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.

This deliverable contains the outcomes of our exploitation task in the project Circular Agronomics. Five technologies, namely solar drying, microfiltration, vacuum degasification, K struvite recovery and membrane treatment had been transferred to a potential replication site and been evaluated under these large-scale conditions. The studies consider a site description, the integration of technology into the site, a cost estimation, a forecast on emissions, legal aspects to be considered and finally some conclusions on roll-out and/or further technology development. To date the technologies reached TRL 6 or 7 and are applied to solid or liquid fraction of agricultural digestate or wastewater and waste streams from food industry. The scale of installations varies from concept studies for a capacity less than 1 m³/h towards 15 m³/h resulting in different cost profiles. A cross-cutting conclusion on different influencing factors such as technology readiness, their environmental benefits, their cost sufficiency and political factors influencing potential replication is delivered. The final paragraph of each concept study concludes with the recommendations for technology provider and or site owner in terms of further development and provides answers about uncertainties in terms of investment decisions. A further synthesis of the main finding of this work will be published in Deliverable 6.9 - a brochure about the technologies.

Ein Ziel des Horizon 2020 geförderten Projekts Circular Agronomics ist die Reduktion von stickstoffbasierten Emissionen durch die landwirtschaftliche Anwendung von Gärresten. Dafür werden verschiedene Pilotverfahren erprobt. Um das Konzept der Vakuumentgasung von Gärresten zu verifzieren, wurde eine Containeranlage in Berge (Nauen, BRB) mittels sieben Batchversuchen in Betrieb genommen. Der Gärrest stammte aus gemischter Vergarung. Unterschiedliche  Zusammensetzungen der Betriebsparameter Temperatur, Volumenstrom des Strippgases,pH-Wert und Absolutdruck wurden getestet um den Einfluss auf die Eliminationsrate von TAN zu untersuchen. Daneben wurden neben weiteren die Parameter KS,4,3, Leitfähigkeit und pH dokumentiert um Veränderungen auf das Puffersystem des Gärrests zu ermitteln. Um den Prozess zu zukunftig zu optimieren, wurde der allgemeine Anlagenbetrieb beobachtet. Bei 70 °C, 310 mbar pabs, pH 9 und einem Strippgasstrom von 3,1 m3 · h−1 konnten aus 40 L Gärrest in 90 min 94,6 % des TAN eliminiert werden, während die Elimination bei 35 °C nur 31,6 % betrug. Vorangehendes Strippen von CO2 bei 70 °C, 800 mbar pabs und einem Strippgasstrom von 3,1 m3 · h−1 konnte die benötigte Menge NaOH (50 %) von 6 mL · L−1 auf 3,2 mL · L−1 nach 30 min und 1,7 mL · L−1 nach 60 min absenken. Der Prozess könnte eine vielversprechende Alternative zur konventionellen Luftstrippung darstellen. Er hat Vorteile gegenüber alternativer Methoden wie Membranfiltration oder Ionenaustausch, da es keiner exzessiven Vorbehandlung des Gärrests bedarf. Zukünftig müssen einige bauliche Änderungen vorgenommen werden, um den kontinuierlichen Betrieb und die Rückgewinnung von Ammoniak in der Pilotanlage zu ermöglichen.