Travel · emission factor
The Carbon Footprint of Cycling and Walking
0 g CO₂e / km
Cycling and walking produce 0 g CO₂e per kilometre of direct emissions — no fuel is burned and no tailpipe exists. Compared with 231 g/km for a petrol car or 255 g/km for a plane, active travel is the lowest-carbon way to move that exists. For short urban trips, which make up a large share of all car journeys, it is usually the single easiest substitution a person can make.
Why the footprint is effectively zero
Walking and cycling are powered by human metabolism rather than combustion or grid electricity, so the in-use emission factor is 0 g CO₂e per passenger-kilometre. Lifecycle analyses do attribute small amounts to bicycle manufacturing and to the extra food energy a rider burns — typically estimated in the range of a few tens of grams per kilometre depending on diet — but even generous accounting leaves a bike far below every motorised mode. There is no engine idling, no cold starts, no tire and brake particulate at car speeds, and no fuel supply chain. A bicycle also lasts many years and thousands of kilometres, so its embodied manufacturing emissions are spread very thin. For practical comparison and tracking purposes, 0 g/km is the standard convention used by transport agencies.
How active travel compares with other modes
The contrast with motorised transport is stark. A petrol car emits 231 g CO₂e per passenger-km and a diesel car 192 g; a bus averages 105 g, a train on a low-carbon grid about 20 g, and even an electric car on clean electricity carries roughly 8 g/km from tire and brake wear. Replacing a daily 5 km each-way car commute with cycling avoids about 2.3 kg of CO₂e every workday — on the order of half a tonne per year. Transport accounts for roughly a quarter of global energy-related CO₂ emissions, and road vehicles are the largest share of that, which is why cities from Paris to Copenhagen treat cycling infrastructure as climate policy, not just mobility policy.
Where switching matters most
The biggest wins come from short trips, because that is where cars are least efficient and bikes are most competitive. In many European countries, around half of car journeys are under 5 km — a distance most people can cycle in 15–20 minutes and where a cold engine runs at its dirtiest. E-bikes extend the practical range to 10–15 km and hilly terrain while adding only a few grams per kilometre of electricity; they still dramatically undercut any car. Active travel also stacks co-benefits that motorised modes cannot: better cardiovascular health, zero local air pollution, less noise, and far less urban space consumed per traveller. The main constraints are infrastructure and habit rather than technology.
How bicycle & walking compares
g CO₂e / km · data as used in the Decarbonr app · sources: European Environment Agency, IPCC
How to reduce this footprint
- ✓ Replace car trips under 5 km with walking or cycling first — short trips are where cars pollute most per kilometre.
- ✓ Consider an e-bike for longer commutes or hills; its electricity use adds only a few grams of CO₂e per kilometre.
- ✓ Combine modes: cycle or walk to a train station instead of driving, cutting the highest-emission leg of the journey.
- ✓ Log your walking and cycling trips in a tracker like Decarbonr to see the emissions you avoid accumulate over time.
Frequently asked questions
Is cycling really zero carbon if you count food and manufacturing?
Direct emissions are genuinely 0 g CO₂e/km — nothing is burned. Lifecycle studies add roughly 15–35 g/km for bike manufacturing and extra food energy, depending on diet. Even at the high end, that is a small fraction of a petrol car's 231 g/km.
How much CO₂ do I save by cycling instead of driving?
Every kilometre cycled instead of driven in a petrol car avoids about 231 g CO₂e, or 192 g versus a diesel car. A typical 10 km round-trip commute by bike avoids around 2.3 kg per day, which adds up to roughly half a tonne over a working year.
Is an e-bike still low carbon compared with an electric car?
Yes. An e-bike uses about 1 kWh per 100 km, translating to only a few grams of CO₂e per kilometre on most grids. An electric car still carries around 8 g/km from tire and brake wear alone on a clean grid, plus far higher manufacturing emissions per passenger.
Track this automatically
Decarbonr turns meals and journeys into one clear daily CO₂e number — on your iPhone, on-device, private by design.
Free trial · then subscription · AI scanning optional add-on
Sources & methodology: see Research & scientific references. Figures are averages used by the Decarbonr app; real-world values vary by production system, country, and occupancy.