Integration of Hydrothermal Carbonisation with Anaerobic Digestion; Opportunities for Valorisation of Digestate
Open accessAbstract
Hydrothermal carbonisation (HTC) has been identified as a potential route for digestate enhancement producing a solid hydrochar and a process water rich in organic carbon. This study compares the treatment of four dissimilar digestates from anaerobic digestion (AD) of agricultural residue (AGR); sewage sludge (SS); residual municipal solid waste (MSW), and vegetable, garden, and fruit waste (VGF). HTC experiments were performed at 150, 200 and 250 °C for 1 h using 10%, 20%, and 30% solid loadings of a fixed water mass. The effect of temperature and solid loading to the properties of biocoal and biochemical methane potential (BMP) of process waters are investigated. Results show that the behaviour of digestate during HTC is feedstock dependent and the hydrochar produced is a poor-quality solid fuel. The AGR digestate produced the greatest higher heating value (HHV) of 24 MJ/kg, however its biocoal properties are poor due to slagging and fouling propensities. The SS digestate process water produced the highest amount of biogas at 200 °C and 30% solid loading. This study concludes that solely treating digestate via HTC enhances biogas production and that hydrochar be investigated for its use as a soil amender.
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Treating sewage sludges and digestate using HTC can overpass its limitation in energy compared to other thermochemical processes, and hydrochar produced is more stable.
“However, recent studies showed that treating sewage sludges and digestate using HTC can overpass its limitation in energy compared to other thermochemical processes. The hydrochar that can be produced from this process was seen to be more stable (Parmar and Ross 2019).”
From Mechanisms and adsorption capacities of biochar for the removal of organic and inorganic pollutants from industrial wastewater (2021) · cites this paper as Parmar and Ross 2019
The Introduction describes HTC as a way to treat high-moisture feedstocks and notes the drying and energy-balance barriers of pyrolysis. It does not establish that HTC overcomes an energy limitation relative to other thermochemical processes; it also says energy densification is not always observed for sewage sludge. Neither the Introduction nor the Conclusions establishes that the resulting hydrochar is more stable, and the Conclusions caution that digestate hydrochar is a poor solid fuel. (LLM, conf=0.82)
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References 72 · Cited by 139
- Authors
- Parmar, K. R., & Ross, A. B.
- Affiliations
- University of Leeds (GB)
- Corresponding author
- Ross, Andrew B.
- ORCID
- Parmar, Kiran R.
- Venue
- Energies
- Publisher
- MDPI AG
- Published
- 2019-04-26
- Volume
- 12
- Issue
- 9
- Pages
- 1586
- ISSN
- 1996-1073 (ISSN-L)
- OpenAlex
- W2940976090
- Cited by
- 139
- References
- 72
- Citations by year
- 2026: 8 · 2025: 17 · 2024: 25 · 2023: 20 · 2022: 26 · 2021: 27 · 2020: 15 · 2019: 1
- FWCI
- 6.08
- Type
- journal article
- Language
- en
- Open access
- gold
- dx.doi.org
- Licence
- Locations
- Energies (publishedVersion, cc-by)
- White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
- RePEc: Research Papers in Economics (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- Funders
- University of Leeds (EP/L014912/1)
- Topics
- Physical Sciences › Engineering › Biomedical Engineering › Thermochemical Biomass Conversion Processes
- Physical Sciences › Engineering › Building and Construction › Anaerobic Digestion and Biogas Production
- Physical Sciences › Chemical Engineering › Catalysis › Catalysts for Methane Reforming
- Keywords
- hydrothermal carbonization, anaerobic digestion, hydrochar, bio-coal, process water, sewage sludge, agricultural residues, municipal solid waste, vegetable waste, biochemical methane potential, biogas production, solid loading, temperature effects, higher heating value, soil amendment
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