Active transport is much better for the environment than relying on vehicles. But how carbon intensive are bicycles?

Important: click on each link below to find out more 

Your choice of transport really matters to both your pocket and planet.

Recently we discovered that many electric vehicles driven in Guernsey produce around 65% less carbon emissions across their entire lifecycle compared to petrol and diesel vehicles. These figures take into account the various stages of a lifecycle including:

  • battery production
  • diesel-generated electricity from the Vale power station
  • final vehicle and battery disposal

But many people choose to ride bicycles over a car, with an understanding that a conventional bike is naturally less carbon intensive than an electric bike.

Is this correct? We’ve summarised some interesting information from a book written by Mike Berners-Lee to start the conversation.

Electric Vehicles in Guernsey study source

Click the links below to find out more about what’s going on and what you can do. 

All bikes are far better for the environment than cars, but will still contain embodied CO² emissions due to manufacture and distribution

Are electric bikes more carbon friendly than conventional bikes?

A mile on an electric bike can be 20 times more carbon friendly than a mile on a conventional bike.

This perhaps unbelievable figure begins to make sense when you consider where you get your own body energy from.

For example, banana trees are many times less efficient at capturing the sun’s energy than solar panels. And only a small part of the banana tree’s energy finds its way into the banana itself, which then has to be transported halfway across the world to be eaten by us. This banana (or indeed any other food) is then used to ‘fuel’ the person who pedals a conventional bike. The higher the carbon footprint of the food you eat, the higher the carbon footprint of your cycle.

Your choice of food and drink powers a conventional bike, and electricity powers an electric bike. This might be another good reason to consider eating as much locally-produced food as you can if you love to cycle.

Electric motors are perhaps four times as efficient as human legs at turning chemical energy into bike propulsion.

Mike Berners-Lee predicts that if you charged an electric bike using solar power, this would beat the conventional bike by a factor of nearly 1000. As we haven’t conducted a specific study here in Guernsey, we can’t say for sure what the factor would be if we charged bikes at night using Guernsey’s imported renewable energy – but it would be quite significant.

In Guernsey, a proportion of the electricity you receive comes from solar power, generated both on-island and imported from the European grid. Annually this makes up over 90% of our electricity demand and includes renewable hydro and wind energy.

These figures are for a fully motorised electric bike, but by law electric bikes should be a pedal and motor-powered hybrid. This means the electric will assist, but doesn’t do all the work like an electric vehicle (EV) would. The real footprint of cycling an e-bike is somewhere between the footprint of conventional cycling (pedal power) and the figures for fully-motorised bikes

The added benefit is how electric bikes will help keep you fit while helping you get further, more quickly. .

Embodied CO²e emissions in an e-bike are similar to a regular bike, except for the added battery and engine. However per mile, e-bikes are often lower as you’re likely to ride the bike further over it’s entire lifetime than a conventional bike.

The e-bike’s battery turns out to account for just 0.5g CO²e per mile, as long as you use it to the end of it’s life. If you look after your battery carefully and get the recommended 1000 full charges out of it, it’s likely to be more carbon efficient.

To look after the battery, it’s best to trickle charge – re-charging it slowly – and neither let it run out totally flat or charge it to its maximum capacity. And don’t leave your bike out in our sea air for weeks on end unused – charge it up at night, get out and about and enjoy using it.

Did you know you can have an e-bike conversion that will convert your existing bike to an electric one?

How much carbon do bikes produce?

According to Mike Berners-Lee, a fully electric bike travelling at 12mph without any hills or stops may produce 3g CO²e per mile.

If you add in in five stops per mile and 20m of climbing, this would be roughly 5g CO²e per mile.

And as with all carbon calculations, you’ll have to consider the lifecycle emissions of the bike – including the embodied carbon of the bike model itself, which will add around 10-100g CO²e per mile.

Embodied carbon refers to all the carbon emitted when producing a bike, estimated from the energy used to extract and transport the raw materials, together with manufacturing and export emissions.

And if you’re wondering what CO²e means, this is short for ‘carbon dioxide equivalent.’ Put simply, this describes the bike’s overall contribution to global warming by taking into account the carbon dioxide (CO²) and other greenhouse gases (GHG) such as methane and nitrous oxide.

An electric bike’s battery should be added to this list too. If you charge between 9pm and 5am it’ll be less carbon intensive. And ideally, charge between 11pm and 5am to be cycling on 100% renewable energy

Charging - when is the least carbon intensive time?

In Guernsey, charging between 11pm and 5am (the green zone) means you can ride electric using 100% renewable energy.

This works best if you have a timer which automatically charges your battery during this green zone. One way you can do this is by investing in a smart plug or a plug-in timer which are wall-socket plugs that allow you to set a time you want anything that’s plugged into them to start.

If you have to charge it manually, you can still reduce your impact by charging from 9pm.

That’s because overnight is a quiet period on the electricity network and diesel generation at the power station is not needed to top up our electricity demand. This means we can use many appliances – such as electric bikes – using only the imported renewable energy.

And it will cost you* much less than charging earlier in the day

Be more sustainable while you sleep. Find out why it’s important to charge at night >

*If you’re on the Super Economy 12 tariff with a time band that starts on or before 9pm.

Avoid expensive peak times and charge your electric bike’s battery at night between 9pm and 5am – ideally, 11pm to 5am

What about e-bike conversions?

You can now convert your conventional bike into an electric-bike with just a few changes 

If you’ve got a really good bike or one you love to ride, it makes no sense to throw it out and spend money buying a new electric bike.

Electric bike conversions are fairly new on the scene but give people the option to keep their old bike, and hopefully get more out of them by making them electric.

This means you don’t need to consider the embodied carbon of a new bike and you’re giving a new lease of life to your current bike – just account for the relatively small carbon impact of the battery, engine, and electricity.

And make sure to charge it between 9pm and 5am – ideally, 11pm and 5am – so you aren’t relying on diesel-generated electricity for power.

E-bike conversions are a sustainable travel solution worth spending some time investigating.

One option you may have seen advertised on social media is the SwytchKit. This replaces your front wheel with a specialised wheel that contains a motor which drives the wheel to assist your cycle. A removable power pack sits on the front of your bike and uses a battery management system to power your bike and get you places.

E-bike batteries come with different power capabilities so make sure you ask any supplier if the bike they’re selling could get you up the Val Des Terres.

How much do e-bikes cost to run?

Electric bikes are one the cheapest ways to get places quicker while still getting some exercise in. 

Although designed for cars so won’t be an exact science for e-bikes, this calculator will give you an idea of how much it might to cost you to run an e-bike.

EV cost calculator 

You’ll need to enter figures for a petrol or diesel car which you can use to compare the cost difference between a e-bike commute and the same distance in a petrol or diesel car! The carbon figures should be ignored here as they’re based on calculations made for an electric vehicle.

For the distance, it’s best to look at how far a full charged electric bike can take you.

A battery with higher volts and amp hours will take you further than a similar model with a smaller battery so it’s best to get a steer on this first for an accurate figure.

Standard e-bikes with 400-500w batteries could take you up to 120km in one charge. E-bikes designed for longer distance cycling with 3kW batteries can reach around 400km.

The distance your e-bike can take you will depend on a number of factors including:

  • weather – sunny days often have longer range than rainy days
  • tyre pressure
  • weight carried (including battery weight)

This range assistant from Bosch will help give you a much better idea

Long cycling holidays or short everyday commutes? Batteries come in different sizes and buying a bike to suit your needs will make the most of your expenditure. 

Interested in an electric vehicle? Read more

51 Comments

Leave a Reply