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Publisher DOI: 10.1186/s13705-015-0057-5
Title: Biogas and nutrients from blackwater, lawn cuttings and grease trap residues : experiments for Hamburg’s Jenfelder Au district
Language: English
Authors: Hertel, Saskia 
Navarro, P. 
Deegener, Stefan 
Körner, Ina 
Keywords: blackwater;grease trap residues;lawn cuttings;lawn juice;anaerobic digestion;biogas;bioresources;inventory;fertilizer;nutrient recovery;digestate utilization;Hamburg;Jenfelder Au
Issue Date: 21-Sep-2015
Publisher: SpringerOpen
Source: Energy, Sustainability and Society 1 (5): (2015)
Journal or Series Name: Energy, Sustainability and Society 
Abstract (english): Background: The project KREIS focuses on a new combination of renewable energy provision with innovative wastewater treatment, called the “Hamburg Water Cycle®” (HWC) which will be applied in Hamburg’s neighbourhood Jenfelder Au. HWC includes a separate collection of rainwater, greywater and blackwater. Vacuum toilets are used to concentrate the blackwater. Biogas will be produced from the blackwater in an anaerobic digestion process together with co-substrates. The blackwater will be transported to the anaerobic pre-treatment facility via a vacuum system. Construction of water systems started in 2013, and commercialization of houses is planned to be finished in 2018. Methods: The article focuses on research work accompanying the demonstration project. Blackwater and the co-substrates, lawn cuttings and grease trap residues from restaurants and canteens will be considered as bioresources, not as residues. To evaluate the utilization efficiency, three investigation steps were carried out: inventory to determine substrate quantities and qualities, anaerobic digestion to determine biogas production, and evaluation of digestate utilization options. Results: The daily amount of blackwater in Jenfelder Au is calculated to be about 12 m3 (dry matter (DM) 0.6 %; organic dry matter (oDM) 65 % DM; nitrogen (N) 28 % DM; phosphorus (P) 2.7 %). To increase the biogas production, co-substrates will be added. Grease trap residues (averages: DM 2 %; oDM 85 % DM; N 2.5 % DM; P 0.6 % DM) and lawn cuttings (averages: DM 30 %; oDM 80 % DM; N 2.6 % DM; P 0.3 % DM) were selected. The inventory study showed a sufficient potential of lawn cuttings within a 5-km radius. The lawn cuttings must be pre-treated for wet fermentation. Two options were investigated: press juice preparation and wet shredding of the fresh and silage lawn. Batch test was used to determine the biogas potential of the substrates with the following average results: blackwater 500 nl/kg oDM, grease trap residues 1000 nl/kg oDM, lawn cuttings 400 nl/kg oDM and lawn juice 500 nl/kg oDM. The effects of the composition of the substrate mixture and of the retention time in the reactor on biogas quantity and process stability were studied in semi-continuous operating reactors. Experiments showed that a stable process with an average biogas production of 800 nl/kg oDM is, e.g., possible with a mixture of blackwater, press juice of lawn cuttings and grease trap residues in a fresh mass ratio of 1:1:1. Furthermore, the N and P contents in digestates were determined. These nutrients are valuable for fertilization. Conclusion: It has been shown that blackwater combined with local waste streams can be used for biogas generation and that it has a potential as fertilizer. The experiments have shown that co-digestion has a positive effect on biogas yields and lawn cuttings are suitable as co-substrate. Lawn cuttings can be applied as lawn juice or lawn suspension. Ways of an integral utilization and the potential of nutrient recovery are shown in this work.
DOI: 10.15480/882.1607
ISSN: 2192-0567
Institute: Abwasserwirtschaft und Gewässerschutz B-2 
Type: (wissenschaftlicher) Artikel
Funded by: Projektträger Jülich (PTJ) and the Federal Ministry of Education and Research (BMBF).
Project: KREIS-Projekt (Kopplung von regenerativer Energiegewinnung mit innovativer Stadtentwässerung) 
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