What Is Crude Glycerin? Characteristics, Production, and Uses
- Crude glycerin (raw glycerin) is a co-product of biodiesel transesterification and fat splitting with 80–88% glycerol, still containing salts, methanol, water, and other impurities.[1]
- Every 100 kg of biodiesel yields about 10 kg of crude glycerin, making supply very large in biodiesel-producing countries.[2]
- The product still contains inorganic salts, ash, and matter organic non-glycerol (MONG), so it is not directly suitable for food, pharmaceutical, or cosmetic use.[1]
- Vacuum distillation purification can raise glycerol content above 99.5%; refining residue is called glycerin pitch.[1]
- Uses include livestock feed as an energy source, boiler fuel, and feedstock for refining pure glycerol.[2]
Crude glycerin is unrefined glycerol produced as a co-product of the biodiesel and palm-based oleochemical industries. Its variable glycerol content requires purification before use in high-value products.
Table of contents
What Is Crude Glycerin?
Crude glycerin or raw glycerin is unrefined glycerol produced as a co-product of transesterification of vegetable oils into biodiesel and fat splitting in the oleochemical industry. Glycerol content ranges from 80–88%, depending on feedstock and production process.[1][2]
The product still contains impurities such as inorganic salts, methanol, water, ash, residual catalyst, and matter organic non-glycerol (MONG). For this reason crude glycerin is not directly suitable for food, pharmaceutical, or cosmetic industries before purification.[1]
The main difference from refined glycerin lies in glycerol content and purity. Refined glycerin has a minimum glycerol content of 99.5% and meets pharmaceutical standards, whereas crude glycerin still requires stepwise purification.[1]
Characteristics and Composition
Crude glycerin composition varies widely depending on feedstock source and production process. Raw glycerin from biodiesel typically contains 80–88% glycerol, salts, water, methanol, and MONG.[1][2]
| Component | Content | Source |
|---|---|---|
| Glycerol | 80–88% | Biodiesel and oleochemicals |
| Inorganic salts (NaCl) | 15–30% of residue | Glycerin pitch |
| Methanol | Process residue | Transesterification |
| Water | Process residue | Transesterification |
| Ash | Process residue | Catalyst and salts |
| Matter organic non-glycerol (MONG) | Process residue | Fatty acids and esters |
Production
Crude glycerin is produced by transesterification of vegetable oils with methanol using an alkali catalyst. This reaction yields biodiesel and glycerol in roughly a 9:1 ratio, so every 100 kg of biodiesel produces about 10 kg of crude glycerin.[2]
In the oleochemical industry, glycerin is also produced from triglyceride splitting (fat splitting) and saponification. Crude glycerin from these sources is then concentrated in a multi-effect evaporator to 80–88%.[1]
Crude glycerin purification can be done by adding phosphoric acid to neutralize catalyst and soap, followed by vacuum distillation. Research at IPB showed glycerol content could be raised from 47% to 83% with phosphoric acid, then reach 94.19% with vacuum distillation at 90–95 °C and 0.51 bar pressure.[3]
Applications
Crude glycerin is used as an energy source in livestock feed. Glycerol can be converted to glucose in the ruminant liver, so the product can potentially replace corn in beef cattle rations.[2]
In broiler chickens, vegetable glycerin can be mixed up to 15% without adverse effects, while in Nellore cattle the safe level reaches 30% of dietary dry matter.[2][4]
Crude glycerin is also used as boiler fuel and for power generation at biodiesel plants, and is added at 2–4% in pellet feed to increase pellet hardness and reduce dust. Purification residue in the form of glycerin pitch can be used in liquid soap formulations.[1][5]
Summary
Crude glycerin is raw glycerol at 80–88% content from biodiesel transesterification and fat splitting. It still contains salts, methanol, and other impurities, and is used for livestock feed, fuel, and as feedstock for refining pure glycerol.
References
- Warta PPKS (2025). Production and Utilization of Glycerin Pitch from Palm Oil-Based Oleochemical Industry. https://warta.iopri.org/index.php/Warta/article/download/236/125
- PMC/NIH. Glycerol use in dairy diets: A systemic review. https://pmc.ncbi.nlm.nih.gov/articles/PMC6739259/
- Bogor Agricultural University. Improvement of Glycerol Purification Process from Biodiesel Industry By-Products Using Vacuum Distillation. https://repository.ipb.ac.id/handle/123456789/74915
- PMC/NIH. Effects of Increasing Glycerin Levels in Broiler Chickens. https://pmc.ncbi.nlm.nih.gov/articles/PMC11205917/
- DaShu. Crude Glycerin 80% CG — specification and applications. https://www.cntreechem.com/crude-glycerin-80-cg/