Valorization of Industrial Residue Streams in a Circular Economy Framework: Zero-Waste Nutrient Recovery and Biorefinery Integration
Author
Hernandez de la Torre Lopez, Jose
Term
4. term
Education
Publication year
2026
Abstract
The transition towards a circular bioeconomy is vital for more sustainable industrial production, and this thesis investigates how residue streams from enzyme manufacturing can be integrated into such a framework. In collaboration with Novonesis, a protein-rich side stream from enzyme production is analysed as part of a broader bioconversion concept that aims to transform it into polyhydroxyalkanoates (PHA), a biodegradable bioplastic with thermoplastic properties. A critical intermediate step in this process is the purification and concentration of volatile fatty acids (VFA) from a complex mixture containing nitrogen sources and other nutrients. The study characterizes the original residue stream and develops a synthetic feed solution based on this analysis. Nanofiltration is selected as the separation technology according to process requirements and practical availability, and experiments are carried out at different transmembrane pressures, pH values and membrane types to explore their influence on flux, solute rejection and fouling. The obtained data are constrained by experimental limitations and mainly confirm previously reported trends, indicating that additional tests at other pressures and with the actual industrial stream are needed. Furthermore, numerical tools are developed to calculate fouling rates, dissociation fractions, time-discretized changes in composition and membrane performance, which can support scaling and future optimization once more extensive experimental data become available.
Overgangen til en cirkulær bioøkonomi er central for mere bæredygtig industriel produktion, og denne afhandling undersøger, hvordan reststrømme fra enzymproduktion kan indgå i en sådan ramme. I samarbejde med Novonesis analyseres et proteinrigt sidestrøm fra enzymfremstilling, som i et overordnet biokoncept skal omdannes til polyhydroxyalkanoater (PHA), en bionedbrydelig bioplast med termoplastiske egenskaber. Et kritisk mellemtrin i denne proces er oprensning og opkoncentrering af flygtige fedtsyrer (VFA) fra en kompleks blanding af kvælstofkilder og andre næringsstoffer. Studien karakteriserer den oprindelige reststrøm og udvikler en syntetisk fodringsopløsning baseret på denne analyse. Nanofiltrering vælges som separationsmetode ud fra proceskrav og tilgængelige ressourcer, og der gennemføres forsøg med forskellige transmembrantryk, pH-værdier og membrantyper for at undersøge effekter på flux, tilbageholdelse og fouling. Resultaterne er begrænsede af eksperimentelle forhold og bekræfter primært tidligere fund, hvilket peger på behov for yderligere forsøg ved flere tryk og med den reelle reststrøm. Der udvikles desuden numeriske værktøjer til at beregne foulinghastigheder, dissociationsgrader, tidsskridt-baserede sammensætningsændringer og membranperformance, som kan anvendes til skalering og videre optimering, når der foreligger mere omfattende forsøgsdata.
[This abstract has been generated with the help of AI directly from the project full text]