Sludge from waste-cooking-oil pretreatment for biodiesel is organic-rich but low value. Pyrolysis separated it into liquid, gas and carbon-rich solid. Light, middle and heavy liquid cuts had higher heating values of 44.3-44.6 MJ/kg, while gas reached a 53.6 MJ/Nm3 Wobbe Index suitable for thermal applications. Higher temperature shifted yield from liquid to gas. Biochar retained energy and carbon-storage potential, but salinity and alkali constrain land use.
Key findings
- Liquid cuts reached 44.3-44.6 MJ/kg; gas Wobbe Index was 53.6 MJ/Nm3; higher temperature reduced liquid and increased gas; biochar retained energy and carbon but had salinity and alkali constraints.
Why this matters globally
Biodiesel plants could reduce disposal and recover energy from an overlooked residue. Recycling product gas into the process may reduce external fuel and improve circularity.
Thai researcher contribution
Nathawat Unsomsri, Songkran Wiriyasart, Pachara Koedthong, Natcha Yongying, Paranee Sriromreun and Sommas Kaewluan form the Srinakharinwirot University team driving the experimental circular-resource work.
Limitations to consider
Heating value does not establish oxygen content, acidity, viscosity, contaminants or emissions. Detailed mass yields, energy balance, replicates and pilot operation are absent from the abstract. Sludge biochar needs contaminant testing, and carbon storage must account for process energy.