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Insect protein production is considered a sustainable alternative to livestock protein which furthermore utilizes waste streams. Its production can have positive but also potentially negative environmental effects, which require evaluation. Frass, the byproduct of insect production, is regarded an efficient organic fertilizer or soil amendment. However, several studies report negative frass effects on plant growth and nitrogen (N) cycling. Therefore, a pot trial was carried out which sought to understand N release from frass and subsequent growth and nutrient uptake of Italian ryegrass. Mealworm frass (MWF) or buffalo worm frass (BFW) was applied at two rates (1.5 and 3% w/w) to a soil-sand mix. To evaluate N release processes, frass was applied alone, with a nitrification inhibitor (NI), a urease inhibitor (UI), or both (NI+UI). Plant N, nutrient uptake and soil inorganic N were measured at the experiment's end. To gauge whether altered N fluxes induced changes in the microbial community, soil microbial biomass, bacterial/archaeal abundances and ergosterol content as a fungal biomarker, were determined. Both frass types and application rates stimulated microbial growth and N mineralization. The 3% rate inhibited seed germination, possibly due to salinity or ammonia toxicity. At the 1.5% rate, both frass types were effective fertilizers. MWF led to higher biomass and nutrient uptake, owing to its higher extractable nutrient concentrations. The 3% rate caused nitrite accumulation in the absence of NI. NI improved plant biomass, nutrient uptake, stimulated archaeal and bacterial abundances and prevented nitrite accumulation. UI reduced N mineralization, showing that a substantial fraction of frass organic N is ureic. UI enhanced fungal contribution to the microbial biomass, revealing the importance of bacteria in frass N mineralization processes when UI is not applied. NI and UI combined, induced greater N release from frass than UI or NI alone. Our study demonstrated the usefulness of NI and UI in studying N release from frass. NI can improve plant N uptake and minimize N losses following frass application, reducing its potentially negative effects. UI can retard N release from frass, allowing its application as a slow-release fertilizer, but should not be used concurrently with NI.

The use of liquid waste as a feedstock for cultivation of microalgae can reduce water and nutrient costs and can also be used to treat wastewater with simultaneous production of biomass and valuable products. This study applied strategies to treat diluted anaerobic digester effluent (ADE) as a residue of biogas reactors with moderate (87 ± 0.6 mg L−1; 10% ADE) and elevated NH4+-N levels (175 ± 1.1 mg L−1; 20% ADE). The effect of ADE dilution on the acclimatization of various microalgae was studied based on the analysis of the growth and productivity of the tested green algae. Two species of the genus Chlorella showed robust growth in the 10–20% ADE (with a maximum total weight of 3.26 ± 0.18 g L−1 for C. vulgaris and 2.81 ± 0.10 g L−1 for C. sorokiniana). The use of 10% ADE made it possible to cultivate the strains of the family Scenedesmaceae more effectively than the use of 20% ADE. The growth of Neochloris sp. in ADE was the lowest compared to other microalgal strains. The results of this study demonstrated the feasibility of introducing individual green microalgae into the processes of nutrient recovery from ADE to obtain biomass with a high protein content.

A stochastic nutrient–phytoplankton–zooplankton model with instantaneous nutrient recycling is proposed and analyzed in this paper. When the nutrient uptake function and the grazing function are linear and the ingested phytoplankton is completely absorbed by the zooplankton, we establish two stochastic thresholds R0S and R1S, which completely determine the persistence and extinction of the plankton. That is, if R0S<1, both the phytoplankton and the zooplankton eventually are eliminated; if R0S>1 and R1S<1, the phytoplankton is persistent in mean but the zooplankton is extinct; while for R1S>1, the entire system is persistent in mean. Furthermore, sufficient criteria for the existence of ergodic stationary distribution of the model are obtained and the persistent levels of the plankton are estimated. Numeric simulations are carried out to illustrate the theoretical results and to conclude our study. Our results suggest that environmental noise may cause the local bloom of phytoplankton, which surprisingly can be used to explain the formation of algal blooms to some extent. Moreover, we find that the nonlinear nutrient uptake function and grazing function may take credit for the periodic succession of blooms regardless of whether they are in the absence or presence of the environmental noises.

The staggering production of rock dusts and quarry by-products of mining activities poses an immense environmental burden that warrants research for value-added recycling of these rock mineral powders (RMP). In this study, an incubation experiment was conducted to determine potassium (K) and micronutrients (Zn, Cu, Fe and Mn) release from a quarry RMP to support plant nutrition. Four different size fractions of the RMP were incubated with organic amendments (cow dung and legume straw) under controlled conditions for 90 days. Samples were collected at different intervals (7, 15, 30, 45, 60 and 90 days) for the analysis of available K and micronutrients in the mineral-OM mixtures and leachates. There was a significant (p <0.05) increase in pH of leachates from the mineral-OM mixtures. The K release was significantly higher from the finer size fraction of RMP. About 18.7% Zn added as RMP was released during the incubation period. Zn release increased from 4.7 to 23.2% as the particle size of RMP decreased. Similarly, Cu release from RMP increased from 2.9 to 21.6%, with a decrease in the particle size. Fe and Mn recovery from RMP recorded 11.2 and 6.6%, respectively. Combined application of OM and RMP showed significantly higher nutrient release than other treatments. This study indicates that effective blending of RMP with organic amendments could be a potential source of K and micronutrients in agriculture without posing a risk of toxic element contamination to the soil. [ABSTRACT FROM AUTHOR]

