On the barricades for CNG – a polemic

In his article published on 28 October 2008 in the NRC Handelsblad daily newspaper, Mr Steinbuch proposes that modern buses running on natural gas are worse polluters than their modern diesel counterparts. This article is a garbled mess of facts, hearsay and erroneous statements.

The first line already contains the first falsehood: although we might wish for there to be as many as several hundred buses running on natural gas on Dutch roads, in Haarlem there are currently around 85 such buses in operation, and up to a few dozen in the rest of the Netherlands (e.g. in Groningen and Ede-Wageningen). This number is growing slowly but steadily. Around three hundred buses in total will be deployed in the bus public transport area of The Hague and Haaglanden that has just been contracted.

Steinbuch also discusses the conversion of buses to natural gas, a process which is now already quite obsolete. Nowadays, buses running on natural gas are delivered ex-factory by several European manufacturers, and with a range of technical specifications.

It is precisely this last aspect that makes it difficult to compare buses to one another. There are both diesel and natural gas buses that conform to the European Emission (EEV) standards. It is not possible to simply state that diesel buses score better on all parameters except for NOx, as differences in length, weight, maximum number of passengers, etcetera make the buses difficult to compare. Lighter buses will, without a doubt, produce less emissions. However, these buses generally also have a lower passenger capacity, meaning that the emissions could very well be higher per passenger-kilometre.

NOx is a collective parameter for various nitrogen molecules. Emission measurements used for the approval of various vehicle types only establish NOx. However, NO2 is the most important criterion for measuring air quality. The percentage of NO2 in diesel bus NOx emissions is known to be very high. Buses running on natural gas emit up to fifty per cent less NOx than diesel buses and little to no NO2, yielding major benefits for air quality. Fine particle emissions from buses running on natural gas are at a level comparable to that of EEV diesel buses.

Steinbuch’s argument claiming a forty per cent lower energy rating for buses on natural gas, is therefore negated. And that is beside the fact that the energy rating is twenty per cent lower than diesel, not forty per cent. What is more: it emphasises the potential of this intrinsically clean fuel.

Many governments invest in natural gas as an engine fuel in order to realise several objectives at the same time. They support the achievement of air quality targets by opting for natural gas and striving to reduce CO2 emissions. Choosing natural gas brings us closer to the next step in the transition process, namely biogas or ‘green gas’. Biogas is not affected by the ‘food-fuel issue’ because it can be (and is already) produced from waste products such as biodegradable waste, manure, sewerage treatment sludge, and in the long term also wood-based biomass. This will reduce CO2 emissions per kilometre driven by eighty to a hundred per cent. Put briefly, the transition from natural gas to biogas is a very logical and politically responsible policy decision.

It goes without saying that using natural gas as a vehicle fuel requires investments. The buses are more expensive and investments are needed for the refuelling infrastructure. However, the cheaper fuel means that the investments will pay for themselves – not to mention the avoided costs. Although intrinsically clean technology and fuels may cost more, cleaning up afterwards is always more expensive. Adaptation measures cost many many millions, particularly for a country like the Netherlands, half of which lies below sea-level.

I would like to voice my agreement with Lodewijk de Waal, who recently pleaded for any support for the ailing European automobile industry to be given only in return for a decrease in CO2 emissions. I would even go one step further: because the reduction of CO2 emissions is not only dependent on engine technology, the automobile industry ought to be making structural investments in vehicles that are suitable for biofuels as well as hybrid, electricity and hydrogen-based fuel sources. If the government includes this form of CO2 reduction in its tax policy, it could encourage the sale of such vehicles and reduce the impact that our mobility needs have on the environment.

Related article

A CNG bus is clean. A diesel is even cleaner