This study evaluates the economic and environmental benefits of implementing the proposed REcovered Nitrogen from manURE (RENURE) criteria as mineral fertiliser into the Nitrates Directive (ND) to facilitate the utilisation of minerals from manure. Implementing the RENURE amendment could significantly contribute to sustainability goals in an economic way, offering a 4.8 % reduction in economic costs in livestock-dense regions including Brittany (-0.7 %), Lombardy (-2.3 %), Flanders (-2.6 %), Lower Saxony (-4.7 %), Catalonia (-4.8 %), North-Rhine Westphalia (-4.8 %), and the Netherlands (-5.0 %). Through spatially explicit multi-agent modeling, the study revealed that the RENURE amendment not only promises economic benefits, but also enhances nitrogen circularity by 1.3 % and reduces greenhouse gas emissions by 6 % in these areas. These findings highlight the potential of nutrient recovery and reuse under RENURE to address both economic and environmental challenges, supporting the European Union's (EU) Farm-to-Fork strategy (F2F) goals of reducing nutrient emissions to the air and fertilizer use.

Critical source areas (CSAs) are small areas of a field, farm, or catchment that account for most contaminant loss by having both a high contaminant availability and transport potential. Most work on CSAs has focused on phosphorus (P), largely through the work in the 1990s initiated by Dr. Sharpley and colleagues who recognized the value in targeting mitigation efforts. The CSA concept has been readily grasped by scientists, farmers, and policymakers across the globe. However, experiences and success have been mixed, often caused by the variation in where and how CSAs are defined. For instance, analysis of studies from 1990 to 2023 shows that the proportion of the annual contaminant load coming from a CSA decreases from field to farm to catchment scale. This finding is consistent with increased buffering of CSAs and greater contribution of other sources with scale, or variation in the definition of CSAs. We therefore argue that the best application of CSAs to target mitigation actions should be at small areas that truly account for most contaminant loss. This article sheds light on the development and utilization of CSAs, paying tribute to Dr. Sharpley's remarkable contributions to the improvement of water quality, and reflecting upon where the CSA concept has succeeded or not in reducing contaminant (largely P) loss.

Recycling of organic resources into agriculture has the potential to greatly increase nutrient use efficiency and improve soil carbon balance, but improper management can have adverse effects on the environment. Agriculture therefore faces large challenges to increase yields while decreasing these emissions to the environment. In this paper, we review (i) the availability and composition of organic resources, (ii) their agronomic value and risk of emissions, (iii) potential measures to reduce their emissions, and (iv) future challenges to support farmers and policy makers. The total amount of organic resource applied to soil amounted on average 41 kg nitrogen per ha agricultural land, 9 kg phosphorus per ha, and 456 kg carbon per ha in EU-27 + UK in 2017. Solid pig and cattle manures and cattle slurry are the most used organic resources. The availability of new organic resources from food processing, sewage sludge, municipal bio-wastes, and upcoming manure treatment techniques as fertilizer or soil conditioner is expected to strongly increase over the coming decade. Insight is needed into the composition of organic resources, the plant-availability of nutrients, the degradability of organic matter and the presence of contaminants. Measurement techniques become available to characterize soils, manures, crops, and emissions to the environment. However, the interpretation, and integration of data, and recommendations to farmers and policymakers using large amounts of data is expected to become more and more challenging. Many measures are available to improve nutrient and carbon management and to reduce emissions, including proper application, technological measures and structural changes in agriculture. For many measures, there is a risk of trade-offs that could lead to pollution swapping at different scales. We should focus on finding synergies between measures and no-regret management choices to develop effective mitigation strategies. The main future challenge for managing organic resources in agriculture is the development of an integrated nutrient management approach, including (i) the characterization of organic resources, their agronomic value and their environmental risks, (ii) knowledge of potential synergies and trade-offs between management measures, and (iii) implementation of this knowledge into decision support tools, models and legislation to support farmers and policy makers.

