Is electrification the only decarbonization option for the bus and coach industry right now?

That’s a key question that will no doubt be asked at the National Bus & Coach Show at Brisbane’s Exhibition Centre from September 17-18 as the optimism and uncertainties of the future collide with the realities of the moment.

While battery electric vehicles may eventually dominate the landscape, the current limitations of vehicle cost, range and supporting infrastructure still need to be addressed.

The road to zero emissions is long and lined with questions that will no doubt see transitory solutions like advanced internal combustion engines (ICE), hybrid technologies and alternative fuels playing a role.

At the recent Advanced Clean Transportation (ACT) Expo in Las Vegas, Accelera by Cummins – the zero-emissions business unit of Cummins Inc. –  displayed a full line-up of differing technologies, including more powerful versions of its hydrogen fuel cell engines, a high-efficiency eAxle and its next-generation batteries.

While there were plenty of headlines from the displays at ACT Expo, the reality is that Cummins is still investing heavily in internal combustion technologies for increasingly stringent emissions standards.

Fuel agnostic engines

While the X15 may dominate the headlines for heavy road transport, two products that will be of special interest to the bus and coach industry are the B6.7H and X10, both part of Cummins’ industry-first fuel agnostic platform.

While each engine will be able to run on hydrogen and natural gas, Cummins states that diesel will remain a critical technology for the on-highway market for years to come, and the company will continue to support it.

“We are committed to advancing diesel technology while our markets and our customers need it to run their businesses,” said José Samperio, Executive Director – North America On-Highway at Cummins.

The brand new X10, available as a diesel initially with ratings from 320-450 hp, will be compliant with the US EPA’s 2027 regulations while providing a step-change in fuel economy improvement.

The B6.7H hydrogen internal combustion engine, scheduled for release in the 2026-2027 timeframe, delivers performance similar to that of Cummins’ 6.7-liter diesel engine with peak outputs of 290 hp and 885 lb ft of torque.

“While Cummins is investing in a range of power options to support decarbonization, hydrogen internal combustion engines are emerging as a key technology to eliminate carbon emissions from the transport sectors, while retaining the power density typical of diesel engines,” said Jim Nebergall, general manager of hydrogen engines at Cummins.

Hydrogen has some way to go to reach its full potential as a zero-carbon fuel, the obvious requirement being for adequate infrastructure to produce green hydrogen in quantities that make it accessible and affordable. 

Alternative fuels

The near-term opportunities from the use of lower-carbon alternative fuels are also significant.

Cummins has approved the use of unblended renewable diesel, including hydrotreated vegetable oil (HVO), for its on-highway diesel engines (B6.7, L9, X12 and X15) with no engine modifications required for a 100% blend.

Utilizing renewable diesels like HVO reduces net greenhouse gas (GHG) emissions by up to 90% compared to conventional diesel. Particulate matter emissions are also reduced dramatically, potentially by up to half.

Biodiesel is another lower-carbon fuel that can easily be integrated into a fleet's engines. Manufactured from vegetable oils, animal fats or recycled restaurant grease (used cooking oil), biodiesel is a renewable, biodegradable fuel with properties similar to those of diesel.

Cummins on-highway engines built after 2007 are compatible with B20 biodiesel (20% biodiesel, 80% petroleum diesel), a blend that is capable of reducing greenhouse gas emissions, namely CO2, by around 15%.

At the National Bus & Coach Show in Brisbane in September, Cummins will feature an ultra-low emission L9 Euro 6 diesel engine along with the BP107E battery from Accelera. The BP107E features Lithium Iron Phosphate (LFP) chemistry which enables longer battery life and faster charging capabilities for reduced vehicle downtime.