Work

Hydrothermal Liquefaction for Biofuel Synthesis: Assessment of VFA (Volatile Fatty Acid) and FAME (Fatty Acid Methyl Ester) Profiles from Spent Coffee Grounds

Year: 2025

Type: article

Abstract: Spent coffee grounds (SCG) are an underutilized biomass resource with high potential for renewable energy and bioproducts synthesis. This study applies hydrothermal liquefaction to transform SCG into high-quality biofuels and value-added biochemicals. Five experiments were conducted over a temperature range of 300 °C to 380 °C, highlighting significant temperature-dependent shifts in product composition. Notably, phenolic compounds peaked at 1,180.1 mg/L at 300 °C before declining sharply, while chemical oxygen demand (COD) dropped to a minimum of 13,949.8 mg/L at 350 °C—a temperature that also maximized hydrochar yield (26%) and achieved a high heating value of 32.9 MJ/kg. Plasma chromatographic analyses showed the dynamic behavior of volatile fatty acids (VFAs) and fatty acid methyl esters (FAMEs); maximum levels of acetic (540.7 mg/L), formic (67.8 mg/L), and propionic acids (155.6 mg/L) were recorded at 300 °C, whereas FAMEs such as methyl butyrate, methyl hexanoate, methyl undecanoate, and methyl palmitate increased markedly at higher temperatures due to intensified carboxylation reactions. These results denote the potential of hydrothermal liquefaction to valorize SCG for the production of biomolecules, expanding the conventional sustainable biofuel production pathways.

Source: Energies

DOI: 10.3390/en18082094

Authors: Dimitrios Liakos, Georgia Altiparmaki, Simos Malamis, Stergios Vakalis

Institutions: University of the Aegean, National Technical University of Athens

Language: English

Topic: Thermochemical Biomass Conversion Processes

Subfield: Biomedical Engineering

Field: Engineering

Domain: Physical Sciences

SDGs: Responsible consumption and production, Affordable and clean energy, Climate action

Open Access status: gold

Estimated APC paid: $3,137