Processed manure products have the potential to substitute chemical fertilizers and the use of these products may increase resource efficiency in the food system and decrease emissions of ammonia (NH3) and greenhouse gasses (GHG). The yields of maize and grass, as well as emissions, have been determined from a processed manure product: liquid ammonium sulfate from nitrogen stripping animal manure (AS), in comparison to a regular mineral fertilizer, calcium ammonium nitrate (CAN), in a greenhouse experiment and a field demonstration using a sandy and a clay soil. NH3 emissions were determined by comparing AS with a dairy manure as a reference. The yield of both crops, their nitrogen nutrient use efficiency (NUE), and nitrous oxide (N2O) emissions were not significantly different, while NH3 emission was lower from AS compared to the dairy manure. As a side-effect, the sulfur (S) contents of the grass in the fields fertilized with AS were much higher than in the non-fertilized control. We conclude that AS, produced here with a pH < 5.5, can be used as an alternative for CAN in Dutch dairy systems, or similar other system, if S leaching losses do not pose a problem for the environment. Meanwhile, care should be taken not to exceed S in feed above toxic levels for ruminants.

Highly stabilized digestate from sewage sludge and digestate-derived ammonium sulphate (RFs), were used in a comparison with synthetic mineral fertilizers (SF) to crop maize in a three-year plot trial in open fields. RFs and SF were dosed to ensure the same amount of mineral N (ammonia-N). In doing so, plots fertilized with digestate received much more N (+185 kg ha-1 of organic N) because digestate also contained organic N. The fate of nitrogen was studied by measuring mineral and organic N in soil at different depths, ammonia and N2O emissions, and N uptake in crops. Soil analyses indicated that at one-meter depth there was no significant difference in nitrate content between RF, SF and Unfertilized plots during crop season indicating that more N dosed with digestate did not lead to extra nitrate leaching. Ammonia emissions and N content in plants and grains measured were also similar for both RF and SF. Measuring denitrification activity by using gene makers resulted in a higher denitrification activity for RF than SF. Nevertheless, N2O measurements showed that SF emitted more N2O than RF (although it was not statistically different) (7.59 ± 3.2 kgN ha-1 for RF and 10.3 ± 6.8 kgN ha-1 for SF), suggesting that probably the addition of organic matter with digestate to RF, increased the denitrification efficiency so that N2 production was favoured. Soil analyses, although were not able detecting N differences between SF and Rf after three years of cropping, revealed a statistical increasing of total carbon, suggesting that dosing digestate lead to carbon (and maybe N) accumulation in soil. Data seem to suggest that N2O/N2 emission and organic N accumulation in soil can explain the fate of the extra N dosed (organic-N) in RF plots.

Recovered fertilizers (a highly stabilized digestate and ammonium sulphate) obtained from anaerobic digestion of sewage sludge, were used on plot trials with a maize crop, in a comparison with synthetic fertilizers. After three consecutive cropping seasons, the soils fertilized with the recovered fertilizers (RF), compared to those fertilized with synthetic fertilizers (SF), did not show significant differences either in their chemical characteristics or in the accumulation of inorganic and organic pollutants (POPs). The RF ensured an ammonia N availability in the soil equal to that of the soil fertilized with SF, during the whole period of the experiment. Furthermore, no risks of N leaching were detected, and the use of RF did not result in a greater emission of ammonia or greenhouse gases than the use of SF. The agronomic results obtained using RF were equivalent to those obtained with SF (fertilizer use efficiency of 85.3 ± 10 and 93.6 ± 4.4% for RF and SF respectively). The data show that utilising a very stable digestate can be a good strategy to produce a bio-based fertilizer with similar performance to that of a synthetic fertilizer, without environmental risks.

