Sustainability

Methane for engine propulsion

Methane is also an ecological fuel used for engine propulsion. In fact it is a fuel with a low carbon content, which does not contain aromatic compounds, sulphur and lead. Methane cars, compared to petrol cars, release 25% carbon dioxide less, contributing therefore to the reduction of the “greenhouse” effect and above all they do not produce particulate (made up of quite dark particles that look like smoke or soot, but so small that they can only be looked at the microscope), benzene and other aromatic compounds. They also produce lower quantities of carbon monoxides, nitrogen oxides and un-burnt hydrocarbons (combustion residual hydrocarbons are mainly made up of carbon). The emission of sulphur dioxide, main cause of acid rain, is negligible. There are many advantages for human health (while many hydrocarbons are dangerous for human health). In particular, the most reactive hydrocarbons in the presence of nitrogen oxides and solar light can generate ozone at low altitude, i.e. a very irritating gas for the breathing system, which can provoke photochemical smog. Instead, benzene and other polycyclic aromatic hydrocarbons (PAH) are considered as potentially carcinogenic. Car traffic contributes a lot to total PAH emissions, especially in urban areas with a high traffic density, in particular in those areas where the urban conformation (traffic lights, road crosses, etc) forces to drive with the engine on all the time. Thanks to modern technological solutions applied to engines, the emissions of these substances produced by methane vehicles are very low, or like with benzene, they are absent. In order to make a comprehensive comparison between methane and traditional fuel cars, it is necessary to consider the environmental impact along the whole energy processing cycle, therefore also that part of the energy chain that is related to the extraction, production and transport of fuels. The analysis should also consider other factors, like the availability of energy sources to be used in the near future. The aim of these studies is to direct consumptions towards a more efficient use of energy sources both from the energy and environmental point of view. In particular, the methane cycle has some features as compared to other liquid fuels that bring further environmental advantages. The methane can be directly used as a fuel immediately after the extraction and after common filter treatments. It does not require any refining. It is handled through the methane pipelines: it is therefore available with continuity in petrol stations, without the need to accumulate it in storage centres, and without any impact on traffic and surface transport. The supply system of vehicles allows to avoid evaporation losses as it occurs with other liquid fuels. In terms of costs (considering both the cost of the fuel and the vehicle consumption) it was calculated that the user spends almost 60% less than with petrol and 30% less than with gas oil. In Italy an agreement between the Ministry for the Environment and protection of the territory, Unione Petrolifera and Fiat has established a national programme from 2002 and 2005 that plans to use methane for urban transport in the main cities.