Searching for alternative fuels does not only concern individual homes and private car owners – the issue is increasingly recognised by both city and municipal authorities considering ways to reduce the environmental impact of public transport, as well as by automotive companies competing with each other to provide new solutions. LNG buses entered the European market in 2013 with the first such bus in the streets of (and here’s a surprise) Olsztyn. What do we know today, having been using such vehicles for 9 years?

Why LNG and not CNG?

Both abbreviations refer to natural gas – the difference is in the physical state. CNG is compressed gas and LNG is liquefied gas. In the first quarter of 2022, there were around 850 buses powered by natural gas on Polish streets. The advantage of LNG lies in the ease of its use on one hand and its safety on the other.

CNG-powered buses need special design solutions – first and foremost an extremely resistant tank in which the compressed gas will travel until it is burned. Not only does the tank have to be armored, but also large, as CNG has a considerable volume. Meanwhile, due to its much higher density, LNG will fit into a smaller tank and is safer to transport. The refueling itself also takes less time and the bus will cover a longer distance than with CNG.

It must be clearly emphasised that from the point of view of ecology, both LNG and CNG are a much better options than diesel, traditionally used in buses or trucks. In the meantime, however, let us concentrate on LNG.

Benefits of LNG

Natural gas is described as a clean fuel, so a bus powered in this way contributes significantly less to smog. This is extremely important especially in colder months, when fumes from the chimneys of detached houses trouble our lungs too much anyway.
The weight of a full tank (almost identical to a tank filled with diesel) and its location (in the rear of the bus, near the engine compartment), do not increase the weight of the vehicle and do not shift its centre of gravity, which contributes to safety. Refueling is quick (about 6 minutes) and power and distance are comparable to those obtained from diesel, so much higher than in the case of electric motors.
In addition, it is worth remembering that methane, which makes up more than 90% of the LNG composition, is a waste product from coal mines. Instead of its excess being disposed through combustion, it can be much more useful – to power vehicles.

Downsides of LNG – few, but present

Let us add, for fairness, a spoonful of tar to this barrel of honey (or rather liquefied gas). LNG does not do well in very high temperatures – on hot days, the bus will burn much more than in standard weather conditions. Longer period out of operation of the vehicle is also inadvisable – LNG loses energy and there may be situations where the whole tank simply needs to be replaced.
An LNG-powered bus is also more expensive, although not drastically, than a CNG-powered bus (both, on the other hand, are cheaper than electric buses and more expensive than classic diesel vehicles).

LNG may be a solution for cities struggling with smog. As usual, the devil is in the detail – in this case in adapting the infrastructure and replacing the fleet as quickly as possible, especially diesel vehicles.

Marta Nowak

Reference list:
Gaz LNG – paliwo przyszłości w transporcie drogowym?
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Pierwsze w Europie autobusy zasilane LNG wyjechały na ulice Olsztyna.
Polski rynek autobusów CNG/LNG w Polsce w I kwartale 2022.
W. Wolański. LNG – ekologiczne paliwo w autobusach marki Solbus. Combustion Engines. 2012, 1, 113-117.
M. Ziembicki, D. Pyza. Paliwa alternatywne w transporcie publicznym i wynikające z ich eksploatacji ograniczenia. Scientific papers of the Warsaw University of Technology. Transport. 2018, 121, 441-451.