The truth about demon fuels

Diesel, wood-burning stoves and now gas have all hit the headlines as super-polluters. But what’s wrong with these sources of energy? Are they really as damaging as the experts say? And what are the alternatives?

Diesel, wood-burning stoves and now gas have all hit the headlines as super-polluters. But what’s wrong with these sources of energy? Are they really as damaging as the experts say? And what are the alternatives?

What is classed as a demon fuel?

With its friendly blue flame, natural gas is synonymous with cosiness. But its reign may well be coming to an end, in moves that see it put in the same ‘demon fuels’ category as diesel and the wood used in log burners.

Chancellor Philip Hammond pronounced what could be the death knell of gas in his Spring Statement, when he declared a ban on using fossil fuels to heat new-build homes, to come into force by 2025.

Diesel too, is under fire from all sides, the latest blow being London’s new Ultra Low Emission Zone. And wood burners have incurred the ire of clean air campaigners including London Mayor Sadiq Khan, who has called for tighter curbs on them.

But are these fuels really so bad? And what will we do if we can’t use them? We take a look...

“To meet our climate targets, we need to reduce our dependence on burning natural gas to heat our homes,” said Philp Hammond in his Spring Statement. It followed a report by the Committee on Climate Change, which recommends that from 2025 at the latest, no new homes should be connected to the gas grid.

Weaning the UK off gas won’t be simple

It’s easily our favourite fuel, powering around 85% of the UK’s domestic central heating, with an average household burning through around 12,000 kWh of the stuff every year. Around half of us use it for cooking too. And it’s not just heating and eating – around half of the UK’s electricity is supplied by natural gas.

There are exceptions: some rural homes in mainland Britain aren’t connected to the gas grid and rely on oil and liquid petroleum gas (LPG) to stay warm. And in Northern Ireland, which has a less developed gas transmission network, around two thirds of homes have oil central heating. But, on the whole, Britain’s households run on natural gas.

The trouble with gas

So what’s the problem with gas anyway? Well, natural gas is a fossil fuel. It’s formed from plants and animals that lived hundreds of millions of years ago and have rotted away under the sea bed and layers of rock, releasing the mix of methane and other gases that make up natural gas. Burning gas produces heat, but it also gives off the carbon dioxide that’s leading to global warming.
And that’s not the only issue.
The UK isn’t self-sufficient in gas; we depend on other countries – including Norway, the Netherlands, Qatar and Russia – for more than half of what we use. Over fifty per cent of our gas is imported, and, with the decline of offshore gas production, the fear is that this figure will go up. This has led to forays into another way of getting our favourite fuel: fracking.

What is fracking?

Fracking involves extracting shale gas from rock by injecting water and chemicals at high pressure. It’s hugely controversial, having been linked with earthquakes and water contamination. Despite government insistence that fracking can be done safely and with minimal environmental risks, the Cuadrilla fracking operation in Lancashire has attracted repeated protests, and fracking was suspended there between 2011 and 2018 because of earth tremors. Not so cosy.

LPG has a lower carbon footprint than oil

Rapeseed is used as a source of biofuel

Heat pumps are a greener solution

Gas hobs in new homes may be banned

Gas alternatives

So how could we stay warm without gas? Existing alternatives available for homes that are off grid are oil-fired central heating and LPG. UK domestic central heating systems tend to use 28sec oil, also known as kerosene. But heating oil can face similar or worse charges about its carbon footprint as gas. LPG fares slightly better as it has a lower carbon and lower overall environmental impact than heating oil. These alternatives can also be more expensive than gas too. So what are the greener alternatives to replace gas for heating?
Some smaller suppliers are producing a bio-heating oil made from vegetable oils, but this is not widely available in the UK at the moment. It could be a useful alternative if based on waste vegetable oils. However, some biofuels have been criticised for being made by growing crops that go up in smoke rather than being used to feed people.

Heat pumps

The main idea that’s been mooted for future homes is the use of heat pumps. These draw heat from the ground, or work by taking in air from outside a building to heat up liquid, which is then sent to radiators or underfloor heating. Just be warned you might have to have larger radiators and higher-standard insulation to achieve the same room temperature.

Electric or induction hobs 

But what about cooking? No connection to the gas grid would mean no gas hobs. The alternatives are electric or induction hobs – but the latter can only work with induction-compatible pots and pans. However, the Spring Statement didn’t go as far as saying there would be no gas grid connection at all, so gas hobs may be around for a while yet.

Journey to a new world

The problem with all this, says Sofia Hutson, head of energy at Compare the Market, is that it hasn’t been completely thought through.

“There’s been talk about moving to a world where electricity is generated, stored and distributed at a local level. With solar, wind farms and other forms of electrical generation you could possibly see the distribution mechanism changing relatively quickly. But gas is a different beast,” she says.
“There’s a lot of complexity, difficulty and cost in moving away from the current infrastructure to something new.”

However, there are already signs that consumers are falling out of love with fossil fuels. The number of ‘green’ tariffs has risen from what Ofgem describes as ‘negligible’ in 2016, to 56 in June 2018. And Sofia Hutson confirms that consumers are choosing them.

“Green tariffs are on the increase both in terms of prevalence and people switching to them,” she says. “They are often not the cheapest, so customers are making a choice based of factors other than just price.”

Demonising diesel 

Diesel suffers from the same problems as gas in that it’s a fossil fuel that produces emissions. But – although it might be hard to believe now – today’s demonised diesel was once seen as a pollution solution.
It all started in 1997 when nations that signed up to the Kyoto Agreement pledged to cut their CO2 emissions. Diesel produces less CO2 than petrol, so it was seen as a quick, easy answer to a problem. Taxes on diesels were cut and car buyers responded accordingly with millions of people in the UK buying new diesel cars.
Then it all went wrong.