The research was undertaken as part of

The research was undertaken as part of the project called SYSTEMIC: 'Systemic large scale

Anaerobic digestion of nitrogen (N) rich substrates might be hindered when ammonia (NH3) formation reaches toxic levels for methanogenic microorganisms. One possible strategy to avoid inhibiting conditions is the removal of NH3 from digestate by stripping and scrubbing technology and by recirculating N depleted digestate back to the digester. This study aimed to i) monitor the performance (mass and energy balances) of a full scale digestate processing cascade that includes an innovative vacuum side stream NH3stripping and scrubbing system, ii) assess the production cost of ammonium sulphate (AS) solution and iii) evaluate its fertiliser quality. The use of gypsum to recover NH3 in the scrubbing unit, instead of the more common sulphuric acid, results in the generation of AS and a fertilising liming substrate. Mass and nutrient balances indicated that 57% and 7.5% of ammonium N contained in digestate was recovered in the form of a 22% AS and liming substrate, respectively. The energy balance showed that about 3.8 kWhel and 59 kWhth were necessary to recover 1 kg of N in the form of AS. Furthermore, the production cost of AS, including both capital and operational costs, resulted to be 5.8 euro t-1 of digestate processed. According to the fertiliser quality assessment, this technology allows for the recovery of NH3in the form of salt solutions that can be utilised as a substitute for synthetic mineral nitrogen fertilisers.

Phosphorus (P) is an essential element to all living beings but also a finite resource. P-related problems center around broken P cycles from local to global scales. This paper presents outcomes from the 9th International Phosphorus Workshop (IPW9) held 2019 on how to move towards a sustainable P management. It is based on two sequential discussion rounds with all participants. Important progress was reported regarding the awareness of P as finite mineable resource, technologies to recycle P, and legislation towards a circular P economy. Yet, critical deficits were identified such as how to handle legacy P, how climate change may affect ecosystem P cycling, or working business models to up-scale existing recycling models. Workshop participants argued for more transdisciplinary networks to narrow a perceived science-practice/policy gap. While this gap may be smaller in reality as illustrated with a Swiss example, we formulate recommendations how to bridge this gap more effectively.

Business case evaluation of five centralised anaerobic digesters applying nutrient recovery and reuseA product from the H2020 project SYSTEMIC Hermann, L.

This final report of the four-year PPS (public-private collaboration) project ‘Meerwaarde Mest en Mineralen 2 (More Value from Manure and Minerals 2): nutrient recovery from manure’ contains the evaluation of five large-scale installations for processing of animal manure or co-digested animal manure (digestate). The different processing techniques of the installations include hygienisation, solid-liquid separation, drying and pressing of the solid fraction and production of mineral concentrate and dischargeable water by means of membrane filtration and ion exchangers or by means of membrane filtration and biological treatment. Based on a performed monitoring of the installations the achieved separation efficiencies, (nutrient) mass balances, processing costs and composition, agronomic and environmental quality of the end products, have been evaluated. Also the environmental gains of processing were calculated via a simplified life cycle assessment (LCA). Moreover, the construction, monitoring and evaluation of an innovative installation which separates the solid fraction of co-digested animal manure into a phosphate (P) fertiliser and an organic low-P soil improver was a central part of the project. Finally, recommendations are given for environmentally beneficial adaptations of manure processing installations in the Netherlands.

The use of digestate in agriculture represents an opportunity for reducing the use of synthetic fertilizers while promoting nutrient and organic matter recycling, i.e. contributing to a circular economy. However, some environmental impacts could result from digestate use, with particular reference to N emissions, which can contribute to particulate matter formation in the atmosphere. So, correct digestate spreading methods need to be tested to reduce ammonia emission and, possibly, also to avoid annoyance to the inhabitants. In this work a digestate from organic wastes was used as a fertilizer by its injection at 15 cm, in comparison with a synthetic one ( urea) for three consecutive years in open fields, measuring ammonia and odours emission. On average, the ammonia emission from digestate was of 25.6 +/- 9.4 kg N Ha(-1) (11.6% +/- 4 of Total Ammonia Nitrogen - TAN - dosed), while urea emitted 24.8 +/- 8.3 kg N Ha(-1) (13.4% +/- 4.5 of TAN dosed). The injected digestate also emitted less odour than urea (601 +/- 531 and 1767 +/- 2221 OU m(-2) h(-1), respectively), being ammonia coming from urea hydrolysis responsible for odour productions. The different N fertilizers did not lead to differences in crop yields, i.e. 18.5 +/- 2.9 Mg grain Ha(-1) and 17.4 +/- 1.2 Mg grain Ha(-1) for digestate and urea respectively. (C) 2021 Elsevier B.V. All rights reserved.

