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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]

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]

[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 priming effect (PE) in soil, when induced by a fresh carbon supply, is believed to result from two different mechanisms, “stoichiometric decomposition” and “nutrient mining”, and contributes to either long-term SOM stabilization or depletion. Understanding how to affect the balance between both mechanisms can provide valuable insight into agroecology, especially in Southern countries where organic matter management is the primary method of fertilizing cultivated plots. Therefore, the objective of this study was to investigate the bacterial actors in each mechanism and the influence of three drivers in Malagasy Ferralitic soils: the quality of the inducing substrate, the quality of the SOM, and the soil nutrient status. Three different agricultural Ferralitic soils, characterized by different levels of NH 4 and PO 4 availability, different SOM size fractionation profiles, and different bacterial communities, were amended with three types of 13 C-labeled organic substrate (glucose, wheat residue, and rice residue) and the PE was measured at two incubation times (7 and 42 days). The results showed that a PE generated by stoichiometric decomposition was mainly induced by the polymerized fraction of crop residues, especially in soil enriched by decaying plant tissues, mineral N, and its associated decomposers guild such as Verrucomicrobia, α- and δ-Proteobacteria and Actinomycetes. Conversely, when this young SOM pool was reduced, the PE was mainly generated by N mining, especially when induced by soluble compounds and when N was limiting but P was available. [ABSTRACT FROM AUTHOR]

Increased nutrient cycling in the agri-food system is a way to achieve a healthier nutrient stewardship and more sustainable food production. In life cycle assessment (LCA) studies, use of recycled fertilizer products is often credited by the substitution method, which subtracts the environmental burdens associated with avoided production of mineral fertilizer from the system under study. The environmental benefits from avoided fertilizer production can make an important contribution to the results, but different calculation principles and often implicit assumptions are used to estimate the amount of avoided mineral fertilizer. This may hinder comparisons between studies. The present study therefore examines how the choice of substitution principles influences LCA results. Three different substitution principles, called one-to-one, maintenance, and adjusted maintenance, are identified, and we test the importance of these in a case study on cattle slurry management. We show that the inventory of avoided mineral fertilizer varies greatly when the different principles are applied, with strong influences on two-thirds of LCA impact categories. With the one-to-one principle, there is a risk of systematically over-estimating the environmental benefits from nutrient cycling. In a sensitivity analysis we show that the difference between the principles is closely related to the application rate and levels of residual nutrients in the soil. We recommend that LCA practitioners first and foremost state and justify the substitution method they use, in order to increase transparency and comparability with other studies. [ABSTRACT FROM AUTHOR]

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

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]

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

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

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

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

We discuss several gradostat models in which a microbial population excretes a dissolved toxin, which in some cases can get recycled back into the system as a nutrient source. Each mathematical model consists of six ordinary differential equations and represents the dynamics of harmful algal blooms in a two compartment gradostat, for example representing lakes with fringing coves. We examine three different modes of toxin production, related to the algal growth rate, mortality rate, and nutrient limitation, respectively. Local and global stability analysis of the equilibria predict that algal abundance and toxin concentration can be both washed out or both persist under different environmental conditions. All theoretical results are supported by a set of numerical simulations. [ABSTRACT FROM AUTHOR]

Harmful algal blooms that disrupt and degrade ecosystems (ecosystem disruptive algal blooms, EDABs) are occurring with greater frequency and severity with eutrophication and other adverse anthropogenic alterations of coastal systems. EDAB events have been hypothesized to be caused by positive feedback interactions involving differential growth of competing algal species, low grazing mortality rates on EDAB species, and resulting decreases in nutrient inputs from grazer-mediated nutrient cycling as the EDAB event progresses. Here we develop a stoichiometric nutrient–phytoplankton–zooplankton (NPZ) model to test a conceptual positive feedback mechanism linked to increased cell toxicity and resultant decreases in grazing mortality rates in EDAB species under nutrient limitation of growth rate. As our model EDAB alga, we chose the slow-growing, toxic dinoflagellate Karenia brevis , whose toxin levels have been shown to increase with nutrient (nitrogen) limitation of specific growth rate. This species was competed with two high-nutrient adapted, faster-growing diatoms ( Thalassiosira pseudonana and Thalassiosira weissflogii ) using recently published data for relationships among nutrient (ammonium) concentration, carbon normalized ammonium uptake rates, cellular nitrogen:carbon (N:C) ratios, and specific growth rate. The model results support the proposed positive feedback mechanism for EDAB formation and toxicity. In all cases the toxic bloom was preceded by one or more pre-blooms of fast-growing diatoms, which drew dissolved nutrients to low growth rate-limiting levels, and stimulated the population growth of zooplankton grazers. Low specific grazing rates on the toxic, nutrient-limited EDAB species then promoted the population growth of this species, which further decreased grazing rates, grazing-linked nutrient recycling, nutrient concentrations, and algal specific growth rates. The nutrient limitation of growth rate further increased toxin concentrations in the EDAB algae, which further decreased grazing-linked nutrient recycling rates and nutrient concentrations, and caused an even greater nutrient limitation of growth rate and even higher toxin levels in the EDAB algae. This chain of interactions represented a positive feedback that resulted in the formation of a high-biomass toxic bloom, with low, nutrient-limited specific growth rates and associated high cellular C:N and toxin:C ratios. Together the elevated C:N and toxin:C ratios in the EDAB algae resulted in very high bloom toxicity. The positive feedbacks and resulting bloom formation and toxicity were increased by long water residence times, which increased the relative importance of grazing-linked nutrient recycling to the overall supply of limiting nutrient (N). [ABSTRACT FROM AUTHOR]

