The rapid expansion of biodiesel production has created an equally significant challenge: the accumulation of crude glycerol. Although glycerol is generated naturally during biodiesel manufacturing, it is far from pure. The by-product commonly contains methanol, soaps, catalyst residues, salts, water, and free fatty acids, making it unsuitable for direct industrial use and reducing its commercial value.
Rather than treating crude glycerol as industrial waste, scientists increasingly view it as a valuable renewable feedstock. One of its most attractive products is 1,2-propanediol, also known as propylene glycol, a colorless, low-toxicity compound used in food, beverages, pharmaceuticals, cosmetics, and personal care products. It functions as a solvent, humectant, stabilizer, flavor carrier, and texture modifier and is recognized for approved food applications in several international regulatory systems.
Unlike many conventional production methods that depend on expensive metal catalysts and high-pressure hydrogen, the Indonesian researchers explored an alternative laboratory route using a sequence of chemical reactions. The process involved three main stages: producing biodiesel from palm oil through transesterification, purifying the resulting crude glycerol, and converting the purified glycerol into 1,2-propanediol through intermediate chemical transformations. The identity of each product was confirmed using Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography–Mass Spectrometry (GC-MS), and Proton Nuclear Magnetic Resonance (^1H NMR).
The experimental results demonstrated that the conversion pathway was technically successful.
Key findings include:
- Biodiesel production generated 10.38% crude glycerol relative to the palm oil feedstock.
- Sulfuric acid purification recovered glycerol with 89.80% yield and 95.80% chromatographic purity.
- The intermediate compound, identified as prop-2-en-1-ol, achieved 75.13% yield with 83.66% purity.
- The final product, 1,2-propanediol, reached 77.73% isolated yield and 96.82% GC-area purity.
- Process simulations indicated that additional technical modifications, including dual distillation and optimization of hydrogen-to-glycerol ratios, could further improve purity to approximately 99%.
Spectroscopic analyses supported each stage of the chemical transformation. FTIR measurements showed the expected appearance and disappearance of characteristic functional groups during purification and conversion. GC-MS confirmed the dominant compounds in each reaction stage, while ^1H NMR spectra matched the molecular structures expected for purified glycerol, the intermediate unsaturated alcohol, and the final 1,2-propanediol product. Together, these analytical techniques provided consistent evidence that the laboratory process successfully produced a 1,2-propanediol-rich fraction.
The researchers also emphasized that high chromatographic purity alone does not guarantee that the product is ready for commercial food applications. Additional testing remains necessary before the material can meet food-grade specifications. Recommended analyses include quantitative GC or HPLC using authentic standards, Karl Fischer water determination, residual solvent measurements, inorganic residue analysis, and targeted testing for ethylene glycol and diethylene glycol impurities.
The study also places its findings within the broader context of sustainable manufacturing. Because glycerol is an unavoidable by-product of biodiesel production, upgrading it into a valuable chemical improves resource efficiency and reduces industrial waste. Instead of disposing of crude glycerol or using it as a low-value fuel, manufacturers may eventually convert it into ingredients used by the food, pharmaceutical, cosmetic, and chemical industries, increasing the economic value of renewable energy production.
However, the authors caution that sustainability should not be evaluated solely by reaction yields. Their laboratory process still requires sulfuric acid, formic acid, potassium hydroxide, organic solvents, repeated extraction steps, and heating temperatures up to 260°C. These factors influence energy consumption, waste generation, production costs, and environmental performance. As a result, the researchers recommend future life-cycle assessment, techno-economic evaluation, and food-grade safety analysis before considering industrial-scale implementation.
As Iffana Dani Maulida of Universitas Terbuka and Jumina of Universitas Gadjah Mada explain through their findings, the analytical evidence consistently supports the successful production of a 1,2-propanediol-rich product from biodiesel-derived glycerol. At the same time, they stress that additional quantitative purity testing, impurity profiling, and regulatory qualification are essential before the material can be classified as food-grade.
If validated at larger scales, the proposed conversion pathway could contribute to cleaner biodiesel production, strengthen Indonesia's bio-based chemical industry, and create new economic opportunities by transforming renewable energy waste into high-value industrial materials.
Author Profile
Iffana Dani Maulida, is a lecturer in the Department of Food Technology, Faculty of Science and Technology, Universitas Terbuka, Indonesia. Her expertise includes food technology, food chemistry, biomass utilization, and food additive development.
Jumina, is Professor of Chemistry at the Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada (UGM), Indonesia. His research focuses on organic chemistry, organic synthesis, catalysis, and biomass-based chemical development.
Source
Maulida, I. D., & Jumina. (2026). Preparation of 1,2-Propanediol as Food Additives from Glycerol as Biodiesel By-product. Indonesian Journal of Interdisciplinary Research in Science and Technology (MARCOPOLO), Vol. 4, No. 3, pp. 167–186.
DOI: 10.55927/marcopolo.v4i3.30.
URL: https://journalmarcopolo.my.id/index.php/marcopolo
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