Dual-Waste Valorization: Sustainable Biodiesel Production from High-FFA Sludge Palm Oil Using Silica-Rich Water Treatment Sludge as A Low-Cost Catalyst Support

M. Anshari; Meta Rivani; Muhammad Erlangga Habibi Nasution; Muhammad Ansori Nasution; Tubagus Rayyan Fitra Sinuhaji

doi:10.29017/scog.v49i2.2051

Authors

M. Anshari Indonesian Oil Palm Research Institute
Meta Rivani Indonesian Oil Palm Research Institute
Muhammad Erlangga Habibi Nasution Indonesian Oil Palm Research Institute
Muhammad Ansori Nasution Indonesian Oil Palm Research Institute
Tubagus Rayyan Fitra Sinuhaji Universitas Diponegoro

DOI:

https://doi.org/10.29017/scog.v49i2.2051

Keywords:

sludge palm oil, dual-waste valorization, water treatment sludge, heterogeneous catalyst, biodiesel

Abstract

To address feedstock costs and environmental sustainability, this study employed a dual-waste valorization strategy by converting high-free fatty acid (FFA) sludge palm oil (SPO) into biodiesel using silica-rich water treatment sludge from PDAM as a low-cost support for a heterogeneous K₂O/SiO₂ catalyst. Due to the high initial acidity of SPO, a two-step process was used: acid esterification to reduce FFA levels below 2%, followed by alkaline transesterification. Optimization of the reaction parameters identified the ideal conditions as 6% catalyst loading, a 15:1 methanol-to-oil molar ratio, and a 2-hour reaction time at 63°C. Under these conditions, the process achieved a biodiesel yield of 70.43% with a high methyl ester purity of 98.01%. The produced biodiesel met the SNI 7182:2015 quality standards for density and acid number. Although the catalyst demonstrated stability over two consecutive cycles, its activity declined in the third cycle due to active-site leaching. This work confirms the viability of integrating industrial and municipal waste streams for sustainable and cost-effective bioenergy production.

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