How Much CO₂ Can a Single Electric Bus Save Annually?
Electric buses are emerging as a sustainable alternative to traditional diesel buses, offering significant environmental and economic benefits. One of the key advantages of electric buses is their ability to reduce carbon dioxide (CO₂) emissions, which contribute to climate change and air pollution.
This article provides a detailed analysis of how much CO₂ can a single electric bus save annually, compares emissions with diesel buses, examines the challenges in transitioning to electric buses, and explores strategies to overcome these barriers.
Also Read: Top 5 Electric Buses at the Bharat Mobility Expo
CO₂ Emissions: Diesel vs. Electric Buses
A standard 12-meter diesel bus, widely used in public transportation, typically operates under the following parameters:
- Fuel efficiency: Approximately 2 km per liter of diesel.
- Annual distance traveled: Around 75,000 km.
- CO₂ emissions per liter of diesel: 2.68 kg CO₂.
An electric bus runs on electricity, with the following specifications:
- Energy consumption: 1 kWh per km.
- Annual distance traveled: 75,000 km.
- CO₂ emission factor of India’s electricity grid: 0.60 kg CO₂ per kWh (subject to variation based on energy sources).
Annual CO₂ Emissions Comparison
| Bus Type | Fuel/Energy Consumption | Annual Distance (km) | CO₂ Emissions per Unit | Total Annual CO₂ Emissions |
|---|---|---|---|---|
| Diesel Bus | 2 km/l | 75,000 km | 2.68 kg CO₂ per km | 201,000 kg (201 tonnes) |
| Electric Bus | 1 kWh/km | 75,000 km | 0.60 kg CO₂ per km | 45,000 kg (45 tonnes) |
Note: CO₂ emissions per km for diesel buses are calculated based on fuel consumption and CO₂ emissions per liter of diesel. For electric buses, emissions per km are calculated based on energy consumption and the CO₂ emission factor of the electricity grid.
Thus, an electric bus reduces CO₂ emissions by approximately 156 tonnes per year when replacing a diesel bus. If powered entirely by renewable energy, the CO₂ savings can reach 201 tonnes per year.
Breakdown of CO₂ Savings
1. Reduced Tailpipe Emissions
- Diesel buses release direct tailpipe emissions, including CO₂, nitrogen oxides (NOx), carbon monoxide (CO), and particulate matter (PM), all of which contribute to air pollution and adverse health effects.
- Electric buses, in contrast, produce zero tailpipe emissions, improving urban air quality and reducing respiratory diseases caused by vehicular pollution.
2. Lower Emissions from Energy Use
- While electric buses rely on electricity from the grid, their emissions are significantly lower than those of diesel buses.
- The carbon intensity of electricity generation determines the true CO₂ savings of an electric bus.
3. Impact of Electricity Generation on CO₂ Emissions
| Energy Source | CO₂ Emissions per kWh (kg) |
|---|---|
| Coal Power | 0.90 – 1.10 |
| Natural Gas | 0.40 – 0.50 |
| Hydropower | ~0.00 |
| Solar & Wind | ~0.00 |
If an electric bus is charged using 100% renewable energy, its operational CO₂ emissions will be nearly zero.
4. Regenerative Braking and Energy Efficiency
- Electric buses utilize regenerative braking, which recovers energy lost during braking and converts it into electricity.
- This system improves overall energy efficiency, reducing electricity consumption by 15-25% and lowering CO₂ emissions.
Fleet Electrification and CO₂ Savings at Scale
The transition to electric buses on a large scale has the potential to significantly reduce national and global CO₂ emissions. For instance, if 1,000 diesel buses are replaced with electric buses, annual CO₂ savings would amount to:
- 156,000 tonnes of CO₂ per year in India, based on the current energy mix.
- Up to 201,000 tonnes of CO₂ per year if the electricity grid shifts entirely to renewable energy.
The impact of widespread electric bus adoption has already been observed in cities such as:
- Shenzhen, China, which transitioned to an all-electric bus fleet, reducing emissions by approximately 1.35 million tonnes of CO₂ annually.
- London, United Kingdom, which has integrated electric buses into its public transport system to meet its net-zero carbon goals.
- Delhi, India, which is scaling up its fleet of electric buses as part of its broader clean mobility strategy under the PM E-DRIVE scheme.
Challenges in Transitioning to Electric Buses
1. High Initial Investment Costs
- Electric buses cost 1.5 to 2 times more than conventional diesel buses.
- Cost of a 12-meter electric bus: ₹1.5-2.5 crore ($180,000-$300,000).
- Cost of a diesel bus: ₹75 lakh-₹1 crore.
- Additional expenses include charging infrastructure, battery replacement, and grid upgrades.
2. Charging Infrastructure Limitations
- Lack of widespread charging stations hinders large-scale deployment.
- Fast-charging stations require high power capacity, increasing electricity demand.
- Charging time varies from 30 minutes (fast charging) to 6 hours (slow charging), affecting operational efficiency.
3. Battery Performance and Longevity
- Lithium-ion batteries degrade over time, requiring costly replacements every 6-8 years.
- Battery efficiency is affected by extreme weather conditions, reducing the operational range.
4. Grid Capacity and Energy Demand
- Large-scale electrification of buses will increase electricity demand, necessitating grid upgrades.
- Peak-hour charging can strain the grid if not managed efficiently.
5. Lack of Standardization and Policy Implementation
- Different charging connectors and battery technologies create compatibility issues.
- Inconsistent policies across states slow down procurement and deployment.
6. Disposal and Recycling of Batteries
- Battery disposal and recovery of lithium, cobalt, and nickel remain a logistical challenge.
- Proper end-of-life management of batteries is essential to prevent environmental hazards.
Strategies to Overcome Transition Challenges
1. Financial Incentives and Cost Reduction Strategies
- Government subsidies and tax incentives can reduce the initial cost burden.
- Battery leasing models allow operators to pay for batteries separately, reducing capital costs.
2. Expanding Charging Infrastructure
- Investment in widespread fast-charging stations along major bus routes.
- Battery swapping technology to minimize downtime.
- Integration of solar and wind power with charging stations to reduce dependence on fossil-fuel-based electricity.
3. Advancements in Battery Technology
- Research on solid-state batteries to improve range and durability.
- Temperature control systems to mitigate the impact of extreme weather on battery efficiency.
4. Grid Modernization and Smart Charging
- Smart charging systems to optimize energy use and prevent grid overload.
- Decentralized solar-powered charging hubs to reduce emissions from electricity generation.
5. Standardization and Policy Reforms
- Establishing uniform charging standards to improve interoperability.
- Long-term policy commitments to encourage private investment.
6. Circular Economy for Battery Recycling
- Developing battery recycling facilities to recover valuable materials.
- Exploring second-life applications for retired batteries in energy storage systems.
Also Read: Electric Bus Sales in India in February 2025: A Detailed Market Analysis
The transition to electric buses offers substantial environmental benefits, with a single electric bus saving up to 156 tonnes of CO₂ per year, and 201 tonnes per year if powered by renewable energy. While there are challenges in implementation, solutions such as financial incentives, charging infrastructure expansion, battery advancements, and policy standardization can facilitate a smooth transition.
Electric buses represent a critical step toward sustainable urban mobility. With proper investment and planning, their widespread adoption can significantly contribute to decarbonizing public transportation and achieving long-term climate goals.
