To mitigate the risk of eutrophication and minimize adverse environmental impacts, surplus manure in nitrate-vulnerable zones is frequently divided into a liquid and solid fraction. Managing the liquid fraction (LF) typically presents a greater challenge due to its substantial volume. This study aimed to assess the environmental impacts by region and trade-offs of managing surplus LF with inventory data from pilot facilities using a life cycle assessment (LCA). The LF-treatment technologies assessed were (i) nitrification-denitrification (NDN) with field application of effluent (ii) NDN with ammonia stripping and nitric acid scrubbing as a pre-treatment step followed by polishing in constructed wetlands, and (iii) nutrient up-concentration using vacuum evaporation and/or membrane filtration. The LCA results suggested that 60 to 80 % of the environmental impacts occurred locally. Nutrient up-concentration from LF via membrane filtration (reverse osmosis) and vacuum evaporation indicated a better environmental performance, albeit with high uncertainty when compared to the other scenarios. Although ammonia stripping-scrubbing showed environmental benefits, these were offset by high environmental burdens from fugitive N2O emissions and energy demand during NDN. Furthermore, the study identified that managing the effluent after NDN, a source of potassium (K), requires a nuanced approach from policymakers. Firstly, when K fertilization requirements are not met, direct land application of the effluent as a fertigation source can be a viable option. This minimizes the need for synthetic K fertilizer production and its ensuing freshwater ecotoxicity impacts. However, tertiary treatment of NDN effluent via constructed wetlands can be considered to prevent deterioration of soil from the influx of K. Policymakers are encouraged to engage with local stakeholders to tailor solutions based on these trade-offs. Furthermore, future research should focus on the implications of K on soil quality as well as the life span of nutrient up-concentration technologies for LF.

Nitrate Vulnerable Zones (NVZs) are faced with a surplus of animal manure due to intensive livestock production, and the high use of mineral nitrogen (N) fertilisers in crop production. Recovery of N from animal manure to replace synthetic mineral fertilisers is considered a key strategy to close the N loop for more sustainable agriculture and to meet strict legal frameworks. In this study, N recovery from swine wastewater by an ammonia (NH3) stripping process followed by purification via an aerated constructed wetland (ACW) was proposed as an alternative approach to conventional systems based on biological nitrification-denitrification (NDN) treatment. The performance of the NH3 stripping pilot as well as the ACW was monitored in 2019–2020 over three periods, to evaluate the quality of recovered ammonium nitrate (AN) solution and the effluent of the ACW. Results showed that the NH3 stripping unit recovered 21% of total-N (32% of mineral-N) in the form of AN solution. This could be used as a mineral fertiliser according to the criteria of the European Fertilising Products Regulation 2019/1009 and the technical proposal of manure-derived RENURE (REcovered Nitrogen from manURE) products by the European Joint Research Centre. As a RENURE product, AN solution would reach an end-of-manure status and could be used as a synthetic N fertiliser replacement. The tested ACW achieved a high removal efficiency with respect to suspended solids (96%), biological oxygen demand (96%), chemical oxygen demand (90%), total-N (80%), and total phosphorus (97%). The quality of ACW effluent was comparable to that of NDN treatment. Though the overall cost of the proposed pilot-scale process consisting of NH3 stripping (5.1 € t−1) and ACW (12 € t−1) was calculated slightly higher than conventional NDN treatment (16 € t−1), it is foreseen to outcompete at a higher loading rate (over 45 m3 ha−1 d−1). Furthermore, post-purification will be needed for the ACW effluent to meet the requirements for discharge to surface water.

Resource-efficient nitrogen management is of high environmental and economic interest, and manure represents the major nutrient flow in livestock-intensive regions. Ammonia stripping/scrubbing (SS) is an appealing nitrogen recovery route from manure, yet its real-life implementation has been limited thus far. In nutrient surplus regions like Flanders, treatment of the liquid fraction (LF) of (co-)digested manure typically consists of nitrification/denitrification (NDN) removing most N as nitrogen gas. Integrating SS before NDN in existing plants would expand treatment capacity and recover N while maintaining low N effluent values, yet cost estimations of this novel approach after process optimisation are not yet available. A programming model was developed and calibrated to minimise the treatment costs of this approach and find the balance between N recovery versus N removal. Four crucial operational parameters (CO2 stripping time, NH3 stripping time, temperature and NaOH addition) were optimised for 18 scenarios which were different in terms of technical set-up, influent characteristics and scrubber acid. The model shows that SS before NDN can decrease the costs by 1 to 56% under optimal conditions compared to treatment with NDN only, with 1 to 8% reduction for the LF of manure (22-29% recovered of N treated), and 11 to 56% reduction for the LF of co-digested manure (42-67% recovered of N treated), primarily dependent on resource pricing. This study shows the power of modelling for minimum-cost design and operation of manure treatment yielding savings while producing useful N recovery products with SS followed by NDN.

