rainbow trout, for a sustainable algal biomass obtained from the pig manure treatment. The biomass obtained was mainly composed by Scenedesmus almeriensis with a nutritional composition of 46.7% of protein and 4.1% of fat, and was included in feed for rainbow trout at increasing levels of replacement of the fishmeal: 0 (control), 5%, 10%, 20% and 40%. The feeding trial was performed for 82 days in trout with an initial weight of ~75 g. The effect of the replacement level of the fishmeal in diets was evaluated on growth performance, protein utilization, fish health, biosecurity of the products, and on the quality of final product. Trout fed with diet containing microalgal biomass showed a lower growth, but within normal values for trout in that growing period. Regarding the rest of parameters, non-negative effects on the health, on biosecurity and on the final quality product were observed. This study highlights the novel strategy of using microalgae as nexus between pig manure-nutrient-food to nutrient recycling, and opens a wide range of possibilities to obtain a sustainable protein source for aquaculture. [ABSTRACT FROM AUTHOR]

Highlights • Mineralization of nutrient-rich sludge constitutes a solution for aquaculture waste treatment. • UASB reactors can break down sludge into bioavailable nutrients, which can be delivered to plants. • Results indicate that UASB reactors operating at low pH can contribute towards nutrient-recovery. Abstract There is a recognized need for mineralizing aquaculture-derived sludge in aquaponics systems in order to reduce waste production. Many recent studies of aquacultural waste treatment have focused only the production of biogas as opposed to the potential for mineralization of nutrient-rich sludge. Upflow anaerobic sludge blanket (UASB) reactors provide one possible solution for breaking down sludge into bioavailable nutrients that can subsequently be delivered to plants. As such, this study examines the mineralization performance of sequential UASB reactors that are designed with an expanded granular sludge bed (EGSB) and compared to standard aerobic and anaerobic batch reactors. Results of our experiments demonstrate that only chemical oxygen demand reduction is significantly different. An unexpected drop in pH of one of the three reactor systems revealed that a pH below 6 was able to significantly increase the mineralization and mobilization of nutrients. Approximately 25% of phosphorus, potassium, and calcium could also be recovered from the sludge under lower pH conditions, as compared to the mineralization performance of standard UASB reactors running at a higher pH. However, the opposite effect was observed with respect to organic sludge reduction, where diminished performance was observed in the low-pH reactor. The current study implies that anaerobic reactors operating at low pH can potentially contribute towards improved nutrient recovery in multi-loop aquaponics systems and reduction of additive agents for pH control of the hydroponic subsystem. [ABSTRACT FROM AUTHOR]

The intensive agricultural practices are increasing the demand for chemical fertilizers, being currently produced from a non-environmental friendly way. Besides the environmental impacts, the nutrient uptake efficiency by the crops is very low, representing huge losses into the fields. Therefore, it is crucial to study alternatives for the current chemical fertilizers, which simultaneous improve nutrient efficiency and minimize environmental impacts. A sustainable solution is to recover nutrients from wastewater streams with microalgal cultures and the biomass conversion into bio-char for soil amendment. Wastewaters are loaded with nitrogen and phosphorus and can be used as culture medium for microalgae. Thus, nutrients can be recycled, reducing the requirement of chemical fertilizers. This paper aims to review nutrient recovery from wastewater using microalgae and the biomass conversion into bio-char. This process promotes nutrient recycling and the bio-char (when added to soil) improves the nutrient uptake efficiency by crops. [ABSTRACT FROM AUTHOR]

Managing organic waste streams is a major challenge for the agricultural industry. Anaerobic digestion (AD) of organic wastes is a preferred option in the waste management hierarchy, as this process can generate renewable energy, reduce emissions from waste storage, and produce fertiliser material. However, Nitrate Vulnerable Zone legislation and seasonal restrictions can limit the use of digestate on agricultural land. In this paper we demonstrate the potential of cultivating microalgae on digestate as a feedstock, either directly after dilution, or indirectly from effluent remaining after biofertiliser extraction. Resultant microalgal biomass can then be used to produce livestock feed, biofuel or for higher value bio-products. The approach could mitigate for possible regional excesses, and substitute conventional high-impact products with bio-resources, enhancing sustainability within a circular economy. Recycling nutrients from digestate with algal technology is at an early stage. We present and discuss challenges and opportunities associated with developing this new technology. [ABSTRACT FROM AUTHOR]