The objective of this study was to verify the feasibility of using biochar, functionalized with layered double hydroxides, as a fertilizer after its use in phosphate treatment (P-BC-LDHs). It was conducted with several levels of P-BC-LDHs using seed germination and early growth assays of lettuce (Lactuca sativa L.). The application of P-BC-LDHs resulted in successful seedling emergence, with an excellent germination capacity of over 96% for all treatments. However, compared to the controls, P-BC-LDHs did not provide favorable seedling traits. In contrast, in the latter experiments, lettuce cultivated under mixtures with P-BC-LDHs, particularly at an application rate of 2.5% (w/w), displayed superior growth quality to those under non-treated conditions. The length of lettuce shoots and roots from this optimal dosage were increased by at least 24% compared to untreated samples. A 17% reduction in biomass yield was observed for the samples from non-supplemented substrates. The nutrient release profiles showed that P-BC-LDHs were capable of slowly supplying phosphorus, thereby increasing the long-term nutrient availability for plants. The findings reported here provide important insights into these materials and confirm that P-BC-LDHs can be used for agricultural purposes after phosphate remediation applications. The results of this study provide constructive information to facilitate the implementation of biochar-based LDH composites for sustainable phosphate removal and recovery. [ABSTRACT FROM AUTHOR]

The circular economy (CE) is currently generating considerable expectations. The concept describes an aspired future but does not provide clear guidance for policy-making. As policy outcomes often rest on initiatives generated in a bottom-up fashion, our attention must be directed to the ways policies are made accessible and interesting to those who might take the initiative. We claim that on-line publicity plays a key role in this. Our findings from a hyperlink analysis focusing on a government funding call for nutrient recycling in Finland show how multiple versions of the policy topic unfold online, as emergent hyperlink clusters prioritize specific agents, material circuits, and policy visions over others. The topic becomes connected with activities and agendas to create path dependencies and to strengthen existing divisions rather than to advocate change. Thus, we argue that CE policy design must recognize the way policy is shaped through online publicity creation. [ABSTRACT FROM AUTHOR]

Biochar is increasingly being applied as a soil amendment in agriculture. Biochar is typically produced from plant biomass and contains relatively low amounts of plant nutrients (e.g., N, P, and K), thus providing limited fertilizer value. Human excreta contains plant nutrients that could be recycled to create sustainable agricultural nutrient cycles. This study investigated the potential of biochar derived from a dry toilet substrate as soil amendment. The substrate consisted of urine, faeces, and wood chips, and was pyrolyzed at 500–650 °C for 10 min. The biochar was analyzed for plant available P, water leachable P and K, carbon stability, pH, electrical conductivity, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dioxins, and germination tests with barley and lettuce were conducted to estimate the biochar fertilizer value and potential bio-toxicity. The biochar contained 25.0 ± 1.0 g N/kg dry mass (DM), 33.1 ± 2.1 g P/kg DM and 20.7 ± 0.2 g K/kg DM. 65% DM P was extractable by formic acid solution, 31.7% DM P and 60.5% DM K were water leachable in a ten-day column water-leaching experiment. The biochar complied with European regulations for PAHs, PCBs, dioxins and heavy metal concentrations, except for Zn and Ni. Germination of salt-resistant barley was not affected by biochar doses < 50% DM, while salt-sensitive lettuce germination was inhibited at doses ≥ 2% DM, indicating that the dry toilet substrate biochar induced salt stress. Based on these results, it is recommended that urine separation should be considered for biochar of excreta, which could reduce salt stress while maintaining concentrations of "fixed" or bioavailable nitrogen. [ABSTRACT FROM AUTHOR]

In the Amazonian periphery, there are sources of numerous disservices, including deforestation, loss of wildlife habitat and biodiversity erosion. However, there are great opportunities to adopt appropriate agricultural management practices to take advantage of the benefits of ecosystem services for sustainable agricultural intensification. Thus, the aim of this work was to evaluate the effects of certain ecosystem services provided by combined use of legumes with residue of low- and high-quality on soil quality indicators, nitrogen use efficiency and sustainability of maize grain yield in infertile tropical soil. The overarching objective is to determine how ecosystem services can contribute to the improvement of land-use policy to ensure the sustainability of cultivated lands, in such a way that forest can be preserved by avoiding deforestation of other new areas through shifting cultivation systems. Four leguminous tree species were used, two with high-quality residues Leucaena leucocephala (leucaena) and Gliricidia sepium (gliricidia) and two with low-quality residues Clitoria fairchildiana (clitoria) and Acacia mangium (acacia). Maize grain yield was evaluated between 2011 and 2017 in these treatments. In 2018, to assess how ecosystem services affect crop performance, the treatments were divided into ten treatments with and without urea. We conclude that increased uptake of inorganic and organic N by maize resulting from improvement of the soil quality indicators may allow agricultural intensification. This improvement can help meet the challenges of sustainability and feasibility of agroecosystems of the Amazonian periphery by making the agroecosystem more productive year by year. Therefore, our results confirm that the utilization of an ecosystem services style approach can help meet the challenges of sustainability and feasibility in agrosystems of the Amazonian periphery. In addition, these results can contribute to the development of land-use policy in the Amazonian periphery, aiming for the intensification of agriculture in cropped areas to avoid deforestation of new areas from shifting cultivation systems.