In this paper, we performed technology assessment and systems analysis of primary digestate processing techniques to provide a comprehensive analysis of their environmental and cost performance. We compiled more than 100 observations from large-scale biogas plants and considered digestate based on manure, crops and agro-wastes, and food waste under the geographical contexts of Sweden and Belgium. Centrifuge, screw press, and rotary drum were identified as suitable primary processing techniques. We analyzed the climate impact, energy use, and operational cost of digestate management under these scenarios: no processing, partial processing (solid–liquid separation) and full processing (solid–liquid separation followed by ammonia stripping). As expected, the suitable digestate processing varied with the context, transport was often the most critical cost factor, and emissions from storage reduced the climate savings from the use of biofertilizers. However, treating liquid fraction became a main contributor to cost and climate impact under the Belgian conditions. Consequently, the possibility for local application of liquid fraction as biofertilizer could prevent costs and impacts associated with its further treatment. The main novelty of this work is in its integrative and comprehensive approach toward the choices and impacts of primary processing of digestate. We tried to bridge many individual case studies, drew from experiences of biogas plants in different geographical contexts, assessed suitable processing techniques for different digestate types, and analyzed the environmental impacts and cost of digestate management from a life cycle perspective. We believe that such integrated approaches would help decision-making for increased sustainability of the biogas sector.

The application of animal manure on agricultural land in the Netherlands is bound by legal limits to prevent the leaching of nitrogen (N) and phosphorus (P) to ground and surface waters. The surplus of animal manure is transported abroad at high costs. In this study, a full-scale cascaded membrane filtration system (GENIUS) comprising two decanter centrifuges, microfiltration (MF) reverse osmosis (RO) and an ion exchanger was monitored. The system processed agricultural digestate from anaerobically co-digested animal manure into two solid fractions (SFs), RO concentrate, MF concentrate and purified water. The goal was to separate P and ammoniacal nitrogen (NH4-N) and remove water from the digestate. From the initial digestate, 66% of P was recovered in the first SF, which constituted 15% of the total mass, without the addition of iron or aluminium salts or polymer flocculants. Another 29% of P was recovered in the MF concentrate and used as a liquid organic fertiliser. Of the P in the initial digestate, 98% was removed before RO. For N, 34% ended up in the RO concentrate and this product can be regarded as an alternative for synthetic N fertiliser as it contains N solely in mineral form. Overall, around 18% of the total mass of initial digestate was discharged as purified water and 31% was locally applied in the form of RO concentrate. We found that aqua regia digestion before chemical analysis can decrease the measured S content of processed digestate. Compared to the transport of raw (unprocessed) digestate, the implementation of the GENIUS system led to a 53% reduction in the mass-weighted average transport distance.

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

The information compiled in this report is divided over 5 chapters.Introduction is given in Chapter 1.Chapter 2 focuses on characterisation of products collected and analysed from five SYSTEMIC demo plants.The characterisation complies information on macronutrients, micronutrients and heavy metals.In 2020, the monitoring was extended with analysis of organic pollutants (residues from pesticides, herbicides and pharmaceuticals).The content of nutrients in digestate varied between different biogas installations, according to the type and composition of processed feedstock, and biogas process conditions (e.g.organic loading rate, hydraulic retention time, temperature).Moreover, product characterisation has confirmed that application of NRR technology changes the initial composition of the treated digestate and upconcentrates nutrients in the recovered products.The number of compounds (herbicides, pesticides, and pharmaceuticals) detected varied between the plants and can be related to the feedstock of the plant.Residues of pharmaceutically active compounds were detected in digestate of AD plants where animal manure is part of the ration.However, no residues of pharmaceuticals were detected in digestate obtained by thermophilic digestion of sewage sludge.Finally, no residues were detected in purified water or ammonium sulphate solution.Chapter 3 covers nine experiments which are reported in the form of extended abstracts: as certain experiments have been published in peer-review scientific journals or are currently under review or under preparation for submission to peer-review scientific journal.The first two experiments deal with assessment of nitrogen (N) and carbon (C) mineralisation rates of raw digestate (section 3.1) and solid fraction (SF) of digestates (section 3.2) from SYSTEMIC demo plants.For raw digestates, results showed that N release and mineralisation were significantly positively correlated with the initial NH 4 + -N:total N ratio of the products and negatively correlated with total C:total N. The N mineralisation was observed for all products and humifiable fraction of C ranged from 50 to 81% for raw digestates, suggesting that these materials could be suitable candidates to increase C storage in agricultural soils.For SFs, the various SFs showed similar patterns of C mineralisation and it was concluded that the nature of the organic matter (OM) was the main factor controlling C mineralisation in the different treatments.In terms of N, some SFs may cause temporary N immobilisation.

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.