European agriculture is a large importer of nutrients in the form of chemical fertilizers. Additionally, countries with livestock-intensive farming face problems with disposal of nutrients in animal manure. The availability of chemical fertilizers has changed farmers' past dependence on manure. Nowadays, despite its nutrient content, manure is sometimes considered as a waste product. However, if the characteristics of manure and other waste streams could be enhanced through processing, it could be transformed into an alternative bio-based fertilizer recycling the nutrients within the farming sector. This would also create opportunities for nutrient exchange between different European regions. However, a key question is what is needed for farmers to accept these products as replacements for their current chemical fertilizer use? In this paper, key attributes determining the acceptance of alternative bio-based fertilizer products are identified. Based on the identified attributes, a discrete choice experiment was designed to reveal farmers' preferences and Willingness-To-Pay for these attributes. Identical experiments were conducted in seven different European countries. The results indicate that farmers from the different countries have common preferences for concentrated products that have certainty in the nitrogen content and at a lower price than chemical fertilizer. Other attributes such as the presence of organic carbon, hygienization of the product and fast release of nutrients were only statistically significant in some countries. The results imply that a bio-based fertilizer similar to chemical fertilizers could be sold at around 65% of the price of mineral fertilizer. Additionally, we show which attributes industry should take into consideration when estimating the demand for new bio-based fertilizer products. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is an established technology to produce renewable energy as methane-rich biogas for which microalgae are a suitable substrate. Besides biogas production, anaerobic digestion of microalgae generates an effluent rich in nutrients, so-called digestate, that can be used as a growth medium for microalgal cultures, with the potential for a closed nutrient loop and sustainable bioenergy facility. In this study, the methane potential and nutrient mobilization of the microalga Scenedemus dimorphus was evaluated under continuous conditions. The suitability of using the digestate as culture medium was also evaluated. The results show that S. dimorphus is a suitable substrate for anaerobic digestion with an average methane yield of 199 mL g −1 VS. The low level of phosphorus in digestate did not limit algae growth when used as culture medium. The potential of liquid digestate as a superior culture medium rather than inorganic medium was demonstrated. [ABSTRACT FROM AUTHOR]

Autophagy is a highly conserved pathway in eukaryotes that promotes nutrient recycling and cellular homeostasis through the degradation of excess or damaged cytoplasmic constituents. In plants, autophagy is increasingly recognized as a key contributor to development, reproduction, metabolism, leaf senescence, endosperm and grain development, pathogen defense, and tolerance to abiotic and biotic stresses. Characterizing the functional transcriptomic, proteomic, and metabolomic networks relating to autophagy in plants subjected to various extra- and intra-cellular stimuli may help to identify components associated with the pathway. As such, the integration of multi-omics approaches (i.e., transcriptomics, proteomics and metabolomics), along with cellular, genetic and functional analyses, could provide a global perspective regarding the effects of autophagy on plant metabolism, development and stress responses. In this mini-review, recent research progress in plant autophagy is discussed, highlighting the importance of high-throughput omics approaches for defining the underpinning molecular mechanisms of autophagy and understanding its associated regulatory network. [ABSTRACT FROM AUTHOR]

This paper aims to develop a generic roadmap for setting up strategies for nutrient recovery from digested waste (digestate). First, a guideline-based decision-tree is presented for setting up an optimal bio-based fertilization strategy as function of local agronomic and regulatory criteria. Next, guidelines and evaluation criteria are provided to determine the feasibility of bio-based fertilizer production as function of the input digestate characteristics. Finally, a conceptual decision making algorithm is developed aiming at the configuration and optimization of nutrient recovery treatment trains. Important input digestate characteristics to measure, and essential factors for monitoring and control are identified. As such, this paper provides a useful decision-support guide for wastewater and residuals processing utilities aiming to implement nutrient recovery strategies. This, in turn, may stimulate and hasten the global transition from wastewater treatment plants to water resource recovery facilities. On top of that, the proposed roadmap may help adjusting the choice of nutrient recovery strategies to local fertilizer markets, thereby speeding up the transition from a fossil-reserve based to a bio-based circular nutrient economy. [ABSTRACT FROM AUTHOR]

