Methane Emission Control A review of mobile and stationary source emissions abatement technologies for natural gas engines

Natural gas is of increasing interest as an alternative fuel for vehicles and stationary engines that traditionally use gasoline and diesel fuels. Drivers for the adoption of natural gas include high abundance, lower price and reduced greenhouse gas emissions compared to other fossil fuels. Biogas is an option which could reduce such emissions further. The regulations which cap emissions from these engines currently include Euro VI and the US Environmental Protection Agency (EPA) greenhouse gas legislation. The regulated emissions limits for methane, nitrogen oxides (NOx) and particulate matter (PM) for both stoichiometric and lean burn compressed natural gas engines can be met by the application of either palladium-rhodium three-way catalyst (TWC) or platinum-palladium oxidation catalyst respectively. The drivers, policy and growth of this Pd based catalyst technology and its remaining challenges to be overcome in terms of cost and catalyst deactivation due to sulfur, water and thermal ageing are described in this short review.