Greenhouse Gas and Noxious Emissions from Dual Fuel Diesel and Natural Gas Heavy Goods Vehicles

Dual fuel diesel and natural gas heavy goods vehicles (HGVs) operate on a combination of the two fuels simultaneously. By substituting diesel for natural gas, vehicle operators can benefit from reduced fuel costs and as natural gas has a lower CO₂ intensity compared to diesel, dual fuel HGVs have the potential to reduce greenhouse gas (GHG) emissions from the freight sector. In this study, energy consumption, greenhouse gas and noxious emissions for five after-market dual fuel configurations of two vehicle platforms are compared relative to their diesel-only baseline values over transient and steady state testing. Over a transient cycle, CO₂ emissions are reduced by up to 9%; however, methane (CH₄) emissions due to incomplete combustion lead to CO₂e emissions that are 50–127% higher than the equivalent diesel vehicle. Oxidation catalysts evaluated on the vehicles at steady state reduced CH₄ emissions by at most 15% at exhaust gas temperatures representative of transient conditions. This study highlights that control of CH₄ emissions and improved control of in-cylinder CH₄ combustion are required to reduce total GHG emissions of dual fuel HGVs relative to diesel vehicles.