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May 12, 2026Energy Conversion and Management X0 citationsOpen Access

Evaluation of the performance and emissions of diesel engines powered by minimally refined palm oil produced using calcined limestone

BYB. G. Yudanto FPF. R. Panjaitan HAH. Ambarita

Key Points

This research aims to assess the performance and emissions of diesel engines powered by minimally refined palm oil (MRPO), produced using a low-energy refining method.
Engine tests conducted over 1050 hours on a 37 kW diesel generator using MRPO and B40 fuel for comparison.
MRPO is produced through dry fractionation and treatment with a limestone-derived alkaline precursor, with total process energy significantly lower than traditional methods.
Benchmarked against B40 to evaluate emissions and performance metrics such as torque, power, and fuel consumption.
MRPO shows comparable torque with a ≤0.84% penalty and 5.74% lower power compared to B40.
Exhaust opacity reduced by 3.8-fold (3.5% vs. 13.3%), with similar NOx and CO emissions.
Production cost of MRPO estimated at USD 1.4/kg and process energy 30-fold lower than conventional biodiesel methods.

Abstract

• Novel low-energy palm oil refining using calcined limestone catalyst. • 1050-hour engine test shows MRPO performance matches standard biodiesel. • Production cost is ∼70% lower than conventional biodiesel methods. • MRPO meets national fuel standards with comparable emissions to B40. • Enables decentralized, affordable biofuel for off-grid electrification. Decarbonizing off-grid power generation in palm-oil-producing nations requires affordable biofuels. Conventional palm biodiesel production via transesterification or hydrotreating adds high processing costs (USD 4. 77–12. 53/kg) and energy burden (20–25 MJ/L). This study presents a novel minimally refined palm oil (MRPO) produced through a low-intensity route: dry fractionation of crude palm olein, treatment with a limestone-derived CaO/Ca (OH) 2 alkaline precursor (5 wt%, 80–95°C, 5 min), centrifugation, five-stage warm-water washing, and vacuum drying, bypassing transesterification entirely. The precursor, synthesized by calcination of natural limestone at 800°C and hydration–dehydration, exhibited strong basicity (H_= 15. 0–18. 4) and reduced acid value by 96%, phosphorus by 99%, and kinematic viscosity by 29% relative to crude palm oil. Total process energy was only 0. 66 MJ/L. The resulting MRPO met Indonesian stationary biofuel specifications and was benchmarked against B40 (40% FAME/60% diesel) in a 1, 050 h diesel-generator endurance test on a 37 kW engine. MRPO showed comparable torque (≤0. 84% penalty), 5. 74% lower power, and 7. 93% higher specific fuel consumption, attributed to higher viscosity and lower heating value. Exhaust opacity was reduced by 3. 8-fold (3. 5% vs. 13. 3%), while NOx and CO were similar. Used oil analyses (viscosity, TBN, TAN, wear metals) remained stable throughout the test, and post-test inspection revealed no critical wear or deposits. With estimated production cost of USD 1. 4/kg and a 30-fold lower process energy than transesterification, MRPO offers a technically viable, low-emission, and economically accessible stationary fuel.

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