Highlights: [•] Direct field emissions from organic fertilizer dominated environmental impacts. [•] The amount of avoided mineral fertilizers largely influenced environmental impacts. [•] Modified plant available nitrogen calculation considers total nitrogen emissions. [•] Calculation method for amount of avoided mineral fertilizers. [ABSTRACT FROM AUTHOR]

Abstract: We evaluate the relative importance of the causal connection between exogenous total phosphorus (TP) loading and internal nutrient recycling with the water quality conditions in the Bay of Quinte, Ontario, Canada. First, we examine the temporal trends of all the major point and non-point loading sources over the last four decades. We then enhance the mechanistic foundation of an existing simple mass-balance total phosphorus (TP) model, originally developed to guide the eutrophication management in the system. The structural improvements include the incorporation of macrophyte dynamics, the explicit representation of the role of dreissenids in the system, and the improved portrayal of the interplay between water column and sediments. The upgraded model was in good agreement with the observed TP variability in the system during the study period (2002–2009) and successfully reproduced the TP accumulation patterns toward the end of the summer-early fall. We provide evidence that phosphorus dynamics in the upper Bay are predominantly driven by the inflows from Trent River, while the middle and lower segments likely receive substantial internal subsidies from the sediment diagenesis mechanisms and/or the activity of macrophytes and dreissenids (e.g., pseudofeces production, nutrient pump effect). We also forced the model with scenarios of reduced nutrient loading and examine the likelihood of the system to meet its water quality delisting targets, although we caution that our complex overparameterized modeling construct is primarily intended for heuristic purposes. The present study together with the companion paper by Zhang et al. (2013) illustrate how phosphorus mass balance models can offer useful tools for improving our understanding of freshwater ecosystems. [Copyright &y& Elsevier]

Abstract: A model of competition between plasmid-bearing and plasmid-free organisms in the chemostat with periodic input of nutrient and two distributed delays is investigated. The delays model the fact that the nutrient is partially recycled after the death of the biomass by bacterial decomposition. It is assumed that there is inter-specific competition between the plasmid-bearing and plasmid-free organisms as well as intra-specific competition within each population. Analysis of the extinction of the organisms, including plasmid-bearing and plasmid-free organisms, and the permanence of the system are carried out. Furthermore, sufficient conditions ensuring the existence and global stability of the positive periodic solution are established. Numerical simulations illustrate the theoretical results. Finally, we present a procedure by which one can control the parameters of the model to keep the plasmid-bearing organism stay eventually in a desired set. [Copyright &y& Elsevier]

Abstract: In an effort to generate more information on the use of biosolids in the turf industry, a study was conducted to compare the effectiveness of biosolids with recommended organic sources in enhancing soil microbial populations and N availability in putting green sand rootzones. The treatments included four types of rootzones as follows: sand (control), sand mixed with Dakota reed-sedge peat (10%, v/v), sand mixed with yard-waste compost (10%, v/v), and sand mixed with biosolids (10%, v/v), which were established at the North Shore Country Club golf course, Glenview, IL, USA in 1997. All plots received the same fertilizers mainly in organic forms at 100kgNha−1 year−1. Creeping bentgrass (Agrostis palustris) turf was established, and was managed as a practice putting green. Soil microbial biomass in the rootzone (0–30cm) was higher either under compost (fall 2004 and summer 2005) or biosolids (summer 2003) than other treatments. Rootzone ammonium oxidizer populations were higher with biosolids (5400g−1 soil) than peat (1200g−1 soil) and compost (500g−1 soil) amendment and in control (400g−1 soil) in summer 2003. The nitrite oxidizer populations were higher with biosolids (24000g−1 soil) than compost (8300g−1 soil) and peat (4700g−1 soil) amendment and in control (3700g−1 soil) in summer 2005. Soil potentially mineralizable N, also being lowest in control, was higher in the biosolids-amended than compost- and peat-amended rootzones. In most seasons, the nitrate concentrations in biosolids rootzone (3.16–19.3mgkg−1) were higher than in compost (2.79–17.7mgkg−1), peat (1.83–14.4mgkg−1), and control rootzone (0.81–15.2mgkg−1). The study indicates that while compost could restore soil microbial biomass better than peat, biosolids could maintain greater N supply than peat and compost. [Copyright &y& Elsevier]