Sustainability assessments can be a powerful tool in decision-making regarding technical innovations. In this study, a sustainability assessment of technical systems for recovering nutrients and carbon from domestic wastewater is presented. Multi-criteria analysis was used to calculate a sustainability score of three different technical systems compared to a baseline in two case-studies: the Fyriså river catchment in Sweden and the Słupia river catchment in Poland. Two participatory workshops with local stakeholders were held in each case-study, the first to co-develop the system alternatives and sustainability criteria and the second to collect stakeholder weighting of the criteria. Although the systems assessed in both case studies were similar, the resulting sustainability scores were different. In Fyris, although the differences in scores was small, the preferred alternative was introduction of source-separation followed by a large redesign of the treatment and phosphorus extraction from incinerated sludge was the least sustainable alternative. For the Słupia systems the scores varied more, and the preferred system was a large redesign of the wastewater treatment followed by ammonia stripping of the reject water and the source-separation alternative received the lowest score. In both case-studies, the more costly system received highest sustainability score indicating the large potential benefits of enhancing resource recovery from domestic wastewater. Stakeholders did not prioritize technical aspects over the other sustainability criteria, yet most of research on resource recovery interventions is focused on technical performance.

In regions with intensive agricultural production, large amounts of organic waste are produced by livestock animals. Liquid digestate from manure-based biogas production could potentially serve as fertilizer if integrated with closed horticultural irrigation systems. The aim of this experiment was to investigate how fertilizer based on liquid biogas by-products of pig manure digestion can affect the growth and production of tomato plants. Integration of a nitrification bioreactor presumes a significantly lower concentration of nutrient solutions and a higher level of oxygenation than classical mineral cultivation. Therefore, additional controls were included. We compared plant growth and fruit quality traits of tomato plants grown in a hydroponic solution with organic fertilizer with two levels of mineral fertilizer. The tomatoes grown with organic waste-based liquid fertilizer showed reduced growth rates but increased mean fruit size, resulting in no significant change in total yield compared with high-mineral cultivation. The growth rate was similarly reduced in plants cultivated with low-mineral fertilizer. Plants cultivated with organic waste-based fertilizer had high Cl− concentration in xylem sap, leaves, and, ultimately, fruits. The leaves of plants cultivated with organic waste-based fertilizer contained higher concentrations of starch and soluble carbohydrate and low concentrations of phosphorous (P) and sulfur (S). The plants grown with organic waste-based or low-mineral medium showed significantly poorer fruit quality than the plants cultivated with the high-mineral solution. The low-mineral treatment increased xylem sap contribution to fruit weight because of higher root power. The organic waste-based fertilization did not change the root power but increased fruit size. In conclusion, organic waste-based cultivation is a possible solution for sustainable plant production in greenhouses. However, additional adjustment of nutrient supply is required to improve fruit quality.

In regions with intensive agricultural production, large amounts of organic waste are produced by livestock animals. Liquid digestate from manure-based biogas production could potentially serve as fertilizer if integrated with closed horticultural irrigation systems. The aim of this experiment was to investigate how fertilizer based on liquid biogas by-products of pig manure digestion can affect the growth and production of tomato plants. Integration of a nitrification bioreactor presumes a significantly lower concentration of nutrient solutions and a higher level of oxygenation than classical mineral cultivation. Therefore, additional controls were included. We compared plant growth and fruit quality traits of tomato plants grown in a hydroponic solution with organic fertilizer with two levels of mineral fertilizer. The tomatoes grown with organic waste-based liquid fertilizer showed reduced growth rates but increased mean fruit size, resulting in no significant change in total yield compared with high-mineral cultivation. The growth rate was similarly reduced in plants cultivated with low-mineral fertilizer. Plants cultivated with organic waste-based fertilizer had high Cl− concentration in xylem sap, leaves, and, ultimately, fruits. The leaves of plants cultivated with organic waste-based fertilizer contained higher concentrations of starch and soluble carbohydrate and low concentrations of phosphorous (P) and sulfur (S). The plants grown with organic waste-based or low-mineral medium showed significantly poorer fruit quality than the plants cultivated with the high-mineral solution. The low-mineral treatment increased xylem sap contribution to fruit weight because of higher root power. The organic waste-based fertilization did not change the root power but increased fruit size. In conclusion, organic waste-based cultivation is a possible solution for sustainable plant production in greenhouses. However, additional adjustment of nutrient supply is required to improve fruit quality. [ABSTRACT FROM AUTHOR]

An electrical conductivity (EC)-based closed-loop soilless culture system is practical for in-field deployment. Literature on the closed-loop soilless culture nutrient management premise the limitations in managing recycled nutrients under dynamic changes in individual nutrient uptake concentrations. However, recent systems analysis studies predicting solutions for nutrient fluctuation stabilization in EC-based closed-loop soilless culture systems suggest that the system may have a deterministic side in nutrient variation. This study aims to derive a nutrient control principle in an EC-based nutrient recycling soilless culture system by theoretical and experimental analyses. An integrated model of solutes such as K+, Ca2+, and Mg2+ and water transport in growing media, automated nutrient solution preparation, and nutrient uptake was designed. In the simulation, the intrinsic characteristics of nutrient changes among open-, semi- closed-, and closed-loop soilless cultures were compared, and stochastic simulations for nutrient control were performed in the closed-loop system. Four automated irrigation modules for comparing nutrient changes among the soilless culture systems were constructed in the greenhouse. Sweet pepper plants were used in the experiment. In the experimental analysis, nutrient concentration conversion to the proportion between nutrients revealed distinctive trends of nutrient changes according to the treatment level of drainage recycling. Theoretical and experimental analyses exhibited that nutrient variations in open-, semi- closed-, and closed-loop soilless culture systems can be integrated as a function of nutrient supply to the system's boundary areas. Furthermore, stochastic simulation analysis indicated that the nutrient ratio in the soilless culture system reveals the nutrient uptake parameter-based deterministic patterns. Thus, the nutrient ratio in the closed-loop soilless culture could be controlled by the long-term feedback of this ratio. We expect that these findings provide theoretical frameworks for systemizing nutrient management techniques in EC-based closed-loop soilless culture systems. [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]

