This report summarises the theoretical design of a degasification plant to recover ammonia and carbon dioxide from organic residues, such as agricultural digestates, manure and municipal/industrial wastewater. Heat and water management had been identified as one crucial factor to optimise during this research. The chemical and physical parameters reveal the high tendency of ammonia towards water phase and underline the difficulty in ammonia stripping. Besides temperature, the volumetric gas-liquid ratio had been identified as most important factors. Regarding pH-value it had been observed, that a further increase is not sufficient once pH 9 is reached. Applied absolute pressure also has been identified of lower importance, compared to temperature and volumetric gas-liquid ratio. The latter three parameters are influencing evaporation and heat management in the desorption stage. A design model from literature according to Onda showed good correlation with the practical experiments including packings. Other column fillings as cones lead to operational problems. The understanding of the exact relations in column design are further used to design a cost-efficient process with low carbon footprint. The practical tests, as such, were reproducible, however the batch operation and limitations in the column design resulted in a limited transferability towards large scale plants. In terms of the absorption stage, the pilot needs to be further optimised to reach sufficient recovery rates. An absorption of ammonia and carbon dioxide under use of gypsum is favoured to also recover carbon dioxide and to avoid sulfuric acid dosing. In that term further tests and optimisation is needed, to have a fully quantifiable pilot system. The integration of a measure-control system is a further development step. In conclusion, the degasification process with low pressure (vacuum) reveals benefits compared to conventional air stripping in terms of heat management and the necessary gas-liquid-ratio, which has effects on column diameter and eventually column height. The necessity of aggressive chemicals dosage (as caustic in desorption) or acid (in absorption) is in view of the authors not given, hence cheap and safe alternatives (e.g. CO2 stripping) and gypsum dosage as alternative sulphur source work sufficient.

Agriculture, and in particular livestock, uses nutrients inefficiently, contributing to water and air pollution and global warming. One of the objectives of the Green Deal of the European Commission (EC), through the Farm to Fork strategy, is the reduction of nutrient losses by at least 50% while ensuring the soil fertility. The EC expects that this will reduce the use of fertilisers by at least 20% by 2030. Integrated nutrient management plans will be developed by Member States with the objective of reducing and preventing further pollution from excessive use of fertilisers, while encouraging nutrient recycling from organic waste as fertilisers. At the same time, the EC encourages increasing information to consumers through harmonised labelling and establishes targets to reduce food waste.

Circular Agronomics aims to convert agriculture into a more circular and sustainable sector through short- and long-term measures from practical innovations to costumer awareness and facilitating legislation. With many of the developed innovative solutions a significant reduction of nitrogen emissions, in particular ammonia (NH3), was achieved. Besides, the harmful greenhouse gas (GHG) nitrous oxide (N2O, almost 300 times the Global Warming Potential as carbon dioxide over 100 years) was reduced significantly (e.g. >75 % due to fertiliser reduction in the trials with N efficient genotypes of winter wheat). Results are very promising for a transition to an environment- and climate-friendly agriculture, when farmers are able to invest in such innovations and build up the necessary knowledge. At the same time, consumers need transparent product labelling to make the right decision based on their norms.

Durch eine mehrstufige Behandlung von Biomasse unter Luftabschluss, kommt es in Biogasanlagen zur Produktion von Biogas. Als Nebenprodukt entstehen dabei ebenso Biogasgärreste, welche durch die stoffliche Zusammensetzung hochwertiges Düngemittel darstellen. Eine verbesserte Gärrestenutzung kann zur Steigerung des Nährstoffmanagements führen. Der wichtigste Nährstoff für Nutzpflanzen ist Stickstoff. Deshalb macht es Sinn Ammoniumstickstoff aus Abwässern, Gülle und anderen Gärresten zurückzugewinnen. Eine Möglichkeit ist die sogenannte AmmoniakStrippung. In der Nachbehandlung wird Ammoniumstickstoff in einem Gaswäscher erneut aufkonzentriert und somit das Ammoniak in wieder verwertbarer Form zurückgewonnen. Um die Inbetriebnahme eines Gaswäschers zu realisieren, wurde ein Messprogramm erstellt. Durch sieben Versuchsreihen und einer Variation von Stellparametern wurden zunächst die Eliminationsraten in einer Stripp-Kolonne betrachtet. Des Weiteren wurde die Anreicherung im Gegenstromverfahren durch absorptive Prozesse von Ammoniumstickstoff und Kohlenstoffdioxid in einem Gaswäscher bilanziert und durch Gegenüberstellung der Verfahren Auswertungen hinsichtlich der quantitativen Rückgewinnung erzielt. Außerdem wurde als Optimierungsoption eine theoretische Kolonnenauslegung betrachtet. Der Schwerpunkt lag dabei auf der Bestimmung der Füllkörperhöhe und des nassen Druckverlusts. Weiterhin wurden auf Basis dieser Ergebnisse Untersuchungen zu unterschiedlichen Füllkörpermaterialien durchgeführt.

Um die Trennleistung einer Vakuumentgasungsanlage zu optimieren, wurde mit dem Einsatz von Füllkörpern der Ammoniumstickstoffanteil von separiertem Gärrest im Gegenstromverfahren mit Strippluft abgereichert. Drei Füllkörperarten unterschiedlicher Hersteller wurden bei gleichen Betriebsbedingungen untersucht. Die Effizienz konnte so bei einer stabilen Prozessführung gesteigert werden. Außerdem wurde eine theoretische Kolonnenauslegung durchgeführt, die die Bestimmung der Füllkörperhöhe und des nassen Druckverlusts umfasste. Aus diesen Ergebnissen lassen sich Vorhersagen hinsichtlich der Ausgangskonzentrationen von Ammoniumstickstoff prognostizieren. Aus den Experimenten und der theoretischen Kolonnenauslegung konnte eine optimierte Anlagenkonfiguration abgeleitet werden.

