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. 2024 Mar 15;9(12):14530-14538.
doi: 10.1021/acsomega.4c00455. eCollection 2024 Mar 26.

Nitrogen Minimization in Hydrothermal Liquefaction Biocrude from Sewage Sludge with Green Extraction Solvents

Muhammad Usman  1 , Shuo Cheng  1 , Sasipa Boonyubol  1 , Jeffrey S Cross  1
Affiliations

Nitrogen Minimization in Hydrothermal Liquefaction Biocrude from Sewage Sludge with Green Extraction Solvents

Muhammad Usman et al. ACS Omega. .

Abstract

This study explored the effectiveness of hydrothermal liquefaction (HTL) in converting sewage sludge (SS) into high-quality biocrude. It scrutinized the influence of various solvents, including conventional choices like dichloromethane (DCM) and hexane, alongside environmentally friendly alternatives, such as ethyl butyrate (EB) and ethyl acetate (EA). HTL experiments, conducted at 350 °C for 60 min in a 20 mL batch reactor, include solvent-based biocrude extraction. Notably, EB showed the highest extraction yield (50.1 wt %), the lowest nitrogen distribution (5.4% with 0.32 wt %), and a remarkable 74% energy recovery (ER), setting a noteworthy benchmark in nitrogen reduction. GCMS analysis reveals EB-derived biocrude's superiority in having the least heteroatoms and nitrogenous compounds compared to hexane, EA, and DCM. Solid residues from hexane, EB, and EA displayed the highest nitrogen distribution range (62-68%), hinting at potential applications in further processes. These findings significantly inform solvent selection for efficient and sustainable waste-to-energy conversion. While promising, the study emphasizes the need to explore solvent-solute interactions further to optimize biocrude quality, highlighting the pivotal role of solvent choice in advancing clean, cost-effective waste-to-energy technologies.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
HTL of SS experimental flow and product separation.
Figure 2
Figure 2
Product yield of the SS HTL experiment at 350 °C.
Figure 3
Figure 3
Distribution of chemical compounds in extracted biocrudes identified by GCMS.
Figure 4
Figure 4
Possible reaction pathways of these chemical compounds in extracted biocrudes.
Figure 5
Figure 5
Nitrogen distribution in HTL products of SS.
Figure 6
Figure 6
Energy recovery in HTL products of SS.
See this image and copyright information in PMC

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