The days of running cars on just petrol or diesel are numbered, as alternative fuels increasingly play their part in reducing carbon emissions.
Electric is the most well-known, but it’s not the only ‘green’ fuel being proposed and tested by manufacturers. We take look at the most important ones.
Electrified vehicles/electric cars – either as pure battery electric vehicles (BEVs) or plug-in hybrid electric vehicles (PHEVs) – are what are widely considered to be the future of alternatively fuelled transport.
BEVs use only the electrical energy stored in batteries to power a motor (or, in some instances more than one motor) that drives the wheels.
The batteries need to be topped with electricity from either a domestic or workplace charger, or a public one by the roadside or at a service station.
Plug-in hybrids also have batteries and electric motors, but the battery pack is smaller than in a BEV, so the distance they can travel on electric power is limited (usually around 30 miles).
As a result, they also have traditional engines for longer journeys.
In essence, PHEVs are a stepping stone between our reliance on combustion-engined cars and the change to full BEVs.
It’s highly likely that we will all be adopting electric cars over the next 30 years or so, with PHEVs easing us into our electric future.
Hydrogen Fuel Cells
It’s early days, but vehicles with hydrogen fuel cells are a strong possibility for future transport.
Hydrogen vehicles have fuel tanks that are filled with compressed hydrogen, which combines with air in a hydrogen fuel cell inside the car to create the electricity to power a motor.
All they emit is water, which just drips harmlessly onto the road.
There is a cost, however, of manufacturing the hydrogen itself, and it's currently unknown how ‘green’ that process will become.
Buyers can already buy hydrogen cars, in the form of the Toyota Mirai and Hyundai Nexo, but they’re pricey (between £65,000 and £70,000) and refuelling is a bit of a challenge.
There are just a handful of filling stations in the UK, most around London and the south-east, so it’s not a practical solution for most British drivers at the moment.
However, despite fuel costs per mile currently being slightly higher than petrol or diesel cars, the price of hydrogen fuel will come down as it’s produced in higher volumes, while fuel costs will also be offset by savings elsewhere, such as lower car tax.
LPG & CNG – Liquid Petroleum Gas & Compressed Natural Gas
Liquid petroleum gas (LPG) and compressed natural gas (CNG) have both been available for a number of years, but with the increasing urgency to reduce CO2 emissions, they are options that might become more attractive.
LPG (also known as Autogas) is a mix of propane and butane, with its use reducing CO2 exhaust emissions by around 15%, compared to petrol.
Around the world, it is the third most popular automotive fuel, but it’s not really made many inroads among British drivers.
CNG is compressed methane and many vehicles using it have a bi-fuel capability, so owners can use petrol or diesel and CNG.
This might make it attractive to drivers who aren’t ready for electricity or hydrogen.
One way in which these fuels could become more popular is for the government to offer tax breaks and other incentives in the future.
Biofuels are renewable fuels that can be mixed with petrol or diesel to create a lower-cost method of reducing CO2 emissions from vehicles.
Biodiesel is a blend of diesel and vegetable oil: it is in common use and can often be used without having to modify vehicles.
However, some manufacturer warranties don’t cover equipment damaged by certain blends of biofuel, so it's important for owners to check before switching.
Availability is also limited in the UK, so you’ll need to do your research before you go bio.
Yes, air. It's a technology that is still in its early days, but car engines that use compressed air are in development.
Compressed air is stored in a tank at high pressure, and rather than driving engine pistons with an ignited fuel-air mixture, compressed air cars use the expansion of compressed air. It’s a bit like how steam powers steam engine.
Compressed air has many advantages, including no tailpipe emissions, but some of the existing research shows that these types of vehicles are also less efficient than electric vehicles (although compressed air-electric hybrids could be a possibility).
Range anxiety is a fear of running out of electricity while driving.
It's a barrier to many car buyers going electric, but larger-capacity batteries are on their way, along with a raft of new electric car models.
At the same time, more high-speed public chargers (we’re starting to see them at filling stations, for example) will mean that within a few years, BEVs will be a more practical option, as well as being cheaper to run than petrol and diesel cars.