Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance
Sustainable solutions are needed to manage increased energy demand and waste generation. Renewable energy production from abundant sewage sludge (SS) and digestate (D) from biogas is feasible. Concerns about feedstock contamination (heavy metals, pharmaceuticals, antibiotics, and antibiotic-resistan...
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2020-06-01
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| Series: | Energies |
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| Online Access: | https://www.mdpi.com/1996-1073/13/12/3161 |
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| author | Kacper Świechowski Martyna Hnat Paweł Stępień Sylwia Stegenta-Dąbrowska Szymon Kugler Jacek A. Koziel Andrzej Białowiec |
| author_facet | Kacper Świechowski Martyna Hnat Paweł Stępień Sylwia Stegenta-Dąbrowska Szymon Kugler Jacek A. Koziel Andrzej Białowiec |
| author_sort | Kacper Świechowski |
| collection | DOAJ |
| description | Sustainable solutions are needed to manage increased energy demand and waste generation. Renewable energy production from abundant sewage sludge (SS) and digestate (D) from biogas is feasible. Concerns about feedstock contamination (heavy metals, pharmaceuticals, antibiotics, and antibiotic-resistant bacteria) in SS and D limits the use (e.g., agricultural) of these carbon-rich resources. Low temperature thermal conversion that results in carbonized solid fuel (CSF) has been proposed as sustainable waste utilization. The aim of the research was to investigate the feasibility of CSF production from SS and D via torrefaction. The CSF was produced at 200~300 °C (interval of 20 °C) for 20~60 min (interval 20 min). The torrefaction kinetics and CSF fuel properties were determined. Next, the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of SS and D torrefaction were used to build models of energy demand for torrefaction. Finally, the evaluation of the energy balance of CSF production from SS and D was completed. The results showed that torrefaction improved the D-derived CSF’s higher heating value (<i>HHV</i>) up to 11% (<i>p</i> < 0.05), whereas no significant <i>HHV</i> changes for SS were observed. The torrefied D had the highest <i>HHV</i> of 20 MJ∙kg<sup>−1</sup> under 300 °C and 30 min, (the curve fitted value from the measured time periods) compared to <i>HHV</i> = 18 MJ∙kg<sup>−1</sup> for unprocessed D. The torrefied SS had the highest <i>HHV</i> = 14.8 MJ∙kg<sup>−1</sup> under 200 °C and 20 min, compared to <i>HHV</i> 14.6 MJ∙kg<sup>−1</sup> for raw SS. An unwanted result of the torrefaction was an increase in ash content in CSF, up to 40% and 22% for SS and D, respectively. The developed model showed that the torrefaction of dry SS and D could be energetically self-sufficient. Generating CSF with the highest <i>HHV</i> requires raw feedstock containing ~15.4 and 45.9 MJ∙kg<sup>−1</sup> for SS and D, respectively (assuming that part of feedstock is a source of energy for the process). The results suggest that there is a potential to convert biogas D to CSF to provide renewable fuel for, e.g., plants currently fed/co-fed with municipal solid waste. |
| first_indexed | 2024-03-10T19:04:00Z |
| format | Article |
| id | doaj.art-39330e74ca3346528235673738e5db3b |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-10T19:04:00Z |
| publishDate | 2020-06-01 |
| publisher | MDPI AG |
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| series | Energies |
| spelling | doaj.art-39330e74ca3346528235673738e5db3b2023-11-20T04:12:51ZengMDPI AGEnergies1996-10732020-06-011312316110.3390/en13123161Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy BalanceKacper Świechowski0Martyna Hnat1Paweł Stępień2Sylwia Stegenta-Dąbrowska3Szymon Kugler4Jacek A. Koziel5Andrzej Białowiec6Faculty of Life Sciences and Technology, Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37/41 Chełmońskiego Str., 51-630 Wrocław, PolandFaculty of Life Sciences and Technology, Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37/41 Chełmońskiego Str., 51-630 Wrocław, PolandFaculty of Life Sciences and Technology, Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37/41 Chełmońskiego Str., 51-630 Wrocław, PolandFaculty of Life Sciences and Technology, Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37/41 Chełmońskiego Str., 51-630 Wrocław, PolandFaculty of Chemical Technology and Engineering, Polymer Institute, West Pomeranian University of Technology, 10 Pułaskiego Str., 70-322 Szczecin, PolandDepartment of Agricultural and Biosystems Engineering, Iowa State University, Ames, IA 50011, USAFaculty of Life Sciences and Technology, Institute of Agricultural Engineering, Wrocław University of Environmental and Life Sciences, 37/41 Chełmońskiego Str., 51-630 Wrocław, PolandSustainable solutions are needed to manage increased energy demand and waste generation. Renewable energy production from abundant sewage sludge (SS) and digestate (D) from biogas is feasible. Concerns about feedstock contamination (heavy metals, pharmaceuticals, antibiotics, and antibiotic-resistant bacteria) in SS and D limits the use (e.g., agricultural) of these carbon-rich resources. Low temperature thermal conversion that results in carbonized solid fuel (CSF) has been proposed as sustainable waste utilization. The aim of the research was to investigate the feasibility of CSF production from SS and D via torrefaction. The CSF was produced at 200~300 °C (interval of 20 °C) for 20~60 min (interval 20 min). The torrefaction kinetics and CSF fuel properties were determined. Next, the differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) of SS and D torrefaction were used to build models of energy demand for torrefaction. Finally, the evaluation of the energy balance of CSF production from SS and D was completed. The results showed that torrefaction improved the D-derived CSF’s higher heating value (<i>HHV</i>) up to 11% (<i>p</i> < 0.05), whereas no significant <i>HHV</i> changes for SS were observed. The torrefied D had the highest <i>HHV</i> of 20 MJ∙kg<sup>−1</sup> under 300 °C and 30 min, (the curve fitted value from the measured time periods) compared to <i>HHV</i> = 18 MJ∙kg<sup>−1</sup> for unprocessed D. The torrefied SS had the highest <i>HHV</i> = 14.8 MJ∙kg<sup>−1</sup> under 200 °C and 20 min, compared to <i>HHV</i> 14.6 MJ∙kg<sup>−1</sup> for raw SS. An unwanted result of the torrefaction was an increase in ash content in CSF, up to 40% and 22% for SS and D, respectively. The developed model showed that the torrefaction of dry SS and D could be energetically self-sufficient. Generating CSF with the highest <i>HHV</i> requires raw feedstock containing ~15.4 and 45.9 MJ∙kg<sup>−1</sup> for SS and D, respectively (assuming that part of feedstock is a source of energy for the process). The results suggest that there is a potential to convert biogas D to CSF to provide renewable fuel for, e.g., plants currently fed/co-fed with municipal solid waste.https://www.mdpi.com/1996-1073/13/12/3161renewable energysewage sludgebiogas digestatewaste to energywaste to carboncircular economy |
| spellingShingle | Kacper Świechowski Martyna Hnat Paweł Stępień Sylwia Stegenta-Dąbrowska Szymon Kugler Jacek A. Koziel Andrzej Białowiec Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance Energies renewable energy sewage sludge biogas digestate waste to energy waste to carbon circular economy |
| title | Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance |
| title_full | Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance |
| title_fullStr | Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance |
| title_full_unstemmed | Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance |
| title_short | Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance |
| title_sort | waste to energy solid fuel production from biogas plant digestate and sewage sludge by torrefaction process kinetics fuel properties and energy balance |
| topic | renewable energy sewage sludge biogas digestate waste to energy waste to carbon circular economy |
| url | https://www.mdpi.com/1996-1073/13/12/3161 |
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