CNG is not worth the extra cost
This has been a bit of an issue for me for some years. I knew little about alternative transportation fuels before I came to BC – but then I had nearly three years doing little else. I had also been involved peripherally in the decisions about the future of trolleybuses in both Toronto and Hamilton – where compressed natural gas (CNG) was the preferred choice for replacements – so I have seen some of the ways these decisions have been made in the past.
There is a new “peer-reviewed, open-access journal that provides a platform for the dissemination of new practices and for dialogue emerging out of the field of sustainability” called “Sustainability: Science, Practice, & Policy”. In the first issue I have seen there is a comprehensive review of the data that should be driving these decisions. It is written by
Thomas Hesterberg and William Bunn [who] are employed by Navistar, a major manufacturer of diesel engines and vehicles. Charles Lapin is a consultant to Navistar. All authors declare no other financial interest in the subject matter of this study. Results and conclusions presented in this paper were drawn independent of the interests of the sponsor.
I thought I would put that in front. Navistar (who make International) do not – so far as I can determine – offer alternative fuel engines. But the paper “An evaluation of criteria for selecting vehicles fueled with diesel or compressed natural gas” does seem to be objective, is well referenced and – as noted above – peer reviewed.
The most frequent charge levelled at diesels is that they are “dirty” but the emissions from diesel engines have been subject to progressively stronger emissions regulations and new technologies have been developed which are now required to meet current standards. Since we only buy new buses (the last two excursions into the used bus market were mixed: Seattle does not maintain old buses like Everett) they meet these standards – and do so no matter what fuel they burn. Both diesel and CNG are fossil fuels – and several full life cycle cost analyses contradict each other on whether or not there is a ghg case one way or the other.
So the choice comes down to cost – and CNG is more expensive – and operational considerations which do not offset these costs but rather emphasize the case for diesel.
This region recently undertook a side by side comparison of CNG and other alternate fuels, including hythane (CNG with extra hydrogen added). Despite poor experience with previous fleets of CNG buses Translink bought more of them – the triumph of hope over experience. They simply hoped that the CNG converters had finally sorted out the problems of adapting a diesel to run on gas.
There are also hybrid buses on order. Again hybrids should offer much better fuel economy – after all they can capture energy lost by braking, and also reduce transmission energy losses – but full life cycle cost data will take some time to acquire as hybrid buses have been only recently available as production vehicles.
For many politicians, the venture into alt fuels was all about “spin” – not reality. For instance some of the first CNG buses got a special livery.
But the zero emissions trolleybuses that had been operating for years never got the “Clean Air Bus” treatment.Based on the data reviewed in the referenced article, the CNG buses were probably no cleaner than equivalent diesels. Yet they cost so much more that BC Gas (as it then was) organised a special deal to finance both the fleet and and its refuelling facilities so that the cost appeared to be similar to diesel. That is not good public policy. In the case of the trolleybus purchase, it was a much clearer decision. Yes trolleybuses were much more expensive – about twice the capital cost to buy, and they did not include the cost of the overhead as that was already in place – but it was worth that much more to get zero emission, nearly silent buses that could use electricity which in BC is nearly all from existing hydro. So no tail pipe emissions and negligible ghg - and the abilty to power the buses from what ever became available to Hydro in future.
But the case for CNG – which I never thought very compelling – seems now to be no longer in question. Even if the authors are thought to be biased by their employment, the evidence they present and the conclusions they draw seem to be quite sound. There really is no case for expensive “alternatives” which offer no real advantage.