The concept of a food web has been a central organising theme in ecology ever since its classical development. Studies of nutrient–autotroph–herbivore system require special attention in this context. In this paper, we have proposed and analysed a nutrient–autotroph–herbivore system with instantaneous nutrient recycling. We have observed that if the external nutrient input exceeds certain threshold determined by the other parameters of the system, then the system is locally as well as globally asymptotically stable around the positive interior equilibrium. Moreover, to observe the effect of environmental stochasticity on such system, the deterministic model has been modified by allowing random fluctuations around the positive interior equilibrium. The stochastic stability properties of the model have been investigated both analytically and numerically suggesting that the deterministic model is robust with respect to stochastic perturbations. Suitable thresholds of the intensity of the stochasticity have been obtained to control the system under the influence of environmental stress. [Copyright &y& Elsevier]

To facilitate understanding and decision making in the food-energy-water (FEW) nexus context, we develop an integrated technology-environment-economics model (ITEEM) at a watershed scale. ITEEM is built as an integration of various models, including models for grain processing, drinking water treatment, and wastewater treatment (technology); a watershed model for hydrology, water quality, crop production, and nutrient cycling (environment); an economics model assessing total benefit, including non-market valuation of environmental benefits. Different data techniques are applied to develop suitable surrogates for computer-based models, including a response matrix method, artificial neural networks, and lookup tables. Empirical equations are applied to develop models of economics and drinking water treatment. The input-output relationships between the models are formulated in a unified computational framework. ITEEM, a spatially semi-distributed dynamic simulation model, can be used to quantify the environmental and socioeconomic impacts of various management practices, technologies, and policy interventions on FEW systems in the Corn Belt. • Selected data techniques are applied to develop suitable surrogates for different process models. • The integrated Technology-Environment-Economics model based on surrogates is computationally tractable. • Insights on surrogate-based model coupling and tradeoffs of integration design choice are discussed. • The integrated model is demonstrated for FEW systems in the Corn Belt. • The sensitivity of 16 key parameters from component models on the integrated model is evaluated. [ABSTRACT FROM AUTHOR]

Buildings in cities represent potential point sources of human excreta-derived nutrients, while agricultural land in (peri)urban areas demand nutrients as fertilizers. Here we present a new geographic information system (GIS)-based modelling tool, Resource Dynamo, that optimizes the allocation of excreta-derived nutrients from buildings in cities to nearby agricultural fields. The model minimizes the number of supply sites needed to match the demand by prioritizing sites with the highest nutrient supply, i.e. the hotspots. Furthermore the model delineates exact transport routes between the discrete supply and demand sites. The transport distances are minimized as transport costs are a key factor for economic viability of nutrient management. The high resolution of the model allows it to function as a decision-support tool for bringing cyclic nutrient management into practice. To disclose the potential of the model, we used it to match phosphorus supply in human-derived urine with phosphorus demands from agricultural fields within the municipality of Amsterdam on a temporal scale of 1 year. • Geospatial transport distance optimization between nutrient supply and demand sites. • In Amsterdam, 38% of phosphorus supply from human urine covers agricultural demand. • Average transport distances between supply and demand sites were under 11 km. • Visualization with Resource Dynamo can support decision-making towards nutrient cycling. [ABSTRACT FROM AUTHOR]

Recovering resources from wastewater systems is increasingly being emphasised. Many technologies exist or are under development for recycling nutrients such as nitrogen and phosphorus from wastewater to agriculture. Planning and design methodologies are needed to identify and deploy the most sustainable solutions in given contexts. For the environmental sustainability dimension, life cycle assessment (LCA) can be used to assess environmental impact potentials of wastewater-based nutrient recycling alternatives, especially nitrogen and phosphorus recycling. This review aims to evaluate how well the LCA methodology has been adapted and applied for assessing opportunities of wastewater-based nutrient recycling in the form of monomineral, multimineral, nutrient solution and organic solid. We reviewed 65 LCA studies that considered nutrient recycling from wastewater for agricultural land application. We synthesised some of their insights and methodological practices, and discussed the future outlook of using LCA for wastewater-based nutrient recycling. In general, more studies suggested positive environmental outcomes from wastewater-based nutrient recycling, especially when chemical inputs are minimised, and source separation of human excreta is achieved. The review shows the need to improve methodological consistency (e.g., multifunctionality, fertiliser offset accounting, contaminant accounting), ensure transparency of inventory and methods, consider uncertainty in comparative LCA context, integrate up-to-date cross-disciplinary knowledge (e.g., agriculture science, soil science) into LCA models, and consider the localised impacts of recycled nutrient products. Many opportunities exist for applying LCA at various scales to support decisions on wastewater-based nutrient recycling – for instance, performing "product perspective" LCA on recycled nutrient products, integrating "process perspective" LCA with other systems approaches for selecting and optimising individual recovery processes, assessing emerging nutrient recovery technologies and integrated resource recovery systems, and conducting systems analysis at city, national and global level. Image 1 • We reviewed 65 LCA studies related to nutrient recycling (N, P) from wastewater. • More studies suggested positive environmental outcomes from nutrient recycling. • More methodological consistency, transparency and uncertainty analysis are needed. • Contaminants accounting and product application modelling are to be improved. • Many opportunities exist for applying LCA at various scales for nutrient recycling. [ABSTRACT FROM AUTHOR]