Alcohol fuels

HomeLearnFuel TypesAlcohol Fuels

Most road vehicles with spark-ignition engines use petrol, a light hydrocarbon fuel refined from crude oil. Alcohol fuels are low carbon liquid substitutes for, or blendstocks into, conventional petrol. Once they meet the relevant fuel quality standard, alcohol fuels are blended with conventional petrol and used in existing vehicles and refuelling infrastructure, subject to blend limits set by each fuel’s specification.

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Bioethanol Isobutanol Renewable ETBE

Bioethanol

Also known as

E10 / E85 (blend designations)
Anhydrous fuel ethanol
Ethyl alcohol
Hydrous ethanol (E100)

Bioethanol is an alcohol produced by fermenting sugars from crops such as sugarcane, corn, wheat and sorghum, or from cellulosic residues. It is blended into petrol as an oxygenate and octane booster, most commonly as E10 in Australia.

Key standards and certifications
Technical

Australian fuel quality regulations under the Fuel Quality Standards Act 2000

Australian Government

Fuel Quality Standards (Petrol) Determination 2024

Sets minimum quality requirements for petrol sold in Australia and permits up to 10% ethanol blending.

Fuel Quality Standards (Ethanol E85) Determination 2024

Sets fuel quality requirements for E85 (70-85% ethanol with 15-30% petrol balance).

Fuel Quality Standards (Ethanol E85) Information Standard 2019

Sets labelling requirements at point of sale for E85 fuel.

Fuel Quality Standards (Ethanol) Information Standard 2019

Sets labelling requirements at point of sale for E10 fuel.

EN 15376

Automotive fuels – Ethanol as a blending component for petrol – Requirements and test methods

European specification for the bioethanol blendstock used to make ethanol-petrol blends, applied alongside EN 228 for finished petrol.

ASTM D4806

Standard Specification for Denatured Fuel Ethanol for Blending with Gasolines for Use as Automotive Spark-Ignition Engine Fuel

US specification for denatured fuel ethanol blended with petrol at 1-15% by volume. The reference fuel ethanol standard in North America. Applies in the United States and many ASTM-aligned jurisdictions.

ASTM D5798

Standard Specification for Ethanol Fuel Blends for Flexible-Fuel Automotive Spark-Ignition Engines

US specification for high-ethanol blends (51-83% ethanol) used as fuel in flex-fuel vehicles. Companion standard to ASTM D4806.

EN 228

Automotive fuels – Unleaded petrol – Requirements and test methods

European petrol specification that permits up to 10% ethanol by volume (subject to an overall 3.7% oxygen content limit).

Certifications and schemes

International Sustainability and Carbon Certification (ISCC)

ISCC System GmbH

Voluntary, globally recognised certification covering biofuel sustainability, GHG emissions and chain of custody. ISCC EU compliance enables product sale into European markets under the Renewable Energy Directive II/III (RED II/III).

Bonsucro

Bonsucro Production Standard

Voluntary certification specific to sugarcane and its derivatives (including sugarcane-derived ethanol), covering environmental, social and economic sustainability.

Roundtable on Sustainable Biomaterials (RSB)

Global certification standard for sustainable biomaterials, biofuels and biomass production.

Multi-stakeholder voluntary standard covering sustainability of biofuel feedstocks, conversion and chain of custody.

Guarantee of Origin scheme

Australian Government (Clean Energy Regulator)

Voluntary Australian scheme that provides a transparent, publicly accessible record of the emissions associated with the production of key commodities. The scheme is being expanded to cover low carbon liquid fuels.

