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.

Kabbe, C. , Kraus, F. (2022): Phosphor – Von der Rückgewinnung zum Recycling (Praxishandbuch der Kreislauf- und Rohstoffwirtschaft 2., überarbeitete und aktualisierte Auflage).

In: Praxishandbuch der Kreislauf- und Rohstoffwirtschaft 2., überarbeitete und aktualisierte Auflage, edited by Peter Kurth, Anno Oexle and Martin Faulstich


Die traditionell vielschichtige Abfallwirtschaft entwickelt sich mit der ihr eigenen Dynamik zur Kreislauf- und Rohstoffwirtschaft. Im vorliegenden Handbuch werden erstmalig alle wesentlichen Aspekte dieses Wirtschaftssektors – fachübergreifend und interdisziplinär – behandelt. Neben den in der Ressourcenwirtschaft relevanten rechtlichen Fragestellungen (u. a. Stoffrecht, Verwaltungsrecht, Haftung und Transport) sind die unterschiedlichen Stoffströme dargestellt (z. B. Glas, Papier, Verpackung, Metalle und Elektronik-Altgeräte, Bioabfälle) sowie Anlagentechnik und Logistik beschrieben (Abfallwirtschaftssysteme, Abfallbehandlung, Deponierung). Bei der Auswahl der Themen und Autoren lag der Schwerpunkt auf Praxisrelevanz und Praxisbezug.

ISBN: 978-3-658-36261-4

Kraus, F. (2022): Aktueller Stand beim Phosphorrecycling.

Karlsruhe Tagungsband der 33. Karlsruher Flockungstage 2022. Karlsruher Institut für Technologie (KIT)- Die Forschungsuniversität in der Helmholtz-Gemeinschaft

Grassauer, F. , Herndl, M. , Iten, L. , Stüssi, M. , Harder, R. , Gaillard, G. , Kraus, F. (2022): D5.2. Environmental profile of agro-ecosystems and of the food value chain.

Hoehere Bundeslehr-Und Forschungsanstalt Fuer Landwirtschaft Raumberg-Gumpenstein


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.


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.

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