What Is Biofuel?
- Car ownership
- How it works
FixMyCar explains what biofuel is and how it works.
Book a car repair nowEllie Dyer-Brown
Thursday July 25 2024
6 min read
The race is on to reduce global CO2 emissions, leading vehicle manufacturers and fuel suppliers to experiment with alternative fuel sources. Biofuel - a form of fuel made from living matter - is one of the outcomes of this experimentation.
This guide explores what biofuels are, how they work, and whether they’re likely to play a significant role in the future of transportation.
What is biofuel?
Biofuel is a liquid fuel made using renewable organic materials (biomass), including algae and plants. The two most common types are ethanol, a form of alcohol made from sugarcane and corn, and biodiesel, which is made from animal fats and vegetable oil. These alternative fuels represent the first generation of biofuel technology.
When burned in a combustion engine, biofuels produce less ozone, sulphur oxide and carbon monoxide. They still release some carbon dioxide into the atmosphere, but it is offset by the CO2 absorbed by the plants grown to make the fuel.
In the UK, suppliers of more than 450,000 litres of fuel per year are required by the Renewable Transport Fuel Obligation (RTFO) to sell a percentage of their fuel from sustainable and renewable sources.
How is biofuel made?
The process of preparing biomass for fuel production is called conversion.
Bioethanol
The most common conversion method is fermentation, which uses enzymes and yeast to break down sugar and starches into ethanol. The resulting liquid is called bioethanol because it is made from biological materials.
The other way of producing bioethanol involves extracting starch from wheat and maize, which can be used to make sugar.
Ethanol can only be used in car engines after the water has been removed - to achieve this, the liquid is distilled, and a final process of dehydration removes any remaining water.
Biodiesel
Biodiesel is made using a very different process called transesterification. It involves combining the fat or oil with a catalyst (such as sodium hydroxide) or alcohol (such as methanol) and heating the mixture, which breaks it down into fatty acid methyl esters (FAMEs) and glycerine.
You’ve probably got products that contain glycerin in your cupboards, such as soap, foods and skin products. However, it isn’t needed for biofuels, so it’s removed. The remaining liquid is biodiesel.
So, you might be wondering: why aren’t we all driving cars that run purely on biofuels if they are readily available? The answer is that neither bioethanol nor biodiesel contains as much energy per litre as conventional petrol or diesel, so you can’t swap one for the other and expect the same performance.
Instead, they are blended to create a hybrid fuel that decreases harmful emissions and improves combustion performance.
How does biofuel work?
Bioethanol is distilled, purified and blended with petrol to create a fuel that can be used in existing combustion engines. The two must be combined because bioethanol alone is about 30% less efficient than petrol, which would result in a drastic drop in fuel efficiency.
You can identify bioethanol fuels because they are labelled with an E in front of a number. E5 was the most common form of biofuel in the UK until 2021, containing up to 5% renewable ethanol. Today, E10 is more common, containing up to 10% renewable bioethanol.
Although using E10 fuel can slightly reduce fuel economy, the amount is so tiny that it is hardly noticeable. Under-inflated tyres or fitting a roof rack will have a more significant impact.
All new cars produced since 2011 are compatible with E10 fuel.
Biodiesel can be used in diesel engines as a sustainable alternative to traditional diesel, but - like bioethanol - it’s less efficient than petrol. There are quality and blend variations. Blended fuel is signalled by a B, followed by the percentage of biodiesel in the mixture.
Is biofuel renewable?
Biofuels must be produced using raw materials (called feedstocks) that are environmentally friendly and sustainable. Their production and use could continue indefinitely, making them a renewable fuel source.
Examples of biofuels
E5 - 95% petrol and 5% ethanol
E10 - 90% petrol and 10% ethanol
E85 - 85% ethanol and 15% petrol (used for flexible fuel vehicles)
B7 - 93% diesel and 7% biodiesel
What is biofuel used for?
Biofuel can be used for:
Transportation
Heat generation
Electricity generation
According to government figures, the UK biofuel industry has grown from almost nothing in 2005 to supplying over 220 million litres in 2023, including 43.1 million litres of biodiesel and 153.2 million litres of bioethanol.
Pros and cons of biofuel
Pros
Uses organic waste products that would have otherwise been thrown away
Reduces harmful emissions
Used cooking oil could be a substitute for diesel in some vehicles, but research is required beforehand to prevent damage
Cons
Using biofuel that is incompatible with your vehicle could cause severe damage
E10 is slightly less efficient than pure petrol
Growing plants for biofuel takes up land that could have been used for growing food
Growing and transporting plants for biofuel produces CO2 emissions
The future of biofuel
Bioenergy researchers are developing the next generation of advanced biofuels and products. Scientists might do this by:
Improving genes in plants to make them easier to break down for processing into fuel
Designing enzymes and microbes tailored to breaking down plant materials into sugars
Designing microbes that excel at converting these materials into chemicals used for fuel
Working with technicians and engineers to find processes that produce feedstock in cost-effective ways that minimise the use of other resources, such as water
All biofuels must use environmentally friendly and sustainable feedstocks.
Why is biofuel not more widely used?
This is an interesting question because, in some respects, biofuel is already widely used in blended fuels. When you fill-up with petrol, you’ll usually see E10 written on the pump, which means you’re using 10% bioethanol.
Interestingly, vehicles in countries like Sweden and Brazil run on 15% ethanol and 85% petrol, which the UK could start doing in the future. (However, at the time of writing, there are no official plans for such a change.)
Regardless of how widely fuel blends are used, some argue that the lack of investment in biofuels is because they only provide a stop-gap solution. The ban on new petrol and diesel cars will come into force in 2035, and electric vehicles are the most likely replacement.
In the medium term, biofuels remain a vital solution to rising emissions. However, their use is likely to decline as more drivers opt to go all-electric, especially with the emergence of rival alternative fuels, known as synthetic or e-fuels.
F1, which currently uses E10 fuel, plans to achieve Net Zero by 2030, and as part of this mission, the sport is developing a ‘drop-in’ 100% sustainable fuel that can be used by both F1 and conventional road cars from 2026. This new e-fuel will be lab-created and carbon-neutral.
Looking for affordable car repairs or maintenance? You're in the right place.
If you found this guide helpful, you might also like:
Written by Ellie
Ellie is FixMyCar's Content Writer. She has over three years of experience writing about cars and regularly collaborates with automotive experts to provide trustworthy advice for drivers that is easy understand. Her work has been featured in Yahoo! Finance, iNews, The Daily Express and The Sun. She has a BA in English literature and an MA in creative writing from Durham University. Outside of work, Ellie follows F1 and eagerly awaits Ferrari's next era of dominance in the sport. She drives a Suzuki Swift.