The comeback of the trackless trolley

The trackless trolley - or the trolleybus as it is called in Europe - is scheduled for a comeback.

The diesel bus emit carcinogenic particulates which may account for several thousands of cancer deaths in major cities. It is true that recent developments of emission technology has reduced the toxic emissions, but diesel exhaust is still the major contributor to high levels of nitrogen oxides and fine particulates in city centers.

Ethanol and natural or bio gas can also fuel buses, but the use of ethanol and gas fuels will also contribute to the environmental impact. Extensive production of ethanol from sugar cane in countries like Brazil is a danger to the rainforests. Natural or biogas is to 95-98% constituted of methane. Part of the methane is emitted and methane emissions are a powerful contributor to global warming since the 'greenhouse effect' is 17-20 times higher than that of carbon dioxide, CO2.

Electricity can be produced without emissions from a variety of sources like hydro, wind and nuclear. A comeback for nuclear energy - as suggested by Pres. Bush recently - will increase the odds of the trackless trolley as a means of transportation in the big cities.

Trackless trolleys are cheaper to install than light rail and other rail systems. They can be included in a 'Bus Rapid Transit' scheme with segregated busways.

They survive in 7 North American cities, and several hundred European. Once they were introduced as substitutes for streetcars in many cities.

San Francisco has the most extensive network of trackless trolleys in North America. It is constantly being extended, and is comprised by 17 lines. In addition to the trackless trolleys, San Francisco has several other environmentally sound transportation systems like cable cars, light rail, streetcars, subways and commuter rail. All the electric energy consumed by the trackless trolleys in SF comes from hydroelectric power - a clean energy source without any harmful emissions.

Seattle has a smaller network of trackless trolleys. Other cities in the US with trackless trolleys include Dayton, Boston and Philadelphia. Philadelphia recently decided to invest in new trackless trolleys in their southern suburbs where traffic was suspended for a number of years.

In Canada, Vancouver has an extensive network of trackless trolleys. The city of Vancouver also recently decided to invest in a large batch (more than 200) of new trackless trolleys of a futuristic design, and the first buses are delivered right now. Edmonton is the other Canadian city with trackless trolleys. They will soon have to decide about the future for the system, but environmental groups are optimistic that the city will invest in new trackless trolleys of maybe the same kind as in Vancouver.

The trackless trolley is cheaper than diesel buses given that the traffic density is sufficient. The life span of a trackless trolley is about double that of a diesel bus. Even if a trackless trolley is more expensive to buy due to the few items produced the capital costs as well as the running costs are lower. A trackless trolley uses about 2 kwh/km of electric energy compared to 0.5 liters of diesel per km for a diesel bus. In especially Europe, this means much lower energy costs for the trackless trolley.

So, when diesel prices are expected to rise further, while gas and ethanol prices also are high, the trackless trolley might be an environmentally attractive alternative for more and more cities sized 50.000 inhabitants and up. This is true both for North America and for Europe.


Bo Persson

Is methane the big danger?

The world politicians efforts on combatting global warming is concentrating on reducing carbon dioxide (CO2) emissions.

But is that really so important compared to methane (CH4)?

The 'relative greenhouse effect' of methane is estimated at about 17 times that of carbon dioxide. In cold climate, the ratio may be as high as 40 times that of CO2. But it is true that the emissions of carbon dioxide still are much greater than those of methane. So the 'historic' global warming effect that we have seen might be caused largely by carbon dioxide.

However, the emissions of methane are increasing on a much faster rate than those of carbon dioxide. It is no doubt that global warming in the future more and more will be associated with methane.

In addition, the use of methane-containing fuels is even advocated by environmental interests. The methane in the atmosphere come from a variety of sources, among those most important are agriculture, garbage dump sites, exploration of natural gas fields, pipelines for natural gas, leakages from gas depots or gas filling stations, emissions from end use of natural gas or biogas in household, industry or vehicles.

The fact is that natural gas as well as 'biogas' contain 95-98% methane. Environmental organisations use to promote the use of 'biogas' as an alternative to fossil fuels. However, the CH4 emissions must be taken into consideration. 'Biogas' is often produced from garbage or harvested grass that is anaerobically treated. If not biogas was produced, some methane would anyhow be produced from the dump site but the majority of the coal-containing compounds would be transformed into other hydrocarbons or just carbon with time. So there is a considerable net emission of methane (and also carbon dioxide) if biogas is produced and used in vehicles. Still worse is of course the use of natural gas in vehicles and other applications.

The use of natural gas - or biogas - in vehicles is usually associated with significant emissions of methane due to that engines are tuned in to reduce emissions of nitrogen oxides which otherwise would be a problem for gas-powered vehicles. This is especially true for cold starts and during city traffic conditions.

A recent Swedish study published by the Environmental Protection Agency in Sweden gives the following emission parameters for biogas- and diesel-powered vehicles (Framtida mojligheter med nya drivmedel, Naturvardsverket 2004):

Diesel; CO2: 3,500 mg/MJ (emissions from tailpipe incl. production of fuel)
Biogas; CH4: 640 mg/MJ (emissions from tailpipe incl. production and storage of fuel)

In this study, the biogas-powered vehicle contributes 3-6 times more to the immediate greenhouse effect by its methane emissions than the diesel vehicle by its CO2 emissions considering that the relative effect of methane is 17-40 times that of CO2.

However, methane is more short-lived in the atmosphere. But still, biogas vehicles seem to contribute more to global warming than diesel vehicles. The methane emissions from diesel vehicles are very low; in this study only 2 mg/MJ (1/300 of the biogas vehicle).

This is thus a contradiction - that environmental organisations call for the use of gas-powered vehicles when methane emissions might become the most significant global warming problem in the future.

If we cannot control the methane buildup in the atmosphere there might be more severe effects as methane is released from 'frozen' deposits at sea bottom when the water warms up. The resulting greenhouse effect might be much worse than what we are now discussing - there might be an increase in global temperatures of 20-30 degrees C which in fact has happened historically, last time during Eocene period som 55 million years ago when the North Pole had a climate with temperatures about +20 degrees C and of course no ice.

So try to stop the methane emissions before it is too late. Use cheap power from nuclear energy instead of natural gas or biogas wherever feasible. Use electric vehicles in cities with zero emissions instead of experimenting with gas-powered vehicles.


Bo Persson