One strategy to re-use solid urban wastes is the production of energy by anaerobic digestion. This process also generates high volume of digestates, which are frequently disposal in landfills. The aim of this work is to assess anaerobic digestates as agricultural inputs. Three different biomethanation wastes from different plants were collected. Firstly, a complete physico-chemical characterization of the wastes was done according to the Spanish regulation, showing that the materials had the 90% of the particles below 25 mm, high values of pH, electric conductivity, organic matter, humic acids and soluble nutrients such as NO3−, SO42−, Ca2+, Mg2+, PO43− and K+. Total concentrations of heavy metals and microbiological parameters were below the threshold levels allowed for agricultural use. The wastes were then treated with a strong acid and a strong base having two different solutions (ATr and BTr, respectively) which were evaluated as biostimulants for tomato plants in hydroponic culture. Those liquid extracts, ATr and BTr, demonstrated their biostimulant ability towards root system of tomato enhancing the hair root density and plant biometric parameters including plants weight and chlorophyll content. This work demonstrates the re-use feasibility of treated digestates in agriculture as fertilizers and more over as feedstock for biostimulants production. [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]

Sewage sludge management for fertilizer purposes can be a step in the circular phosphorus (P) economy. Using microbial solubilization in manufacturing fertilizers from recycled materials is an innovative approach with the potential to increase P compounds’ bioavailability, and fertilizers from sewage sludge ash and P-solubilizing bacteria are promising products of this technology. In addition to P and a range of macronutrients, these fertilizers contain small amounts of micronutrients and potentially toxic elements. This paper discusses the effects of fertilizer on iron (Fe) and aluminum (Al) content in soil, test plants (spring or winter wheat; grain and straw), weeds and post-harvest residues, based on field experiments. Treatments with conventional P fertilizers (superphosphate, phosphorite) and without P fertilization provided references. The tested biofertilizers containing the Bacillus megaterium or Acidithiobacillus ferrooxidans strain had no effect on total Fe and Al content in the soil or on the concentration of these elements in plant biomass when applied at P doses up to 35.2 kg ha–1. Fe and Al levels in grain did not suggest a potential risk to consumers.

Cities consume the majority of proteins produced globally but have unsustainable, linear food systems from production to consumption to disposal, resulting in significant nutrient losses. The industrial rearing of insects is a promising strategy for converting otherwise lost nutrients back into protein-rich animal feed and fertilizer, particularly to supplement local food production. The black soldier fly (BSF), Hermetia illucens, has been identified as a candidate for industrial rearing. BSF has a superior feed conversion ratio and cycle-time compared to other edible insects and can convert and recover nutrients from a vast variety of organic materials to protein, oil and chitin making it an attractive solution for the management of urban organic solid waste. With an increasing awareness of the environmental urgency and interest in the economic potential of the technology, this review discusses the technological factors confounding the upscaling of insect farming in urban and peri-urban contexts using BSF as a case study. These include the challenges of feed homogenisation and pre-treatment, of integrating insect life-cycle factors (e.g. mating) with bioprocess engineering concepts (which complicates automation), of meeting the nutritional requirements of the larvae at different stages of growth in order to maximize bioconversion and product quality, and of elucidating the impact of microbiome on complex behaviours and bioconversion. A multidisciplinary effort is therefore required to lead urban insect farming to full development to ultimately contribute to future food security.

Nickel, a micronutrient essential for plant growth and development, has been recognized as a metallic pollutant in wastewater. The concentration of nickel ions in the water course, exceeding the maximum tolerable limit, has called for an alarming attention, due to the bioaccumulative entry in the water–plant–human food chain, leaving a burden of deteriorative effects on visible characteristics, physiological processes, and oxidative stress response in plants. In this work, the renewable utilization of nickel electroplating industrial wastewater effluent (0, 5, 10, 25, 50, and 100%) as a viable source of irrigation water was evaluated using a hydroponic cultivation system, by adopting Lablab purpureus and Brassica chinensis as the plant models, in relation to the physical growth, physiological and morphological characteristics, photosynthetic pigments, proline, and oxidative responses. The elongation of roots and shoots in L. purpureus and B. chinensis was significantly inhibited beyond 25 and 5% of industrial wastewater. The chlorophyll-a, chlorophyll-b, total chlorophyll, and carotenoid contents, accompanied by alterations in the morphologies of xylem, phloem, and distortion of stomata, were recorded in the industrial wastewater-irrigated groups, with pronounced toxicity effects detected in B. chinensis. Excessive proline accumulation was recorded in the treated plant models. Ascorbate peroxidase (APX), guaiacol peroxidase (POD), and catalase (CAT) scavenging activities were drastically altered, with a profound upregulation effect in the POD activity in L. purpureus and both POD and APX in B. chinensis, predicting the nickel-induced oxidative stress. Conclusively, the diluted industrial wastewater effluent up to the optimum concentrations of 5 and 25%, respectively, could be feasibly reused as a renewable resource for B. chinensis and L. purpureus irrigation, verified by the minimal or negligible phytotoxic implications in the plant models. The current findings have shed light on the interruption of nickel-contaminated industrial wastewater effluent irrigation practice on the physical and biochemical features of food crops and highlighted the possibility of nutrient recycling via wastewater reuse in a sustainable soilless cultivation.