Production pathways

Standards and approvals
  • Fuel Quality Standards (Petrol) Determination 2024 (Australia)
  • Fuel Quality Standards (Ethanol E85) Determination 2024 (Australia)
  • ASTM D4806 (anhydrous fuel ethanol)
  • ASTM D5798 (E51-E83 blends for flex-fuel vehicles)
  • EN 15376 (ethanol blending component)
  • EN 228 (unleaded petrol up to E10)
Maximum blend
  • Up to 10% (E10) in standard petrol
  • Up to 85% (E85) in flex-fuel vehicles
  • 100% (E100) in dedicated ethanol vehicles
Main feedstocks
Sugar crops (sugarcane, sugar beet) and starch crops (corn, wheat, sorghum)

Bioethanol from sugar crops

Sugar cropcane, beet
→
Crushing and juice extraction
→
Sugar juice / molasses
→
Fermentationyeast
→
Distillation to fuel ethanol

This pathway also produces bagasse (often combusted on-site for power and heat) and stillage co-products.

Bioethanol from starch crops

Starch cropcorn, wheat
→
Milling + saccharification
→
Fermentable sugars
→
Fermentationyeast
→
Distillation to fuel ethanol

Co-products include distillers’ grains (DDGS), used as livestock feed

Standards and approvals
  • Fuel Quality Standards (Petrol) Determination 2024 (Australia)
  • Fuel Quality Standards (Ethanol E85) Determination 2024 (Australia)
  • ASTM D4806
  • ASTM D5798
  • EN 15376
  • EN 228
Maximum blend
  • Up to 10% (E10) in standard petrol
  • Up to 85% (E85) in flex-fuel vehicles
  • 100% (E100) in dedicated ethanol vehicles
Main feedstocks
Lignocellulosic biomass: agricultural residues (bagasse, straw, stover), forestry residues, energy grasses; municipal solid waste (organic fraction)

Cellulosic ethanol from lignocellulosic biomass

Lignocellulosic biomass
→
Pretreatment
→
Enzymatic hydrolysis
→
C5/C6 sugars
→
Fermentationyeast
→
Distillation to fuel ethanol

Lignin co-product is typically combusted on-site for process heat and power

Chemically identical to first-generation bioethanol once distilled – the difference is the feedstock and the upstream conversion steps

Isobutanol

Also known as

2-methylpropan-1-ol
Biobutanol (when biologically produced)
iBuOH
Isobutyl alcohol

Isobutanol is a four-carbon alcohol that substitutes for or extends conventional petrol. Compared with ethanol, isobutanol has higher energy density, lower water affinity and lower volatility, allowing higher petrol blend ratios without engine or infrastructure modification. Produced by fermentation using engineered organisms, isobutanol can serve the same blending role as ethanol while reducing the technical constraints on blend ratio.

Key standards and certifications
Technical

Australian fuel quality regulations under the Fuel Quality Standards Act 2000

Australian Government

Fuel Quality Standards (Petrol) Determination 2024

Permits oxygenates (including isobutanol) in petrol up to specified oxygen content limits. Isobutanol’s lower volatility makes it compatible with standard petrol limits at higher blend ratios than ethanol.

EN 228

Automotive fuels – Unleaded petrol – Requirements and test methods

European petrol specification permits isobutanol as an oxygenate up to 15% by volume, subject to an overall 3.7% oxygen content limit.

ASTM D7862

Standard Specification for Butanol for Blending with Gasoline for Use as Automotive Spark-Ignition Engine Fuel

US specification for n-butanol and isobutanol used as blending components in petrol up to 12.5% by volume. The reference butanol standard in North America.

Certifications and schemes

International Sustainability and Carbon Certification (ISCC)

ISCC System GmbH

Voluntary, globally recognised certification covering biofuel sustainability, GHG emissions and chain of custody.

Guarantee of Origin scheme

Australian Government (Clean Energy Regulator)

Voluntary Australian scheme that provides a transparent, publicly accessible record of the emissions associated with the production of key commodities. The scheme is being expanded to cover low carbon liquid fuels.

Roundtable on Sustainable Biomaterials (RSB)

Global certification standard for sustainable biomaterials, biofuels and biomass production.

Multi-stakeholder voluntary standard covering sustainability of biofuel feedstocks, conversion and chain of custody.

