Zero-Emission Buses: How to Transition your Transit Fleet from CNG

2 minute read
Mar. 16, 2017
Article by Nicolas Pocard

Planning to transition a transit fleet from CNG to zero-emission buses?

Think about the fueling/charging infrastructure.

Many transit authorities, having invested in low-emissions compressed natural gas (CNG) powered buses, are now looking to drive bus emissions to zero, by adding zero-emission buses (ZEB) to their fleets.  

Zero emission bus in London, UK

Image credit: Geograph

How Do Different Types of Zero-Emission Buses Compare?

What are the ZEB options? There are two technologies:

  • battery powered electric buses
  • hydrogen fuel cell electric buses (FCEB)

Both technologies deliver on the zero-emission mandate. Both technologies are proven in the daily grind of real-world transit systems. But only FCEBs offer the critical advantages of:

  • longer range
  • better cold weather performance
  • superior hill climbing ability
  • faster refilling

While battery powered electric buses are less expensive to purchase, their operating range can limit implementation. Longer or hilly routes that CNG buses handle with ease can be impractical with battery-powered buses. And in extreme weather conditions, battery power is reduced, for shorter operating ranges and less climbing power.

Only fuel cell electric buses are a one-for-one direct replacement for CNG bus routes, offering similar range and operability.

Refueling Infrastructure Affects Total Deployment Costs

Unlike battery electric buses that require a total replacement of the existing fueling infrastructure, FCEBs can use hydrogen generated from a fuel feedstock common to CNG buses (natural gas).

For hydrogen fuel cell electric buses, the hydrogen refueling network can be developed by leveraging the existing CNG network.

  • CNG and FCEB buses have similar operating ranges, so same routes can be operated with no additional buses. CNG and FCEB buses both require the refuelling of a compressed gas, with similar piping, compression, and gas distribution equipment
  • Codes and standards are similar (for the safe handling of Class 2 flammable gasses)
  • CNG and hydrogen use a common feedstock – natural gas - so much of the existing infrastructure can be repurposed
  • Like CNG, hydrogen refuelling infrastructure is scalable and allow fast refilling of transit buses
  • Maintenance personnel is already trained to handle gas as a fuel for buses

In California, CNG and FCEB co-exist in a phased-in transition

Two transit operators have begun the transition from CNG to hydrogen fuel cell buses. Sunline Transit in Cochella Valley and OCTA Transit in Orange County California have mixed CNG and FCEB fleets.


If you’re planning on making the transition from CNG to zero emission buses, you’ll need to consider the different types of ZEBs available. Although all ZEBs can help you meet the zero emissions mandate, hydrogen fuel cell buses have the advantage in that they can operate like CNG buses using similar scalable refuelling infrastructure.

Join in the conversation. What are your thoughts on making the transition from CNG to zero emission buses?


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