This paper redefined the agricultural production system and its subsystems with respect to phosphorus (P) flow to improve the assessment of the phosphorus use efficiency (PUE), which is a key indicator for P security and sustainability of water resources. It also assessed the key P inflows, outflows, and PUE in the crop-pasture subsystem, livestock subsystem and the overall agricultural production system to present a comparative picture for these systems across various nations. PUE in the overall agricultural production system (averaged as 46% for the selected thirteen nations) is lower compared to the crop-pasture subsystem (averaged as 72%) but is higher than the livestock subsystem (averaged as 18%). Nations with high PUE in the crop-pasture subsystems usually showed high PUE in the overall agricultural production system. The proportional contribution of the livestock subsystem to the PUE of the overall agricultural production system is substantially higher than the crop-pasture subsystem for a number of EU countries (e.g., Netherlands (85%), Norway (84%), Switzerland (80%)), while the contribution of the crop-pasture subsystem is higher for some Asian countries (e.g., Bangladesh (93%) and India (87%)) and USA (80%). This study indicates that there is a high potential for improving PUE in the agricultural production system of Asian countries particularly through diverting manure-bound P from non-agricultural land or unproductive use to agricultural lands. This study suggests that shifting more towards crop production for plant-based food from animal feed/pasture production for animal-based food (meat) could improve PUE in the agricultural production system. Knowledge gaps identified and limitations addressed in this study could be useful for improving future national scale substance flow analyses (SFAs) of P for the better assessment of P flow and PUE in the agricultural production system.

Viruses are key players in the marine ecosystem. It is critical to study specific viral processes and their inter-relationship with various biotic and abiotic variables to quantify their impact on the marine environment. This study investigates the influence of seasonality on viral distribution and their mediated processes in the coastal region of the southeastern Arabian Sea (India) for two consecutive years (2014 and 2015). Water samples were collected from four sampling stations, S1, S2, S3 and S4, in the southeastern Arabian Sea on a monthly basis. Samples were analyzed for the variations in viral abundance, viral production, and viral-induced host mortality covering three seasons namely, pre-monsoon, monsoon and post-monsoon. Viruses and bacteria were enumerated by epifluorescence microscopy following staining with SYBR Green I and viral production was estimated using viral dilution method. Seasonal variations in viral-mediated mortality and microzooplankton grazing mortality of phytoplankton hosts were estimated by modified dilution method. The results revealed a pronounced seasonal pattern of viral abundance (0.04–4.03 × 107 viruses mL−1) and viral production (0.71 × 1010–4.94 × 1010 L−1d−1). The observed high viral-induced mortality of prokaryotes (25.85%) and phytoplankton (7.98–28.9%) during the pre-monsoon season was eventually linked to high viral abundance and production rates. Viral-mediated processes were essentially linked to host density and water temperature. Transmission electron microscopy analysis revealed that myoviruses and non-tailed viruses were dominant in the study region with rod-shaped bacteria being more susceptible to viral infection. The results indicated the prevalence of seasonally induced active viral processes in this tropical marine ecosystem which may significantly contribute to rapid recycling of nutrients in this region. [ABSTRACT FROM AUTHOR]

Anuran larvae can form the largest animal biomass seasonally in freshwater environments, yet, they are still one of the least-studied taxa in terms of nutrient regeneration. The present study tested whether sympatric tadpoles regenerate nutrients at similar rates and ratios, and whether increased intraspecific competition (hereafter 'competition') alters patterns of excretion. We quantified rates and ratios of excretion (dissolved nitrogen (N) from ammonia, phosphorus (P) from total dissolved P, and N : P ratio) in three pond-dwelling Japanese tadpoles (Pelophylax nigromaculatus , Rhacophorus schlegelii , Hyla japonica), and tested the effect of competition on excretion in Pelophylax nigromaculatus and Rhacophorus arboreus. The three co-occurring species regenerated nutrients at different rates and ratios; H. japonica excreted nutrients and produced faecal pellets at the lowest rates. Inside field enclosures, increasing tadpole density reduced the quantity but not the quality of excretion by the tadpoles, suggesting higher nutrient sequestration, likely to maintain a stoichiometrically balanced growth under limited resources. Differences in rates and ratios of excretion have previously been shown to have various effects on community structure by affecting primary productivity, highlighting the importance of species identity and interactions on ecosystem function. Anuran larvae can seasonally represent the largest animal biomass in freshwater environments, yet are still one of the least studied taxa in terms of nutrient recycling. The present study investigated the quantity and the quality of recycled nutrients in three pond-dwelling tadpoles in Japan and how these patterns change with increased resource competition in two species. [ABSTRACT FROM AUTHOR]