What happened to diesel?

It turns out that CO2 emissions aren’t the only ones to worry about. In around 2012, Nitrogen oxide (NOx) and particulate matter (PM) started to emerge as a significant health problem. These tiny particulates are linked with everything from respiratory disease to heart attacks to cancer. And they come from diesel exhausts.
It’s been pretty much downhill all the way for diesel ever since. In 2015, the Volkswagen scandal hit the headlines when it was revealed that the manufacturer was fiddling vehicle emissions tests.
Meanwhile, governments in Europe tried to limit the health risks of diesel vehicles by banning them from city centres and raising taxes on them. In the UK, measures have included raising Vehicle Excise Duty, introducing higher parking charges for some diesels, and, from April 2019, the introduction of an Ultra Low Emission Zone (ULEZ) in London.

If vehicles don’t meet minimum emissions standards when driving in the ULEZ, they’ll have to pay a £12.50 daily charge on top of the Congestion Charge. This could cost over £3,000 a year for someone who uses their car every weekday.

How the ULEZ works

Petrol cars registered after 2005 will probably be compliant with the standards, whereas only diesel cars registered after September 2015 are likely to meet them. And it doesn’t stop here – other cities are expected to follow suit with their own zones.
Not surprisingly, all this has led to a sharp decline in the popularity of diesel cars, with registrations falling sharply in early 2019.
The U-turn over diesel has sparked anger among some motorists who feel they have been punished for owning a type of vehicle they were once encouraged to buy. The most extreme manifestation of this has been in France, where the gilets jaunes protests were originally sparked by a rise in diesel tax. But the fact is that, in the UK at least, the road for both diesel and petrol looks to be running out.

The future for diesel

Diesel cars are now generally accepted to be much cleaner, and many car experts say it’s still worth buying a diesel if you do a lot of mileage, as diesel is more fuel efficient than petrol.

But in the longer term, the days of both diesel and petrol look to be numbered. The government has pledged to phase out the sale of new cars of both types by 2040. So with petrol also about to join the ranks of demon fuels, electric vehicles are now being touted as a clean transport solution. However, some experts are warning of the high carbon footprint created by the lithium ion batteries used in electric cars, as well as dependence on fossil fuels for electricity generation. So whether a different set of problems will emerge from electric vehicles is yet to be seen.

Wood-burning woes

Fossil fuels aren’t the only energy baddies these days. The problem of particulates rears its head again when it comes to wood-burning stoves and open fires.

Wood is a sustainable, carbon-neutral fuel. Plus, it’s relatively cheap and extremely cosy. So it’s not surprising that so many of us have invested in a wood-burning stove – according to The Green Age, there are around 1.5 million of them being used in the UK.

As well as thinking you’re doing right by the environment, as a wood-burning stove owner you might even experience getting back to nature by using wood from your garden as fuel.

Unfortunately though, wood burners and open fires are in the frame as polluters – and ‘found’ wood is one of the worst offenders. The problem is that when wood – especially wet wood – burns, it produces tiny, sooty particles that can exacerbate respiratory and heart problems.

The stove of the future

So does the particulate problem mean the end for wood burners? Unlike gas and diesel, no one is talking about getting rid of them entirely. But the government has announced outlawing the sale of all but the least polluting stoves by 2022. They will also give local authorities more powers to take action in areas of high pollution – something that London Mayor Sadiq Khan has been calling for.

Khan meanwhile, has praised the stove industry itself for developing eco-design stoves and ‘ready to burn wood’. This has less moisture and emits less pollution than wet or ‘unseasoned’ wood, of the type you might find in your garden.

But like the owners of old diesel cars, the fact a new model of wood burning stove is available may be cold comfort for people who’ve already bought something they thought was environmentally friendly.

Moving targets

The saviour fuel of today may, of course, turn out to be the demon fuel of tomorrow. It’s not just diesel – biofuels, for example, were once touted as the answer to transport pollution, but pitfalls – namely the energy, resources and land needed to produce them outweighing their environmental benefits – soon became apparent. 
And while things need to change, the question is how exactly this will be done.

Sofia Hutson

Head of energy at Compare the Market

“We all have to look to the future and say things cannot stay the way they are. The planet is not going to sustain the current level of carbon fuel usage in powering homes." 
“But the alternatives at the moment are in their infancy in terms of development, and they’re going to be costly."
“Is it industry that bears that cost in addition to maintaining the existing infrastructure while we move to a new world? Is it government? Is it the players in those spaces? Or ultimately does that cost get passed on to the consumer in the form of either new kit in their homes or higher bills?”

Fuel facts


  • Gas gets to Britain from offshore gas fields, pipelines from Europe and in liquid form, carried by tankers.
  • Natural gas doesn’t smell – the odour is added so leaks can be detected.
  • Gas is owned by different suppliers, but distribution isn’t affected by who owns it – so if you switch supplier, your gas won’t be interrupted.


  • Diesel comes from crude oil. The UK’s six oil refineries supply most of our petroleum products, including diesel.
  • 30 million tonnes of diesel and other fuels are carried around the country via an extensive network of pipes.
  • In a petrol engine, fuel is ignited with spark plugs. In a diesel engine, it’s ignited with air.


  • Wood burners are popular in London and the South East.
  • Wood needs to be dried before burning – Defra recommends dry wood should have 20% moisture or less.