Technologies for resource recovery from human urine: terrestrial and space applications

Abstract of the doctoral research:

On earth, mineral fertilizers are extensively produced and inefficiently used. Tremendous losses on the fields result in economic costs and the deterioration of the environment. In long-term space missions, on the other hand, nitrogen is often scarce and therefore valuable. In both cases, nitrogen recycling and valorisation from concentrated waste streams, such as human urine, can tackle these issues.
Urine can be separately collected at the toilet. Prone to microbial growth, urine is highly unstable resulting in NH3 release, but also loss, odor nuisance, and scaling of source separation infrastructure and downstream valorisation technologies. Therefore, controlled urine hydrolysis and thus stabilisation in a reactor in the toilet was found to resolve these issues. Inoculation with autofermented urine would be sufficient for rapid start-up. In space, direct filtration would be more suitable.
Two novel technologies were developed for nitrogen valorisation. One strategy is to extract ammonium from urine directly via electrochemically assisted membrane stripping, resulting in an ammonia liquid, free of urine-derived microorganisms and micropollutants. This can be used as a feed source for the production of microbial biomass, rich in protein. By applying this biomass as a feed additive, the need to grow feed crops on agricultural land with mineral fertilizer reduces.
Another strategy relies on microorganisms converting the nitrogen into nitrate. This can then be used in closed loop systems, e.g. in space, as a liquid fertilizer for plant growth on site. Space conditions, however, require a fully known (‘gnotobiotic’) microbial community. A synthetic consortium was established and proven to nitrify urine in a long-term continuous reactor, producing a sterile nitrate effluent.
The implementation of both technology concepts in (extra)terrestrial applications allows to replace inefficient and costly nitrogen usage with nitrogen recovery.

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Dissertation Supervisors:

Prof. Dr. Ir. Korneel Rabaey & Prof. Dr. Ir. Siegfried Vlaeminck

 

Event location: 
Aula of Ghent University, Voldersstraat 9, 9000 Gent
Event date: 
Monday, 3 December, 2018 - 17:00
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