Nickel, a micronutrient essential for plant growth and development, has been recognized as a metallic pollutant in wastewater. The concentration of nickel ions in the water course, exceeding the maximum tolerable limit, has called for an alarming attention, due to the bioaccumulative entry in the water–plant–human food chain, leaving a burden of deteriorative effects on visible characteristics, physiological processes, and oxidative stress response in plants. In this work, the renewable utilization of nickel electroplating industrial wastewater effluent (0, 5, 10, 25, 50, and 100%) as a viable source of irrigation water was evaluated using a hydroponic cultivation system, by adopting Lablab purpureus and Brassica chinensis as the plant models, in relation to the physical growth, physiological and morphological characteristics, photosynthetic pigments, proline, and oxidative responses. The elongation of roots and shoots in L. purpureus and B. chinensis was significantly inhibited beyond 25 and 5% of industrial wastewater. The chlorophyll- a , chlorophyll- b , total chlorophyll, and carotenoid contents, accompanied by alterations in the morphologies of xylem, phloem, and distortion of stomata, were recorded in the industrial wastewater-irrigated groups, with pronounced toxicity effects detected in B. chinensis. Excessive proline accumulation was recorded in the treated plant models. Ascorbate peroxidase (APX), guaiacol peroxidase (POD), and catalase (CAT) scavenging activities were drastically altered, with a profound upregulation effect in the POD activity in L. purpureus and both POD and APX in B. chinensis , predicting the nickel-induced oxidative stress. Conclusively, the diluted industrial wastewater effluent up to the optimum concentrations of 5 and 25%, respectively, could be feasibly reused as a renewable resource for B. chinensis and L. purpureus irrigation, verified by the minimal or negligible phytotoxic implications in the plant models. The current findings have shed light on the interruption of nickel-contaminated industrial wastewater effluent irrigation practice on the physical and biochemical features of food crops and highlighted the possibility of nutrient recycling via wastewater reuse in a sustainable soilless cultivation. [ABSTRACT FROM AUTHOR]

Creating an ecologically sustainable circulation of nutrients requires local solutions with commitment from all participating parties. Due to vast differences between various regions, it is very complicated, if not impossible, to create fair, simple, and applicable legislation that can consider all of these differences in a meaningful way. Thus, there is a need for clear and easy ways of developing sustainable and viable solutions locally, as well as communicating them with local community and all the way up to the supervising governmental representatives. To meet this need, we developed a simulation tool that allows the user to explore the effectiveness and impact of a local biorefinery in waste management. As an iterative model based on state machine agents, it can easily be modified for a multitude of scenarios with changes taking place over time, while considering the viewing points of all involved. In this article, we report the first version of this tool and demonstrate its usefulness in estimating suitable biogas reactor size in a biorefinery. [ABSTRACT FROM AUTHOR]

An overlooked effect of ecosystem eutrophication is the potential to alter disease dynamics in primary producers, inducing disease‐mediated feedbacks that alter net primary productivity and elemental recycling. Models in disease ecology rarely track organisms past death, yet death from infection can alter important ecosystem processes including elemental recycling rates and nutrient supply to living hosts. In contrast, models in ecosystem ecology rarely track disease dynamics, yet elemental nutrient pools (e.g. nitrogen, phosphorus) can regulate important disease processes including pathogen reproduction and transmission. Thus, both disease and ecosystem ecology stand to grow as fields by exploring questions that arise at their intersection. However, we currently lack a framework explicitly linking these disciplines. We developed a stoichiometric model using elemental currencies to track primary producer biomass (carbon) in vegetation and soil pools, and to track prevalence and the basic reproduction number (R0) of a directly transmitted pathogen. This model, parameterised for a deciduous forest, demonstrates that anthropogenic nutrient supply can interact with disease to qualitatively alter both ecosystem and disease dynamics. Using this element‐focused approach, we identify knowledge gaps and generate predictions about the impact of anthropogenic nutrient supply rates on infectious disease and feedbacks to ecosystem carbon and nutrient cycling. [ABSTRACT FROM AUTHOR]

Biofloc technology (BFT) is an approach in the rearing of fish and shrimp as a means to support intensive culture, maintain optimum water quality, recycle the nutrients and reduce feed costs. The technology is primarily based on the principle of recycling nitrogenous wastes into microbial biomass that can be assimilated by the cultured animals as feeds or facilitates in maintaining good water quality. The rearing of larvae and juveniles of ornamental fish is confronted with issues on low survival rate, poor water quality and high incidence of diseases. These problems can be mitigated through the use of biofloc technology. From a number of studies reviewed, BFT offers a viable approach in ensuring sustainable production of ornamental fish. The benefits of using this technology include enhancement of water quality by reducing the levels of nitrogenous wastes, efficient feed conversion resulting in better growth and reduction in production costs and better immune response that will enable the fish to have higher resistance against infectious diseases. [ABSTRACT FROM AUTHOR]

Purpose Reuse of landfill leachate is an effective alternative for their nutrients to mitigate decrease in freshwater. On the other hand, the growth of vegetation in the final disposal areas provides many benefits such as improving the visual impact, controlling of hydric erosion, etc. The purpose of this work was to evaluate landfill leachate as irrigation water and source of nutrients for growth of Tagetes erecta L., an ornamental plant with phytoremediation capacities. Method Vegetal growth, physiological responses and mineral elements uptake of the ornamental plant Tagetes erecta L. were studied with different levels of landfill leachate irrigation. The landfill leachate was provided by the municipal waste treatment. Experimental period covered 34 days of daily watering between the beginning and end of the flowering stage. Three different irrigation treatments were used: T1: 10% leachate; T2: 25% leachate; T3: 50% leachate. Hoagland's solution served as the control treatment. Results The irrigation treatment with a dose of 50% leachate causes a clear deterioration in the plant and its flowers. In lower doses, the plant responds favorably to both the production of flowers and the main features of them. Also, the water-use efficiency (WUE) is diminished in those plants irrigated with the major dose of leachate. Conclusion Maintaining controlled doses, landfill leachates can be used as an alternative source of water and nutrients. Irrigation with leachates of these characteristics should be done in dosages not higher than 25% to avoid possible damage of Tagetes erecta L. growth. [ABSTRACT FROM AUTHOR]