Production pathways

Standards and approvals
  • Fuel Quality Standards (Petrol) Determination 2024 (Australia)
  • ASTM D7862
  • EN 228 (subject to oxygen content limits)
Maximum blend
  • Up to 12.5% under ASTM D7862
  • Up to 15% under EN 228 oxygen content limits
Main feedstocks
Sugar and starch crops (sugarcane, sugar beet, corn, wheat); biomass-derived sugars

Isobutanol via fermentation of sugars

Sugar/starch feedstock
→
Pretreatment to fermentable sugars
→
Fermentationengineered organisms
→
Crude isobutanol
→
Separation + purification

Isobutanol’s higher energy density and lower water affinity than ethanol allow higher petrol blend ratios without infrastructure modification.

Renewable ethyl tert-butyl ether (ETBE)

Also known as

Bio-ETBE
Ethyl tertiary-butyl ether

Renewable ETBE is an oxygenated ether produced by reacting bioethanol with isobutylene. It serves as a high-octane oxygenate blendstock in petrol with better fuel-handling properties than ethanol, lower volatility, lower water affinity and easier storage. ETBE inherits its renewable carbon content from the bioethanol portion. Renewable ETBE is most widely used in European markets where it competes with bioethanol as a petrol oxygenate.

Key standards and certifications
Technical

Australian fuel quality regulations under the Fuel Quality Standards Act 2000

Australian Government

Fuel Quality Standards (Petrol) Determination 2024

Permits ethers (including ETBE) in petrol subject to overall oxygen content limits.

EN 228

Automotive fuels – Unleaded petrol – Requirements and test methods

European petrol specification permits ETBE up to 22% by volume, subject to an overall 3.7% oxygen content limit. The primary regulatory anchor for ETBE in petrol.

Certifications and schemes

International Sustainability and Carbon Certification (ISCC)

ISCC System GmbH

Voluntary, globally recognised certification covering biofuel sustainability, GHG emissions and chain of custody. ISCC EU compliance enables product sale into European markets under the Renewable Energy Directive II/III (RED II/III).

Guarantee of Origin scheme

Australian Government (Clean Energy Regulator)

Voluntary Australian scheme that provides a transparent, publicly accessible record of the emissions associated with the production of key commodities. The scheme is being expanded to cover low carbon liquid fuels.

Roundtable on Sustainable Biomaterials (RSB)

Global certification standard for sustainable biomaterials, biofuels and biomass production.

Multi-stakeholder voluntary standard covering sustainability of biofuel feedstocks, conversion and chain of custody.

Production pathways

Standards and approvals
  • Fuel Quality Standards (Petrol) Determination 2024 (Australia)
  • EN 228
Maximum blend
  • Up to 22% by volume in petrol under EN 228
  • Typical commercial blends 10-15%
Main feedstocks
Bioethanol (renewable component) reacted with isobutylene (typically fossil-derived; bio-isobutylene routes emerging)

Renewable ETBE from bioethanol and isobutylene

Bioethanol + isobutylene
→
Catalytic etherification
→
Distillation to ETBE

ETBE has higher energy density and lower volatility than ethanol, allowing easier blending into petrol.

Other drop-in renewable petrol pathways

These pathways are small-volume products globally, and none are currently produced at commercial scale in Australia.

The main drop-in renewable petrol pathways are:

  • Bio-naphtha from hydroprocessed esters and fatty acids (HEFA) refining. A petrol-range hydrocarbon co-produced when fats, oils and greases are processed into renewable diesel and sustainable aviation fuel (SAF).
  • Methanol-to-petrol (also called methanol-to-gasoline, MTG). A catalytic process that converts methanol into petrol-range hydrocarbons. The methanol input can be made from biomass, from natural gas, or from hydrogen combined with captured carbon dioxide (COâ‚‚).
  • Fischer-Tropsch (FT) synthesis. A chemical process that converts synthesis gas – a mixture of carbon monoxide and hydrogen (Hâ‚‚) – into liquid hydrocarbons. Petrol-range cuts are produced alongside diesel and jet fractions.
  • Power-to-liquid (PtL) petrol, or e-petrol. A liquid fuel made by combining hydrogen produced using renewable electricity with a carbon source such as captured carbon dioxide.
Keep exploring
Feedstock supply Fuel certification Sectors

Resources

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