Understanding Your Vehicle's Carbon Footprint
Every time you fill up at a fuel station and drive, your vehicle releases carbon dioxide (CO₂) and other greenhouse gases into the atmosphere. Understanding where these emissions come from — and what can realistically be done about them — is increasingly important for informed consumers and policymakers alike.
Where Do Petroleum Emissions Come From?
Emissions from petroleum don't only occur at the tailpipe. The full lifecycle of fuel involves several stages, each with its own environmental impact:
- Extraction — Drilling and pumping crude oil from the ground. Methane leaks and flaring at wellheads contribute significantly to greenhouse gas emissions.
- Transportation — Moving crude oil by pipeline, tanker, or rail to refineries.
- Refining — Processing crude oil into petrol, diesel, and other products is energy-intensive and produces CO₂.
- Distribution — Transporting refined fuel to stations via road tankers.
- Combustion — Burning fuel in your vehicle's engine, which is by far the largest source of emissions in the chain.
Comparing Fuel Types by CO₂ Output
| Fuel Type | Approx. CO₂ per litre burned | Notes |
|---|---|---|
| Petrol (gasoline) | ~2.31 kg CO₂/litre | Standard combustion |
| Diesel | ~2.68 kg CO₂/litre | Higher energy density, fewer litres used |
| LPG | ~1.63 kg CO₂/litre | Lower carbon, less energy per litre |
| CNG (compressed natural gas) | ~2.04 kg CO₂/kg | Typically lower emissions per km |
Note: Per-kilometre emissions depend heavily on engine efficiency, not just fuel type.
What Can Individual Drivers Do?
While systemic change requires action at the industry and government level, individual driving habits genuinely affect emissions:
- Drive smoothly — Avoid harsh acceleration and braking. Smooth driving can reduce fuel consumption noticeably.
- Maintain correct tyre pressure — Under-inflated tyres increase rolling resistance and fuel use.
- Remove unnecessary weight — Every extra kilogram costs fuel.
- Use higher gears at appropriate speeds — Driving at lower RPMs reduces fuel burn.
- Avoid excessive idling — A parked engine running wastes fuel and produces emissions with no benefit.
- Choose the right vehicle — Fuel efficiency ratings vary enormously between vehicle models.
The Role of Biofuels and Fuel Blends
Many countries now mandate that petrol and diesel sold at the pump contain a percentage of biofuel — derived from plant material rather than fossil crude. The logic is that plants absorb CO₂ as they grow, partially offsetting the CO₂ released when the biofuel is burned. Common blends include E10 petrol (10% ethanol) and B7 diesel (7% biodiesel).
Biofuels are not without controversy — land use, water consumption, and food supply concerns are all valid criticisms — but they represent one available tool for reducing the carbon intensity of road transport fuels in the near term.
Looking at the Bigger Picture
Road transport is a significant source of greenhouse gas emissions globally, but it is far from the only one. Industry, heating, agriculture, and power generation all play major roles. Addressing petroleum emissions from vehicles is important, but it's most effective when pursued alongside broader decarbonisation efforts across the entire economy.