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Urban agriculture systems can significantly contribute towards mitigating the impacts of inefficient and complex food supply chains and increase urban food sovereignty. Moreover, improving these urban agriculture systems in terms of nutrient management can lead to a better environmental performance. Based on a rooftop greenhouse in the Barcelona region, we propose a cascade system where the leachates of a tomato cycle from January to July (donor crop) are used as the main irrigation source for five successive lettuce cycles (receiving crop). By determining the agronomic performance and the nutrient metabolism of the system, we aimed to define the potential of these systems to avoid nutrient depletion and mitigate eutrophication, while scaling the system in terms of nutrient supply between the donor and the receiving crops. The results showed that low yields (below 130 g per lettuce plant) are obtained if a cascade system is used during the early stage of the donor crop, as the amount of nutrients in donor’s leachates, specially N (62.4 mg irrigated per plant in the first cycle), was not enough to feed the lettuce receiving crop. This effect was also observed in the nutrient content of the lettuce, which increased with every test until equaling the control (4.4% of N content) as the leachates got richer, although too high electrical conductivity values (near 3 dS/m) were reached at the end of the donor crop cycle. Findings on the uptake of the residual nutrient flows showed how the cascade system was able to take advantage of the nutrients to produce local lettuce while mitigating the effect of N and P in the freshwater and marine environments. Considering our case study, we finally quantified the scale between the donor and receiving crops and proposed three major ideas to optimize the nutrient flows while maintaining the yield and quality of the vegetables produced in the receiving crop.

This study analysed Swedish stakeholders' views on future developments of organic production and consumption based on Organic 3.0, a strategic initiative by the International Federation of Organic Agriculture Movements (IFOAM). Focus group discussions were carried out with actors representing different parts of the organic value chain in Sweden. These identified a number of tensions, four of which represented an unresolved dichotomy in the way forward for the organic movement and its relevance for organic production in most settings. The first tension was between the drive for increased efficiency to achieve higher yields and an agroecological approach with broader sustainability values. The second concerned availability of plant nutrients in organic agriculture including safe recirculating of nutrients from society. The third tension set new technology against the precautionary principle and the notion of naturalness. The fourth concerned the role of organic as an innovation system; whether organic should be a forerunner, i.e. performing well above average and fostering innovation, or whether organic should be a broader movement including more farmers but then requiring more regulations that may hinder innovation. These tensions will result in important choices on direction for the organic sector as it pursues the Organic 3.0 goal of sustainably feeding a growing population based on farming systems based on organic principles. [ABSTRACT FROM AUTHOR]

Purpose: Microalgae present promising green economy applications in the energy and biorefinery sectors. The work concerns a pilot study on the integration of anaerobic digestion with microalgae cultivation for managing at the same time emissions and digestate from the dry anaerobic treatment of organic waste. Methods: Biogas produced was used to feed Solid Oxide Fuel Cell after a filtering step for removing toxic compounds. The exhausts and digestate were used for providing carbon and nutrients for microalgae growth. The experimental workflow includes the characterization of both for defining their suitability in the microalgal growth (Chlorella vulgaris) tests. Results: The exhausts of Solid Oxide Fuel Cells showed relatively stable concentration of CH4 (4–7%) and CO2 (93–96%) and low concentrations (sub ppm(v)) of sulphur, carbonyl and carboxyl, and aromatic compounds and terpenes, making it particularly suited for algae growing as compared with internal combustion engines. The challenging growing conditions are a compromise between carbon recovery and use of digestate. A good microalgae growth has been obtained (22.31 mm3 mL−1 of biovolume corresponding to 151 dry mg L−1 day−1) exploiting ammonia and phosphate from dilute digestate (removal efficiency 94% and 30% respectively) as well as a good carbon recovering (310 mg CO2 L−1 day−1). Conclusions: Based on our data, the integration of microalgae growth and anaerobic digestion process seems a viable solution to achieve (i) reduced emissions due to carbon recovery; (ii) optimum integrated management of anaerobic digestion waste and (iii) biomass production by low-cost nutrients and carbon. [ABSTRACT FROM AUTHOR]

The major issues related to indiscriminate land use are overall related to topsoil depletion, groundwater contamination, plant disease outbreaks, air pollution and greenhouse gas emissions. Currently, global vision focused on the environmental impact and use of eco-friendly strategies are increasing. The design of new agroecosystems and food systems are fundamental to make more sustainability in soil management systems by improving the release of advanced ecosystems services for farmers. Sustainable agriculture utilizes natural renewable resources in the best way due to their intrinsic features by minimizing harmful impact on the agroecosystems. Farmers should sustain or even increase the soil organic matter (SOM) content overall in depleted, semiarid and arid soils. Nutrients recycled from agro-waste into the soil using residual biomass sources should be endorsed by diversified agriculture and governmental policies in which livestock and crop production are spatially integrated. Many good agricultural practices that growers may use to promote soil quality and soil health by minimizing water use and soil pollution on farms are yet available from past years. Exploration of the natural soil biodiversity and manipulation of soil microbiota by continuous amendment with compost, biochar and digestate represents a pre-requisite to develop more efficient microbial consortia useful for soils and crops. On the other hand, more attention is proven regarding the sustainable use of useful microorganisms employed as pure inoculants in rhizosphere. Among them, plant growth-promoting rhizobacteria and biological control agents cover the major groups of tailored inoculants in order to rationalize the internal recycling of nutrients and their energy recovery, or to improve the soil quality and plant health thanks to their diversified mechanisms of action and complex interactions between SOM, microbiota and plant roots in the rhizosphere. [ABSTRACT FROM AUTHOR]