Technical nitrogen (N) recovery from biogas digestate via vacuum degasification (VD) of ammonia is an important task with regards to environmental issues and economic reasons. There has not yet been much research on VD, but compared to conventional stripping methods energy costs might be reduced. In the frame of the EU project ”Circular Agronomics” a VD pilot plant for N recovery from biogas digestate was built. This study aims on optimizing the pilot plant with special regards to the scrubber, where the N fertilizer is formed. The plant was operated at 310 mbar absolute pressure, 150 L · h−1 recirculation rate and 35 kg total water mass. Two different conditions were examined: condition 1) 70◦C, gas to liquid ratio (G/L) 20:1, pH 9 and condition 2) 50◦C, G/L 33:1, pH 10. A total ammonium nitrogen (TAN) elimination of 93% for condition 1 and 73% for condition 2 was achieved. Conducting the experiments a high amount of water was evaporated (25% for condition 1 and 5% for condition 2). The high water evaporation leads to a low TAN/water ratio in the gas stream of 0.4−1.2 (condition 1) and 1.6−2.8 mol · L−1 (condition 2) respectively. A low TAN/water ratio is disadvantageous, as it results in a dilution of the N fertilizer, that is being formed in the subsequent scrubber. Besides, it was found, that the plant loses high amounts of energy in form of latent heat due to water evaporation and requires more favorable energy recovery.

Satisfying the ever-growing global food demand was traditionally done by expanding and intensifying agricultural production. However, these practices led to considerable environmental impacts as the food value chain nowadays accounts for considerable amounts of greenhouse gas emissions (26 % of global anthropogenic emissions) and eutrophication (78 % of global emissions). Therefore, the project Circular Agronomics aims at the assessment of practical and technical solutions to improve the current carbon (C), nitrogen (N), and phosphorus (P) cycling in European agro-ecosystems and related up- and downstream processes within the food supply chain. The project comprises six case studies from different regions in the European Union (i.e., Catalunia, Spain; Brandenburg, Germany; Lungau, Austria; Emilia-Romagna, Italy; Gelderland, Netherlands; South Moravia, Czech Republic) that planned to conduct ten different experiments in order to test the practical and technical solutions by either a combination of a technical sub-system with a subsequent agricultural field experiment or a sole agricultural field experiment. However, different restraints led to waiver or postponement of certain traits of some experiments. Therefore, the data collection only yielded seven experiments with complete data. Regarding the other three experiments, at least data on the respective technical sub-systems could be collected. The experiments were subsequently assigned to three innovative strategies which aim at different compartments of agricultural production (i.e., (1) nutrient management in crop production, (2) nutrient management in livestock production, (3) and waste management and nutrient/carbon recovery). The different experiments were analyzed according to their respective system description and in compliance with the methodology as outlined in Deliverable 5.1. Moreover, abiotic resource depletion was added as an environmental impact category due to its relevance for experiments that focus on mineral fertilizer as impacts from background processes such as mining. The strategy of nutrient management in crop production comprised three experiments that investigated different management parameters to increase the nutrient efficiency in crop production. The results show that increasing levels of N fertilization leads to higher yields and increases emissions (abiotic resource depletion and eutrophication), which is even more pronounced under a dry climate. Regarding the timing of fertilization, four weeks after sowing showed the least emissions, which can be explained by the higher N demand of the plants at this stage. Moreover, the test of different tillage regimes indicated the no-tillage variant to be favorable in terms of environmental impacts per kg crop. Results of two experiments assigned to the innovative strategy of nutrient management in livestock production showed the beneficial effects of precision feeding in terms of mitigating greenhouse gas emissions and eutrophication due to a needs-oriented supply of nutrients that leads to lower losses. It could further be shown that the extensive management of organic dairy farms can be very efficient in terms of eutrophication if the management intensity matches the natural production potential of the agricultural area of the farm. The remaining five experiments examined improvements in waste management and carbon/nutrient recovery by using waste streams as potential sources of nutrients or reducing emissions by capturing nutrients. Regarding three investigated digestate treatment concepts, microfiltration/ microsieving revealed the lowest environmental impacts. Regarding capturing nutrients, the struvite technology can recover and subsequently recycle these nutrients in a comparably clean and plant available form from soybean wastewater treatment with low environmental impacts. The membrane technology seems to be an electricity-saving alternative compound for whey thickening compared to centrifuges. Overall, it could be shown that the innovative technical sub-systems cause additional efforts (such as electricity consumption) and corresponding additional impacts. However, the subsequent farming systems should be able to achieve reduced emissions. Regarding the non-renewable energy demand and global warming potential of the observed systems, it seems rather unlikely that a corresponding reduction in emissions by farming systems can be realized. Conversely, it is more likely that this trade-off can be achieved for acidification and eutrophication (especially ammonia emissions), where agriculture has a crucial role. The report shows particular areas of improvement for process engineers focusing on optimization of technologies and farmers/agricultural researchers for optimization of their nutrient management behaviors. From the comparison, particular done for one experiment and separated assessments done for others and incomplete data-sets for several technical and farming systems, we only can state that such a hybrid out of technology and agriculture may reduce environmental impacts if it is well applied, however there it is unlikely that it is always well applied. Nonetheless, this aspect of dedicated nutrient management and emission mitigation should be investigated further.