Bio-Crude Production Improvement during Hydrothermal Liquefaction of Biopulp by Simultaneous Application of Alkali Catalysts and Aqueous Phase Recirculation

Komeil Kohansal,Kamaldeep Sharma,Thomas Helmer Pedersen,Lasse Aistrup Rosendahl,Saqib Sohail Toor,Joscha Zimmermann,Eliana Lozano Sanchez

doi:10.3390/en14154492

Komeil Kohansal, Kamaldeep Sharma + Show 5 more

Open Access

https://doi.org/10.3390/en14154492

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Journal: Energies	Publication Date: Jul 25, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: Aalborg University, Karlsruhe Institute of Technology

Abstract

This study focuses on the valorization of the organic fraction of municipal solid waste (biopulp) by hydrothermal liquefaction. Thereby, homogeneous alkali catalysts (KOH, NaOH, K2CO3, and Na2CO3) and a residual aqueous phase recirculation methodology were mutually employed to enhance the bio-crude yield and energy efficiency of a sub-critical hydrothermal conversion (350 °C, 15–20 Mpa, 15 min). Interestingly, single recirculation of the concentrated aqueous phase positively increased the bio-crude yield in all cases, while the higher heating value (HHV) of the bio-crudes slightly dropped. Compared to the non-catalytic experiment, K2CO3 and Na2CO3 effectively increased the bio-crude yield by 14 and 7.3%, respectively. However, KOH and NaOH showed a negative variation in the bio-crude yield. The highest bio-crude yield (37.5 wt.%) and energy recovery (ER) (59.4%) were achieved when K2CO3 and concentrated aqueous phase recirculation were simultaneously applied to the process. The inorganics distribution results obtained by ICP reveal the tendency of the alkali elements to settle into the aqueous phase, which, if recovered, can potentially boost the circularity of the HTL process. Therefore, wise selection of the alkali catalyst along with aqueous phase recirculation assists hydrothermal liquefaction in green biofuel production and environmentally friendly valorization of biopulp.

Highlights

This type of residue has been viewed as the bothersome part of municipal solid waste (MSW) that can hamper the usage of recycling technologies, but, at the same time, it represents a sustainable source of carbon exploitable for liquid fuels and nutrients for agriculture
Far, composting has been employed to treat the organic fraction of MSW; low energy recovery (ER) rates as well as the increased risk of microplastic contamination are the major drawbacks of this technology [7]
Containing more than 19.2% of crude fats along with 49.3% of carbohydrates, biopulp can potentially be considered as a promising biomass in hydrothermal liquefaction (HTL)

Summary

Introduction

Around 28–58% of the produced MSW by most countries consists of organic waste [5]. Far, this type of residue has been viewed as the bothersome part of MSW that can hamper the usage of recycling technologies, but, at the same time, it represents a sustainable source of carbon exploitable for liquid fuels and nutrients for agriculture. Far, composting has been employed to treat the organic fraction of MSW; low energy recovery (ER) rates as well as the increased risk of microplastic contamination are the major drawbacks of this technology [7]

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Results

Conclusion