The research was undertaken as part of the project called SYSTEMIC: ‘Systemic large scale eco-innovation to advance circular economy and mineral recovery from organic waste in Europe’. This project has received funding from the European Union’s H2020 research and innovation programme under the grant agreement No: 730400. SYSTEMIC started on 1 June 2017 and continued for 4 years. A full list of all end products is available at www.systemicproject.eu. The SYSTEMIC project was coordinated by Oscar Schoumans (oscar.schoumans@wur.nl) and Inge Regelink (inge.regelink@wur.nl) from Wageningen Environmental Research. The NRR process consist of two independent NRR systems. In the GENIUS system, digestate is first separated into a solid (SF) and a liquid fraction (LF) of digestate by a decanter centrifuge. The SF of digestate is subsequently processed by the RePeat system. The RePeat system separates the P from the organic matter through leaching with water and sulphuric acid. Two sequential leaching steps remove in total 70–90% of the P present in the ingoing digestate, thereby producing a low-P soil improver. The dissolved P subsequently precipitates through addition of lime (Ca(OH) 2 ) or magnesium hydroxide (Mg(OH) 2 ), thereby producing precipitated P salts . Part of the sulphate, which was added as sulphuric acid, precipitates with calcium as gypsum. The gypsum partly ends up in precipitated P salts and partly in a separated organic gypsum-rich sludge which can be used as fertiliser. Water is continuously reused within the process, thereby preventing the creation of a waste stream. The LF of digestate is further processed by the rest of the GENIUS system: a second decanter centrifuge, a microfiltration (MF) unit, two RO units placed in series and ion exchangers. The following end products are thereby produced: RO concentrate, rich in N and potassium (K), purified water and a blend of the SF of the second decanter centrifuge and MF concentrate.

Biological ammonia (NH3) stripping and scrubbing results in the production of chemical building blocks suitable for the production of marketable biobased fertilizers or other chemical products. This chapter deals with NH3 stripping and scrubbing processes for recovery of mineral nitrogen. It discusses different configurations for the recovery of NH3 as air scrubber water from waste air and effluent streams, mainly focusing on livestock production and anaerobic digestion. The chapter provides a brief overview of a variety of chemicals (organic acids, nitric acid, and gypsum) that have been investigated as alternatives to H2SO4 in order to capture NH3 in scrubbing towers. It examines successful full-scale applications of NH3 recovery from different waste origins. The chapter also looks at the quality characteristics of the recovered ammonium sulfate or ammonium nitrate.

Development and optimization of nutrient recovery technologies for agricultural waste is on the rise. The full scale adoption of these technologies is however hindered by complex legal aspects that result from lack of science-based knowledge on characterization and fertilizer performance of recovered end-products. Ammonium sulfate (AS) and ammonium nitrate (AN), end-products of (stripping-)scrubbing technology, are currently listed by the European Commission as high priority products with the potential of replacing synthetic N fertilizers. The legal acceptance of AS and AN will be highly dependent on critical mass of scientific evidence. This study describes four different (stripping-)scrubbing pathways to recover ammonia with an aim to (i) assess product characteristics of ammonium nitrate (AN) and ammonium sulfate (AS) produced from different installations, (ii) evaluate fertilizer performance of recovered end-products in greenhouse (Lactuca sativa L.) and full field (Zea mays L.) scale settings and (iii) compare the observed performances with other published studies. Results have indicated that the recovered products might have a different legal status, as either mineral N fertilizer or yet as animal manure, depending on the used (stripping-)scrubbing process pathway. Nevertheless, no significant differences in respect to product characterization and fertilizer performance of AN and AS have been identified in this study as compared to the conventional use of synthetic N fertilizers. This indicates that recovered AS and AN are valuable N sources and therefore might be used as N fertilizers in crop cultivation.

A novel acidotolerant and moderately thermophilic sulfur-reducing bacterium was isolated from sediments of the Tinto River (Spain), an extremely acidic environment. Strain TR1T stained Gram-negative, and was obligately anaerobic, non-spore-forming and motile. Cells were short rods (1.5-2 × 0.5-0.7 μm), appearing singly or in pairs. Strain TR1T was catalase-negative and slightly oxidase-positive. Urease activity and indole formation were absent, but gelatin hydrolysis was present. Growth was observed at 20-52 °C with an optimum close to 50 °C, and a pH range of 3-7 with optimum between pH 6 and 6.5. Yeast extract was essential for growth, but extra vitamins were not required. In the presence of sulfur, strain TR1T grew with acetate, formate, lactate, pyruvate, stearate, arginine and H2/CO2. All substrates were completely oxidized and H2S and CO2 were the only metabolic products detected. Besides elemental sulfur, thiosulfate was used as an electron acceptor. The isolate also grew by disproportionation of elemental sulfur. The predominant cellular fatty acids were saturated components: C16 : 0, anteiso-C17 : 0 and C18 : 0. The only quinone component detected was menaquinone MK-7(H2). The G+C content of the genomic DNA was 34 mol%. The isolate is affiliated to the genus Desulfurella of the class Deltaproteobacteria, sharing 97 % 16S rRNA gene sequence similarity with the four species described in the genus Desulfurella. Considering the distinct physiological and phylogenetic characteristics, strain TR1T represents a novel species within the genus Desulfurella, for which the name Desulfurella amilsii sp. nov. is proposed. The type strain is TR1T ( = DSM 29984T = JCM 30680T).