Het ministerie van LNV bereidt een subsidieregeling voor om mestverwerking te stimuleren. Gedacht wordt aan een investeringssubsidie voor de verwerking van mest – in eerste instantie gericht op varkensmest – tot verwerkte mestproducten die stikstofkunstmest kunnen vervangen. Het ministerie van LNV heeft Wageningen Research gevraagd om inzicht te geven in de effecten van het vervangen van stikstofkunstmest door kunstmestvervangers uit dierlijke mest op ammoniak- en broeikasgasemissies. In een quickscan op basis van bestaand onderzoek is nagegaan wat de ammoniak- en broeikasgasemissies zijn bij productie en toepassing van de kunstmestvervangers mineralenconcentraten, ammoniumsulfaat en ammoniumnitraat uit mest. Dit zijn producten die mogelijk op termijn als stikstofkunstmestvervangers in het kader van de Nitraatrichtlijn kunnen worden toegepast. Deze producten worden door de Europese Commissie aangeduid met de term RENURE (REcovered Nitrogen from manURE). NEMA (National Emission Model Agriculture) is het model dat gebruikt wordt voor de berekening van de emissies van ammoniak en broeikasgassen uit de landbouw op landelijk niveau voor de Nationale Emissie Registratie. Als LNV mestbewerking tot kunstmestvervanger als maatregel wil inzetten in het stikstof- en klimaatdossier, dan moeten de emissies die optreden bij productie en toepassing van kunstmestvervangers opgenomen worden in het NEMA-model. Berekeningen met NEMA voor een scenario waarbij 25% van de varkensmest in Nederland wordt verwerkt tot mineralenconcentraat laten beperkte effecten zien op emissies: de ammoniakemissie neemt iets toe (0,5 kton NH3), de lachgasemissie neemt iets af (-0,1 kton N2O) en de methaanemissie verandert niet. De onzekerheden in deze berekeningen met NEMA zijn echter groot, omdat er weinig gegevens beschikbaar zijn over emissies bij productie en toepassing van kunstmestvervangers waarmee NEMA geparametriseerd kan worden. Het vervangen van kunstmest door kunstmestvervangers kan leiden tot minder energiegebruik indien het energieverbruik van de productie en toepassing van de kunstmestvervanger lager is dan die van de productie van kunstmest. Het is bekend dat ook mestbewerking veel energie kan vragen, zoals de omgekeerde osmosetechniek bij de productie van mineralenconcentraten en het strippen van ammonium uit mest. Belangrijke factoren hierbij zijn het al dan niet vergisten van de mest, de transportafstand en de landbouwkundige werking van de kunstmestvervanger. Verschillende projecten zullen later in 2021 een beter beeld geven over het energiegebruik bij productie en toepassing van kunstmestvervangers. Afleiden van de voordelen in termen van energieverbruik vraagt om een LCA- studie, waarbij alle processtappen beschouwd worden en vergeleken worden met een referentiescenario. Als de dikke fractie die wordt geproduceerd tijdens productie van kunstmestvervangers aan Nederlandse landbouwgronden wordt toegediend, kan de toegevoegde koolstof bijdragen aan de vermindering van CO2-emissies door koolstofopslag. Echter, de dosering van organische stof wordt hierbij beperkt door het hoge fosfaatgehalte van dikke fracties uit mest. Er wordt geëxperimenteerd met technieken om fosfaat uit mest te halen, zodat er een fosfaatarme dikke fractie overblijft, waarmee binnen de fosfaatgebruiksnormen meer organische stof aan landbouwgronden kan worden toegediend. Deze quickscan geeft een eerste indruk van de effecten van toepassing van kunstmestvervangers geproduceerd uit mest op ammoniak- en broeikasgasemissies. Als er aanvullende maatregelen worden genomen (zoals een korte opslagduur en emissiearme opslag van de mest en mestproducten en verbeterde emissiearme toediening van producten uit mestbewerking), dan zijn er perspectieven om ammoniak- en broeikasgasemissies te beperken door vervanging van kunstmest door kunstmestvervangers. Er zijn echter veel onzekerheden en de rekenmethoden van emissies die voor het Nederlandse beleid worden toegepast, zoals NEMA, moeten worden verbeterd. Hiervoor is experimenteel onderzoek nodig. Ook is meer onderzoek nodig naar het energieverbruik tijdens mestbewerking.In 2021 en daarna zijn er nog diverse lopende projecten naar de ammoniak- en broeikasgasemissies en het energieverbruik bij productie en toepassing van kunstmestvervangers alsmede de landbouwkundige werking van deze meststoffen. Er is echter geen overzicht of dit onderzoek alle vragen beantwoordt en bruikbare gegevens oplevert voor inpassing van kunstmestvervangers in het NEMA-model. Geadviseerd wordt om in beeld te brengen welk onderzoek er loopt en of er extra onderzoek nodig is op onderdelen die nu niet worden onderzocht teneinde het NEMA-model te kunnen parametriseren.

