Options
Biogas and nutrients from blackwater, lawn cuttings and grease trap residues : experiments for Hamburg’s Jenfelder Au district
Citation Link: https://doi.org/10.15480/882.1607
Publikationstyp
Journal Article
Date Issued
2015-09-21
Sprache
English
Author(s)
TORE-DOI
Volume
5
Issue
1
Start Page
29
Citation
Energy, Sustainability and Society 1 (5): (2015)
Publisher DOI
Scopus ID
Publisher
SpringerOpen
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.
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.
Subjects
blackwater
grease trap residues
lawn cuttings
lawn juice
anaerobic digestion
biogas
bioresources
inventory
fertilizer
nutrient recovery
digestate utilization
Hamburg
Jenfelder Au
DDC Class
620: Ingenieurwissenschaften
Publication version
publishedVersion
Loading...
Name
s13705-015-0057-5.pdf
Size
1.6 MB
Format
Adobe PDF