Petrol vs Ethanol Emissions: Is Ethanol Fuel Environmentally Friendly?

As per India Today, The Union government is reportedly targeting 30% ethanol blending with petrol by 2030 to reduce dependence on imported oil further while addressing environmental concerns.

With the world facing climate change and air pollution, the transportation sector, being one of the principal sources of greenhouse gas (GHG) emissions, is also facing scrutiny.

Fossil fuels such as petrol have been the traditional energy source for cars for a very long time, but their environmental cost has given rise to alternatives such as ethanol and hydrogen.

Ethanol, which is a biofuel derived from resources such as corn or sugarcane, is commonly presented as a more environmentally friendly choice owing to its renewable origin.

Hydrogen, incorporated into fuel cell vehicles (FCEVs), is also promised zero tailpipe emissions. But are these alternatives so kind to the environment after all?

This article compares the emission of petrol, ethanol, and hydrogen-based on life cycle assessments, case studies, and statistics to analyze their environmental ramifications, particularly if the green image of ethanol holds.

Emissions from Petrol Fuel

Petrol, which is a crude oil-derived complex hydrocarbon mixture, is used to fuel the majority of internal combustion engines. It produces numerous pollutants that have profound environmental and public health consequences:

• Carbon Dioxide (CO2): The major greenhouse gas responsible for global warming. One litre of petrol produces about 2,329 g of CO2 upon combustion, and an average passenger car produces around 4.6 metric tons of CO2 per year (US EPA).

• Nitrogen Oxides (NOx): Produced by high-temperature combustion, NOx is a source of smog and acid rain, impairing air quality and ecosystems.

• Carbon Monoxide: A poisonous gas from combustion that is dangerous to human health even at low concentrations.

• Hydrocarbons (HC): Volatile unburned fuel that vents to the air and adds to smog formation.

• Particulate Matter (PM): Tiny particles that can penetrate the lungs, causing respiratory issues.

New petrol cars sold within the European Union emitted 106.4 g CO2/km on average in 2023, and within the UK, 143 g CO2/km (European Environment Agency EEA; RAC Foundation).

These emissions are responsible for driving climate change and air pollution, especially in cities, and petrol is thus an important environmental factor.

Emissions from Ethanol Fuel

Ethanol is a biofuel made from renewable biomass such as corn, sugarcane, or cellulosic material.

It is commonly mixed with petrol (e.g., E10, E85) to lower emissions and dependence on fossil fuels.

Its emission footprint differs from petrol in several important respects:

• Carbon Dioxide (CO2): CO2 is emitted from the combustion of ethanol but has reduced life cycle emissions since the growth of feedstock crops captures CO2. For instance:

  • Bioethanol from sugar beet produces 1,504 g CO2/litre on combustion but only 901 g CO2/litre of life cycle GHG emissions.

  • Bioethanol from wheat produces 1,504 g CO2/litre on combustion but only 168 g CO2/litre on a life cycle basis (Forest Research).

• Secondary Emissions: Ethanol-blended gasoline lowers CO, HC, and certain air toxics from petrol but can also emit more acetaldehyde, which is a suspected carcinogen (Alternative Fuels Data Center).

• Life Cycle Analysis (LCA): Research indicates that corn-based ethanol cuts greenhouse gas (GHG) emissions 40-50% compared to petrol, and cellulosic ethanol can reduce emissions by 88-108%, which varies based on feedstocks (Alternative Fuels Data Center).

Comparison Chart: Petrol vs Ethanol Carbon Emissions

The following table, taken from Forest Research, demonstrates the lower life cycle emissions of ethanol, especially using wheat.

Is Ethanol Environmentally Friendly?

The environmental footprint of ethanol is an area of controversy where both benefits and issues are present.

Note:

• Lower GHG emissions: The life cycle emissions for ethanol are much lower than for petrol, driven down by 40-50% from corn-based ethanol and by up to 108% from cellulosic ethanol (Alternative Fuels Data Center).