This work reports a full-scale study in which organic wastes were transformed by high-solid thermophilic anaerobic digestion (HSAD), into N fertilizers and organic fertilizers, i.e. digestate. The produced fertilizers were characterized over 42 months and their properties were discussed in comparisons with literature data. HSAD coupled with N stripping technology led to ammonia sulphate production having high N concentration (74 +/- 2 g kg-1 wet weight), neutral pH (6.8 +/- 1.3) and low traces of other elements. Digestate showed both higher carbon (C) content (314 +/- 30 g kg-1 on dry matter (DM) and biological stability than green composts, indicating good amendment properties. Digestate was also interesting for its N (77 +/- 3.7 g kg-1 dry matter-DM) content, half of it in the ammonia form, and P content (28 +/- 4.1 g kg-1 DM) that was 43% readily available as soluble P-orthophosphate. K content was low (6.5 +/- 1.3 g kg-1 DM), indicating poor fertilizing ability of digestate for this element. All organic pollutants investigated were much lower than the limits required for agricultural use and levels of some of them were lower than the content revealed for other organic matrices such as agricultural and energy crop digestates and compost. Emerging pollutants (i.e., pharmaceuticals) were tested as markers and they were found to be below the detection limit (<0.01 mg kg-1 DM) indicating very low content. The results obtained showed that HSAD coupled with N stripping allowed transforming sewage sludge into fertilizers and soil improvers exploitable in agriculture. (c) 2021 Elsevier Ltd. All rights reserved.

Purpose This study investigated the C and N mineralisation potential of solid fractions (SFs) from co-digestated pig manure after P-stripping (P-POOR SF) in comparison with P-rich SFs, as a means to estimate their organic matter stability in soil. Compost (COMP) and biochar (BCHR) (made from P-POOR SF) were also included in the study as reference biosolids. Methods The SFs were incubated in a sandy-loam soil under moist conditions to determine production of CO 2 and mineral N. At specified intervals, CO 2 evolution in the mixtures was measured via the alkali trap method and titration over a period of 81 days, while mineral N was measured using a flow analyser after KCl extraction over a period of 112 days. Results The various SFs showed similar patterns of C mineralisation (15–26% of added total C in 81 days) that were clearly higher than for COMP and BCHR (6% and 7%, respectively). Temporary N immobilisation was observed in biosolids with a high C/N ratio. The effective organic matter (EOM) of the SFs was calculated based on the C mineralisation data and varied between 130 and 369 kg Mg −1 . Conclusions The SF with a reduced P content had a high EOM/P ratio which is beneficial in areas where P status of the soil is already high. Moreover, the N mineralisation patterns confirm that a high C/N ratio may also reduce risks for N leaching due to temporary N immobilisation.