Agricultural and Biosystems Engineering Publications
Campus Units
Agricultural and Biosystems Engineering, Civil, Construction and Environmental Engineering, Food Science and Human Nutrition, Toxicology
Document Type
Article
Publication Version
Published Version
Publication Date
6-18-2020
Journal or Book Title
Energies
Volume
13
Issue
12
First Page
3161
Research Focus Area(s)
Biological and Process Engineering and Technology
DOI
10.3390/en13123161
Abstract
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 (HHV) up to 11% (p < 0.05), whereas no significant HHV changes for SS were observed. The torrefied D had the highest HHV of 20 MJ∙kg-1 under 300 °C and 30 min, (the curve fitted value from the measured time periods) compared to HHV = 18 MJ∙kg−1 for unprocessed D. The torrefied SS had the highest HHV = 14.8 MJ∙kg−1 under 200 °C and 20 min, compared to HHV 14.6 MJ∙kg−1 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 HHV requires raw feedstock containing ~15.4 and 45.9 MJ∙kg−1 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.
Access
Open
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Copyright Owner
The Author(s)
Copyright Date
2020
Language
en
File Format
application/pdf
Recommended Citation
Świechowski, Kacper; Hnat, Martyna; Stępień, Paweł; Stegenta-Dąbrowska, Sylwia; Kugler, Szymon; Koziel, Jacek A.; and Białowiec, Andrzej, "Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by Torrefaction-Process Kinetics, Fuel Properties, and Energy Balance" (2020). Agricultural and Biosystems Engineering Publications. 1137.
https://lib.dr.iastate.edu/abe_eng_pubs/1137
Included in
Bioresource and Agricultural Engineering Commons, Energy Systems Commons, Environmental Engineering Commons, Sustainability Commons
Comments
This article is published as Świechowski, Kacper, Martyna Hnat, Paweł Stępień, Sylwia Stegenta-Dąbrowska, Szymon Kugler, Jacek A. Koziel, and Andrzej Białowiec. "Waste to Energy: Solid Fuel Production from Biogas Plant Digestate and Sewage Sludge by TorrefactionProcess Kinetics, Fuel Properties, and Energy Balance." 13, no. 12 Energies (2020): 3161. DOI: 10.3390/en13123161. Posted with permission.