Urban agriculture systems can significantly contribute towards mitigating the impacts of inefficient and complex food supply chains and increase urban food sovereignty. Moreover, improving these urban agriculture systems in terms of nutrient management can lead to a better environmental performance. Based on a rooftop greenhouse in the Barcelona region, we propose a cascade system where the leachates of a tomato cycle from January to July (donor crop) are used as the main irrigation source for five successive lettuce cycles (receiving crop). By determining the agronomic performance and the nutrient metabolism of the system, we aimed to define the potential of these systems to avoid nutrient depletion and mitigate eutrophication, while scaling the system in terms of nutrient supply between the donor and the receiving crops. The results showed that low yields (below 130 g per lettuce plant) are obtained if a cascade system is used during the early stage of the donor crop, as the amount of nutrients in donor's leachates, specially N (62.4 mg irrigated per plant in the first cycle), was not enough to feed the lettuce receiving crop. This effect was also observed in the nutrient content of the lettuce, which increased with every test until equaling the control (4.4% of N content) as the leachates got richer, although too high electrical conductivity values (near 3 dS/m) were reached at the end of the donor crop cycle. Findings on the uptake of the residual nutrient flows showed how the cascade system was able to take advantage of the nutrients to produce local lettuce while mitigating the effect of N and P in the freshwater and marine environments. Considering our case study, we finally quantified the scale between the donor and receiving crops and proposed three major ideas to optimize the nutrient flows while maintaining the yield and quality of the vegetables produced in the receiving crop. [ABSTRACT FROM AUTHOR]

A completely randomized factorial experiment was conducted to evaluate the growth and biomass production of single- and mixed crop species inoculated with mycorrhizae. Radish, (R), safflower (SF), pearl-millet (PM), mustard (M), field peas ((FP), faba-bean (FB), common vetch (CV), and berseem clover (BC) and their blends as R-SF-PM-M, FP-FB-CV-BC, R-SF-PM-M-FP-FB-CV-BC, R-SF-M-FP-FB-CV-BC, and PM-FP-FB-CV-BC were planted in a pot culture. The mycorrhizal inoculum significantly influenced the cover crops growth and biomass production under sterilized soils than that of non-sterile soils. While the safflower produced the highest total biomass, the pearl millet and field peas produced the lowest total biomass. Generally, in sterile and mycorrhizal conditions plant grown better and have high total C fixation. Within non-sterile and mycorrhizal inoculation, Safflower (1383.1 g C m−2) and Berseem Clover (1235.5 g C m−2) as a single species have fixed highest amount of carbon as biomass. Mycorrhizae inoculated BC+CV+FB+FP+SF+PM blends had a return of 1365.0 g C m−2 in non-sterile soil. Our results suggested that cover crops in single or mixed stands with mycorrhizal inoculations are expected to provide a significantly greater amount of biomass, which would contribute to soil organic matter and nutrient recycling for crop production. [ABSTRACT FROM AUTHOR]

This study was based on data obtained during the cruise 63 of the R/V Akademik Mstislav Keldysh in September 2015. We examine the features of the hydrochemical structure of the Lena River–Laptev Sea mixing zone. The studies were carried out in the eastern part of the Laptev Sea on a quasi-meridional transect, with the length of 710 km along 130°30' E. The distribution of dissolved oxygen, pH, alkalinity, major nutrients (phosphates, silicon, nitrate, and ammonium nitrogen), and chlorophyll a was analyzed. The relationship between the main hydrochemical parameters and chlorophyll a was considered. The distribution of hydrochemical parameters is similar to the data of previous studies: significant removal of silicon by waters of the Lena River (66.6 μM) with a moderate nitrate content (3.87 μM) and low concentration of mineral phosphorus (0.08 μM) in the area of strong influence of river runoff (salinity of 3.012 PSU). The presence of a near-bottom stagnant water zone in the part of research area affected by river runoff was detected. It is shown that the influx of mineral forms of nitrogen and phosphorus into the marine region of the Lena River delta occurs mostly as a result of nutrient recycling rather than due to the continental runoff. [ABSTRACT FROM AUTHOR]

Promotion of the circular economy (CE) has become one of the key policy objectives in the EU in the late 2010s. The power of the concept lies in the promise of decoupling economic growth from the increasing usage of virgin resources by closing the material loops. In this article, we investigate the material politics of the CE by means of an in-depth case study of how one pioneering biogas company in Finland struggled to undo a disruptive regional manure surplus by turning it into a resource in energy and fertilizer production. We treat this novel nutrient recycling business model as a political technology that aimed to rearrange existing metabolic relations in order to solve the problem of intensive pig farming that generated too much manure for sustainable utilization in the area. At the same time, their business model clashed with the various categorizations and technologies of governance that stabilized the status quo. These clashes embody the underlying societal tensions of the CE transition, which do not manifest themselves as open conflicts in public arenas. We claim that these obstacles point to challenges of unmaking material surplus with CE business models when the surrounding economy leans on a linear material flows and keeps growth on track. [ABSTRACT FROM AUTHOR]

In this paper, a planktonic resource–consumer system with two delays is investigated and the coefficients depend on τ one of the two delays. Firstly, the property of solution and the existence of equilibrium are given. The dynamical analysis of the system including stability and Hopf bifurcation by using the delays as parameters is carried out. Both the single delay and two delays can cause the system to produce Hopf bifurcation and the stable switching phenomena may exist. Furthermore, using the crossing curve methods, we obtain the stable changes of equilibrium in two-delay parameter plane, which generalizes the results of the system that the coefficients do not depend on delay. Furthermore, the numerical simulation results show that the theoretical analyses are correct when the delays change. [ABSTRACT FROM AUTHOR]