CleanUp Technologies: Natural Gas

Natural gas is mainly comprised of methane (CH4). It can significantly reduce output of nitrogen oxide and particulates compared with diesel in certain applications. An additional advantage over the diesel engine is the very low engine combustion noise. This feature makes natural gas particularly suitable for vehicles operating in noise-sensitive locations (refuse vehicles, night time delivery vehicles).

Although a weight penalty is incurred due to the addition of high pressure tanks, certain operations are unaffected if the goods carried are volume rather than weight constrained.

Options are available for fuelling with either compressed natural gas (CNG) or liquefied natural gas (LNG), which are both available as road fuels in the U.K. LNG requires different, insulated (cheaper) fuel tanks and can deliver better range. There is currently limited availability of refuelling facilities for either of the fuels, though the national gas infrastructure makes the development of depot-based refuelling facilities a feasible option for medium-scale projects.

Both stoichiometric and lean-burn combustion can operate. The former, in conjunction with a three-way catalyst, will deliver lower nitrogen oxide. The latter will deliver better power, torque and fuel economy.

Durable methane catalysts are emerging which can give very low total hydrocarbon emissions at the tailpipe.

The CleanUp programme is supporting both re-engineered engines converted from diesel to NG operation and the re-engine option of removing the older diesel engine and substituting a new dedicated NG engine.