"It is Crucial for Us to Keep an Eye on the Entire System"

Michael Mayer from Purem by Eberspächer speaks in the interview about new standards for the non-road sector, the use of hydrogen, and what difficulties farmland air quality poses. 

ATZheavyduty: Euro 7 is still a long way off in the field of agricultural machines. Are exhaust gas aftertreatment systems already being developed to comply with future standards or is an intermediate solution advantageous and cost-effective?

Mayer: In the Non-road Mobile Machinery (NRMM) sector, we are talking about the Stage V (Europe) emissions legislation and Tier 4 (North America) that have been in place since 2019. These define significantly stricter limits for pollutant emissions than the previous standards. The upcoming Tier 5 legislation applicable in the North American market from 2029 is expected to significantly tighten up pollutant emission limits from diesel engines, particularly with regard to NOX levels. There are no definitive statements regarding European legislation yet – it isn’t clear whether the limits of Stage VI will be oriented on Tier 5, or rather on the European Euro 7 standard for passenger cars and trucks. We always develop our exhaust gas aftertreatment systems according to market and customer requirements and provide support for component design to achieve the best possible reduction in pollutant emissions. This naturally includes alternative powertrain technologies that are necessary for decarbonization. We focused early on the adaptation of existing systems to alternative fuels and included further solutions in our portfolio to support this, especially for the fuel cell but also for electric vehicles.

How can the strict limits be complied with, particularly in the commercial vehicle and NRMM sectors?

A variety of customers already depend upon our portfolio to comply with the legislation currently in force and also with future legislation. We offer a range of solutions, for example, targeted heating of the catalyst, or an optimized injection strategy of the urea-water solution. In the USA, compliance with the strict legislation is only possible with our electrical heater for commercial vehicles. The EHC Fractal Heater very accurately increases the exhaust gas temperature during critical operating points to initiate the process of aftertreatment in time. It is also of interest for Tier 5 as it fulfills the NRMM requirements regarding robustness and performance with the smallest possible package.

The use of hydrogen means that many components such as fuel tanks and engines tend to be larger. Does this mean packaging for the exhaust gas aftertreatment is now an additional challenge?

Fuel tanks and engines using hydrogen tend to require more space than classic diesel applications. The exhaust gas aftertreatment must therefore be designed to be more compact, flexible, and thermally optimized without losing efficiency. This is exactly where we come into play: We develop modular aftertreatment systems that can be adapted for the tight mounting spaces – by employing integrated functions, space-saving geometries, or targeted thermal management designs.

The high pressure within the fuel tank is difficult to manage. How can this be solved and how is refueling with hydrogen done in the fields? 

Safely storing hydrogen and refueling is one of the largest technical hurdles facing an application in the agricultural sector— above all because machines with high energy requirements are often operated stationary far from infrastructure. The cutting edge of refueling is currently oriented on solutions in the commercial vehicle sector: Gaseous hydrogen is mostly refueled either at 350 or 750 bar via standardized interfaces. Over and above this, refueling with liquid hydrogen offers the advantage of a very high volumetric energy density that is ideal when there is little mounting space and a large need. Generally speaking, mobile refueling units, in container form for instance, are in field tests or are already in use in pilot projects, particularly in community fleets or in the construction sector. For agricultural applications, modular, locally available refueling solutions are conceivable in the future. Being a systems supplier for exhaust aftertreatment, fuel tank infrastructure does not belong to our core business – however, it is crucial for us to keep an eye on the entire system in order to be able to integrate technological interfaces in an intelligent manner.

The quality of the air in a field environment definitely does not comply with the required degree of cleanliness. Where are the technical issues in this case?

In an agricultural environment, the air is typically heavily contaminated with dust, pollen, ammonia, and other particles. It certainly does not comply by far with the requirements for cleanliness demanded by sensitive components such as fuel cells or precise air management systems. The challenge with fuel cells is mainly that even the smallest contamination can damage the membranes or interrupt the reaction process. Even the hydrogen engine is affected as contaminated air can influence combustion efficiency and the function of the downstream exhaust gas aftertreatment systems, albeit to a considerably lower degree than for the fuel cell. In technical terms, this means that highly effective, long-life filtration solutions are needed which are ideally self-cleaning along with monitoring systems and robust design against vibration, humidity, and temperature swings. Standards from the passenger car sector are not applicable in these harsh application environments; this is where application-specific solutions need to be developed.

Michael Mayer, many thanks for the fascinating discussion.

Read more of the interview in the ATZheavyduty issue 2/2025, to be published on October 17, 2025.