In this study, nutrient properties and carbon sequestration potential of biochars derived from chicken manure (CM) impregnated with mineral salts (calcium chloride, magnesium chloride, ferric chloride) were evaluated. Pretreatment with mineral salts reduced phosphorus (P) availability via the formation of insoluble metal phosphate minerals. Less carbon was lost during the pyrolysis of pretreated CM, and the produced biochars (BC Ca , BC Mg , and BC Fe ) were more stable (i.e., reduced C loss during chemical oxidation and less CO 2 release during incubation) than pristine biochars. Spectroscopic evidence indicated that enhanced biochar stability via metal salt pretreatment before pyrolysis was related to increased aromatization and enhanced physical protection due to the metal-oxygen interaction, together with the formation of metal mineral phases on biochar surfaces. Moreover, ferric chloride was the optimal additive, as it significantly decreased biochar P leachability and increased carbon sequestration potential. [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]

Anaerobic digestion of food waste within urban areas can generate decentralised renewable energy and support community enterprise activities, thereby contributing to closing the waste-energy-food loop. However, widespread uptake of small-scale, urban anaerobic digestion networks is limited by economic costs and the safe disposal of surplus digestate. This paper uses an interdisciplinary approach to assess the feasibility of anaerobic digestate management through the installation of hydroponics or algae cultivation systems, based on a case study of a micro anaerobic digestion system in London, England. Results show that installing a dewatering sifter together with a hydroponics system is a technically and economically feasible option for digestate enhancement in the urban environment. Its installation is, however, not currently justified for the system under consideration due to cost, regulatory, spatial, and contextual constraints identified using actor-network analysis. Nevertheless, if regulatory and wider contextual issues are accommodated, and more than 30 L of digestate are produced daily, a dewatering and vertical hydroponic system could result in a profit of approximately £100,000 over 10 years. While the microalgal system was also able to upgrade digestate, at present productivity is too low and the capital cost of photobioreactor technology is prohibitively expensive. This underlines the need for technical improvements and low-cost enhancement options to achieve justifiable paybacks until regulatory reforms and the wider economic situation are more favourable to anaerobic digestion treatment within cities. [ABSTRACT FROM AUTHOR]

Leaf litter mixtures and the amount of litter biomass in the litter standing stocks can affect the decomposition rates by modifying physical properties and resource heterogeneity in the litter layers. However, the potential interactive effects of litter mixtures and the amount of litter biomass on decomposition have been overlooked in the literature, even though both aspects of litter layer may be highly variable in space and time, within and across ecosystems. In a field experiment conducted in a seasonally dry tropical forest (also known as restinga forest), we investigated the individual and interactive effects of litter mixing and litter biomass on the decomposition of leaf litter from four species of trees, at both species- and assemblage-level. We hypothesized that the mixing of litter and higher litter biomass would both promote litter decomposition, and that litter mixture effects on decomposition at assemblage- and species specific-level would be stronger under higher litter biomass. Mixing of litter and the amount of litter in the standing stocks had no significant individual effects on decomposition, neither at the assemblage- or species specific-level. However, we observed an interactive effect between both experimental factors for the decomposition of a single species, where, contrary to our predictions, the decomposition of Andira legalis at low litter biomass was slightly reduced in the litter mixture. Our results indicate that litter decomposition in the restinga ecosystem should be highly predictable with knowledge of species composition and species-specific decomposition rates, and suggest that, at least for seasonally dry tropical ecosystems, the mixing of litter may have only a small effect on the decomposition process. [ABSTRACT FROM AUTHOR]