# One-step Hydrothermal Liquefaction and Catalytic Upgrading of Wastewater-Grown Microalgae for Potential Sustainable Aviation Fuel Precursors

## TL;DR

This study explores converting wastewater-grown microalgae into sustainable aviation fuel using a one-step process that produces high-quality bio-oil.

## Contribution

A one-step hydrothermal liquefaction and catalytic upgrading method is proposed for producing sustainable aviation fuel precursors from wastewater-grown microalgae.

## Key findings

- A bio-oil yield of 23.07% was achieved at 320°C with a 10% NiMo/Al2O3 catalyst.
- The highest heating value of 41.77 MJ kg–1 was obtained with a 120-minute reaction time.
- A 30-minute process is recommended for energy efficiency with minimal impact on results.

## Abstract

In the context of aviation decarbonization goals, this
study investigated
the conversion of wastewater-grown microalgae into sustainable aviation
fuel (SAF) precursor via one-step hydrothermal liquefaction (HTL)
and upgrading. The highest bio-oil yield achieved was 23.07% (dry
basis), at 320 °C for 30 min with 10% NiMo/Al2O3 catalyst. The highest heating value, 41.77 MJ kg–1, was obtained under the same temperature and catalyst concentration,
but with a longer reaction time (120 min). Bio-oil yield was significantly
influenced by temperature, while the catalyst played a key role in
sulfur reduction. The response surface analysis identified an intersection
region, around 324 °C with 15% NiMo/Al2O3 catalyst, that offers a favorable balance between high yield and
low sulfur content. Since reaction time had no significant impact
on the results, a 30 min process is recommended to improve energy
efficiency. Bio-oil presented a predominance of aromatic hydrocarbons,
with smaller fractions of alkanes and cycloalkanes, compounds that
are desirable for SAF. These results highlight HTL as a promising
pathway for wastewater-grown microalgae valorization. However, further
refining and comprehensive technical, economic, and environmental
assessments are needed to advance the use of this bio-oil as SAF precursor.