Is liquefied natural gas an alternative to non-electrified rail traction?

In order to reduce the environmental impact of fossil fuel consumption, the rail transport sector is analysing various alternatives for non-electrified lines. As an alternative to diesel, this study analyses the use of Liquefied Natural Gas (LNG) in rail traction. A predictive model is developed that estimates emissions on different routes. The model is fitted with real data obtained in pilot tests. In these tests, a train with two engines, one diesel and one LNG, was used. The methodology is applied to assess the impact on consumption and emissions of the two fuels on a narrow-gauge commuter line. A significant improvement is observed in some indicators, while in others the differences are minor. The conclusions that can be drawn are that operational CO2 (greenhouse gas) emissions are lower in the LNG engine than in the diesel engine; CO emissions are lower in the diesel engine and emissions of other pollutants (nitrogen oxide and particulate matter) are higher in the diesel engine by several orders of magnitude.