Running your car on waste vegetable oil

Last updated Monday 21 July 2008

A recipe for low-emission motoring?

Some diesel engines will run on waste cooking oil if it's brewed into biodiesel or blended with old fashioned 'fossil' diesel. If you convert your engine you can even use it neat. However you cut it, recycled oil will slash emissions from driving and can make a tasty saving against soaring pump prices.

Running your car on the same oil that fries your fish is a major CO2 saver and could be 'cheap as chips' too (especially if its free from the local greasy spoon). Cars running on cooking oil - used or otherwise - get similar fuel economy to diesels and 20-30% better than ordinary petrol.

In practice there isn't nearly enough of the stuff to fuel Britain's six million diesel cars, but if you have a pre-2000 low-pressure diesel engine, waste oil could be a golden opportunity for you and the climate - unlike the majority of 'primary' biofuels. In fact, the government's Better Regulation Commission is satisfied that waste cooking oil "makes economic and environmental sense."

And fiddling around with your engine isn't a must. An expanding network of filling stations sell biodiesel brewed from recycled oil which can be added to some unconverted engines. So can our waste veggie oil help us to stop cooking the climate?

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Photo: Running your car on waste vegetable oil

Saves up to 2,400kg of CO2 a year

61 Bloomers are doing this

CO2 reduction 4 out of 5

Cheapness 1 out of 5

Popularity 2 out of 5

Cost 500-1000

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It's Not Easy Being Green: biodiesel

Dick Strawbridge and Phill Tufnell discuss the savings associated with brewing your own biodiesel

In this article:

How will it make a difference?

Pub Fact

  • The catering industry in the UK produces about 50-90 million litres of waste cooking oil each year
  • Rudolf Diesel's very first engine was powered by peanut oil in 1900
  • Ireland discards more than 10,000 tonnes of waste vegetable oil every year
  • As much as 25% of waste cooking oil collected in the UK is being exported, mainly to Germany and France, according to the Better Regulation Commission
  • Recent reports suggest that there are about 35 companies making waste cooking oil biodiesel commercially in the UK

The average diesel car produces nearly three tonnes of CO2 a year. Switch to waste biodiesel (processed waste veggie oil) and you can expect to cut your driving emissions by about 85% , according to the Department for Transport. Convert your engine to run on pure waste cooking oil alone and your emissions will be dangerously close to zero. Of course, waste veggie oil produces CO2 but no more than the CO2 that the plant originally took out of the air through photosynthesis. Read the full report (Carbon and Sustainability Reporting Within the Renewable Transport Fuel Obligation, 2008).

A knock-on effect is that the oil you use would otherwise have gone down the drain or into landfill - where it leaks methane, a greenhouse gas. Over half of the 100,000 sewer blockages cleared each year by Thames Water result from fat - much of it poured down sinks. (For other ways to dispose of cooking oil, see 'How do I do it?')

In order to make the biggest carbon savings you need to convert your engine to run on pure, unprocessed veggie oil, which costs money up front (typically 500-1,000). Nevertheless, the savings can offset the conversion costs in a few months. After that, you're in profit on the deal.

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What's the debate?

"Is waste veggie oil 'carbon neutral'?"

Waste vegetable oil has already been used once, so boffins give it a size-zero carbon footprint. In fact, Swiss research published in 2007 found that the only transport biofuel that consistently performs better than petrol in environmental terms is waste cooking oil. That said, waste veggie oil still emits CO2 when it is combusted in your engine - but only as much as it absorbed while it was growing in a field. In addition, a burgeoning demand for waste vegetable oil could potentially spur further growth in the biofuel industry down the line. It's already fueling 'cooking oil wars' amongst biodiesel makers in London, according to the Telegraph. Read our article on the perils of 'primary' biofuels.

"If it's such a good idea why aren't we all doing it?"

There's simply not enough cooking oil in the UK to take over from diesel entirely according to the government's Better Regulation Commission. Current waste oil supplies could only feasibly power around one-350th of the UK's cars. In fact, the Energy Systems Research Unit estimates that the UK can only produce enough biodiesel from waste veggie oil to displace less than 0.6% of conventional diesel.

"Is running a car on pure vegetable oil legal? Doesn't the government levy tax on fuel?"

It's all perfectly above board, and there's no tax to pay unless you use more than 2,500 litres a year (enough to take you about 20,000 miles). Hang on to your receipts in case you're ever asked to prove you haven't exceeded the limit.

Beyond that point you'll need to establish the amount of duty payable per litre, a complex business dependent on whether its chemical consistency qualifies it for a biofuel reduction (call the HM Revenue and Customs' National Advice Service on 0845 010 9000 for details). You may be able to source your oil from a collective that will do these calculations for you.

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What's stopping me?

"I have a petrol car, not a diesel one."

Fair enough - only diesel cars can use vegetable oil. The alternative biofuel is ethanol based E85, but it's not nearly as eco-friendly. Yet.

"My local dealership says I can kiss my warranty goodbye."

