Bioethanol: Characteristics
Why a third less energy still makes a valuable fuel
What this tab covers The physical and chemical properties that set its grade, price and uses, with the commercial grades and the standards that define them.Fuel ethanol is sold to tight water, acidity and purity limits because water causes phase separation in petrol blends. Energy content is two-thirds of petrol per litre, but its high octane lets refiners use cheaper base petrol.
Properties that matter commercially
| Property | Value / specification | Why it matters | Source |
|---|---|---|---|
| Ethanol content (anhydrous, for blending) | at least 99.5% by volume (IS 15464, indicative); at least 98.7% m/m alcohol (EN 15376, indicative) | water above about 0.3-0.5% causes phase separation in blends | IS 15464; EN 15376 (indicative) |
| Energy content | about 26.8 MJ/kg (21.1 MJ/litre) lower heating value, against about 32 MJ/litre for petrol (indicative) | E20 cuts fuel economy by a few per cent | indicative |
| Octane | RON about 108 (indicative) | lets refiners make lower-octane base petrol | indicative |
| Denaturant | fuel ethanol is denatured with petrol, 1.96-5% in the US (ASTM D4806, indicative) | keeps it out of the excise-taxed beverage market | ASTM D4806 (indicative) |
Commercial grades
- Anhydrous fuel ethanol (blending)
- Hydrous ethanol (Brazil E100, about 95% ethanol)
- Extra neutral alcohol (potable)
- Rectified spirit and denatured industrial ethanol
- Pharma (IP/USP) grade