• Renewable Source: Unlike nonrenewable petroleum, ethanol is created from renewable biomass, which facilitates long-term sustainability.

• Energy security: Ethanol helps to lessen dependency on foreign oil that countries such as India aspire to gain independence from (Iowa Farm Bureau).

Challenges:

• Land-use Changes: Massive ethanol production may result in deforestation or the destruction of natural ecosystems to use for agriculture, releasing sequestered carbon and negatively impacting biodiversity (Yale e360).

• Water use: Corn ethanol production is water-guzzling and may stress local water supplies.

• Food vs. Fuel Debate: Using food crops like corn for fuel can increase food prices, raising ethical concerns, especially in developing nations.

• Nitrous Oxide (N2O) Emissions: Fertilizer application for ethanol crop production also tends to enhance N2O, an effective GHG that cancels out some gains.

Case studies

• United States Renewable Fuel Standard (RFS): The United States mandated the blending of ethanol to curb transportation emissions. There is evidence that corn-based ethanol can cut 40-50% of GHG emissions, but land use effects are still an area of debate (Alternative Fuels Data Ascertain).

• Brazilian Sugarcane Ethanol Programme: Brazil’s use of sugarcane ethanol has lowered the use of fossil fuel and reduced life cycle emissions by 50-70% compared to petrol. However, the production of more sugarcane land has resulted in the destruction of forests in a few regions (Iowa Farm Bureau).

Ethanol may be included within a sustainable energy policy, yet its eco-friendliness will depend upon sustainable production methods, including utilizing non-food crops or enhancing farm efficiency.

Hydrogen as Alterhnative Fuel

FCEVs produce electricity from hydrogen gas, and the only tailpipe pollutants are warm air and water vapour. They are an encouraging substitute for petrol and ethanol.

• Tailpipe emissions: FCEVs give off zero CO2, NOx, CO, HC, or PM and are thus especially useful for enhancing city air quality (Alternative Fuels Data Center).

• Life cycle emissions: The environmental footprint relies on hydrogen production:

  • Green hydrogen: Made from renewable energy (e.g., wind, sunlight) through electrolysis, its life-cycle emissions are as low as 2-3 g CO2e/MJ (The Conversation).

  • Grey hydrogen: Manufactured from natural gas without capturing its carbon, it may emit 100 g CO2e/MJ, which is equivalent to or even worse than petrol.

  • Blue Hydrogen: Utilizes natural gas and carbon capture, lowering emissions but not ideal compared to green hydrogen.

Comparison Chart: Life Cycle GHG Emissions per MJ

This table brings together data from Forest Research and The Conversation.

Challenges: Insufficient fueling infrastructure, high production cost, and energy consumption to produce (notably green hydrogen) are hindering adoption (Carwow).

Potential: There is potential for FCEVs to become a cornerstone of low-carbon transportation, especially for heavy-duty vehicles or areas that have ample renewable energy, if green hydrogen production and infrastructure advance.

Ethanol provides substantial life cycle reductions in greenhouse gas emissions compared to petrol, while corn ethanol delivers 40-50% reductions and cellulosic ethanol up to 88-108%.  This is due to the renewable nature of ethanol’s feedstocks and advancements in production processes. Source

It is not entirely environmentally friendly, though, due to land use changes, water usage, and impacts on the cost of food.

Hydrogen FCEVs, due to their zero tailpipe emissions and very low life cycle emissions potential using green hydrogen, are an advanced future choice, but existing grey hydrogen dependence and limited infrastructure hold their deployment back.

For India, where energy security and air quality are both urgent issues, ethanol blending of type E10 or E20 can represent an interlude strategy, making use of agricultural resources and enhancing sustainability.

Hydrogen, while not yet viable, also holds long-term promise, particularly if supplemented by India’s expanding renewable energy base.

A harmonized strategy—mixing the use of biofuels, hydrogen, electric and hybrid vehicles, and better motor vehicle efficiency—will be essential to minimizing the environmental impact of transportation.