It's very unlikely a manufacturer's warranty will be valid once you've converted a new car to veggie oil. And there are some other things to bear in mind too:

  • It's not advisable to put pure vegetable oil in modern high-pressure diesels as it may wreck the engine and land you with a repair bill running into several thousand pounds
  • You need to replace the fuel filter more often, but the new filter only costs around 10

"I don't want to convert my car to run on pure veggie oil. Is there an alternative?"

Yes. If the waste vegetable oil has been processed into biodiesel, then you can probably run your diesel car on it without conversion. (Generally speaking, cars built from 1994 onwards are probably ok - but it's worth checking with your car manufacturer). You can get waste vegetable biodiesel at some small biodiesel filling stations - or make it yourself from waste cooking oil.

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How do I do it?

If you have a diesel car, you may be able to run your car on pure waste vegetable oil:

  • Check with your car manufacturer whether your car can run on pure veggie oil - or is suitable for conversion to vegetable power
  • Inform your insurance company and car manufacturer of impending conversions
  • Check with your local greasy spoon whether you can collect their waste cooking oil - but make sure to buy a filter before you use the oil
  • For financial simplicity, search online for duty-paid, filtered veg oil suppliers
  • If you're the adventurous type, buy a DIY kit to convert your car to run on 100% veggie power
  • Vegetable oil freezes in the cold unlike agricultural biofuel - so consider mixing with traditional biodiesel or diesel in winter

If you can't run your car on pure waste veggie oil, don't despair:

  • An alternative is waste vegetable oil that has been processed into biodiesel. Look for your nearest biodiesel filling station and remember to check that their fuel is made from waste veggie oil
  • All station diesel now contains from 2.5-5% biodiesel - so adding another 5% of home-brew biodiesel risks breaking an unmodified engine and losing the warranty
  • Check that the processed waste biodiesel conforms to the EN 14214 standard
  • If you don't mind a spot of DIY, you can take a course in how to make waste biodiesel without blowing your house up: the Low Impact Living Initiative and the Centre for Alternative Technology
  • You can even teach yourself how to make waste biodiesel: there are plenty of online guides, including Gas 2.0, Journey To Forever and Schnews. And you can read a BBC article on how to make the stuff

If it all sounds a bit daunting, there are still more productive ways to dispose of your old vegetable oil than in the bin or down the sink:

  • Donate it to a recycling scheme so others can run their cars on it: see Reuze
  • Put small amounts in your compost bin, mixing it with cardboard or paper
  • If you're fond of our feathered friends, mix up any vegetable oil leftovers with seeds, nuts and raisins to make bird patties: Breathing Places
  • Find out what other opportunities you're wasting. Read our articles on recycling and low-carbon shopping

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Che Guava, Keighley 2009-03-04

Running VW caravelle on waste chip oil now for over 12 months manufactured in Keighley by Robin Fuels no problems.

Flower representing the 'Running your car on waste vegetable oil' action

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Glossary terms used on this page
Biodiesel is fuel generated from vegetable oil that can be used pure or blended with regular diesel (diesel produced by refining crude oil) in conventional, unmodified diesel engines. It is not the same as waste vegetable oil, otherwise known as 'unwashed biodiesel', which requires engine modification.
CO2, or carbon dioxide, is made up of the elements carbon and oxygen. It exists quite naturally in our atmosphere, as part of the carbon cycle. Everyday processes in the plant and animal world both add CO2 to the atmosphere and take it out. However, because it is a greenhouse gas - meaning it affects the temperature of the earth - the exact level of CO2 is important. Burning fossil fuels releases CO2 into the atmosphere, hence the anxiety that extensive use of these fuels is causing climate change.
Carbon neutral
A business or a process is described as carbon neutral if it doesn't add to the net amount of CO2 in the atmosphere. This can be achieved either by emitting no CO2 to begin with - by using only renewable energy, say - or by 'offsetting' emissions (a controversial issue) which means compensating for emissions by another action which might reduce atmospheric CO2, such as planting trees. In practice, it is impossible for a person to live in an entirely carbon neutral way because even if you cut out energy consumption derived from fossil fuels, most products and services people rely on will have embodied emissions.
Greenhouse gases
Greenhouse gases raise the earth's temperature through the greenhouse effect. There are six main examples. As well as carbon dioxide, they include: water vapour, methane, nitrous oxide, ozone and CFCs (which include sulphur hexafluoride, HFCs, and PFCs). Of these, carbon dioxide, methane, nitrous oxide, sulphur hexafluoride, HFCs, and PFCs are controlled under the Kyoto Protocol to limit their concentration in the atmosphere. The heat warming capacity of each gas is measured by its 'global warming potential': how much heat it traps depends on its chemical make-up and how long it stays in the atmosphere.
Methane is a hydrocarbon, the main component of natural gas and among the six greenhouse gases to be curbed under the Kyoto protocol. As a greenhouse gas it is estimated to have a warming effect about 25 times as great as CO2. (Compared to CO2 its effects are greater but last for a shorter period). As a fuel, it is used in electricity generation and in the form of compressed natural gas it can be used as vehicle fuel. Methane is produced during the decomposition of many materials in landfill, while about 16% of methane emissions are caused by livestock's digestive processes. navigation


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