Comparative Analysis of Fuel Consumption and Exhaust Emission Characteristics of Petrol and Compressed Natural Gas in Commercial Tricycles in Port Harcourt

The proliferation of tricycles as a primary mode of urban transport in South South Nigerian cities has intensified concerns about localised air pollution attributable to petrol combustion in unregulated two-stroke and four-stroke engines. This study presents a comparative analysis of fuel consumption rates and exhaust emission characteristics of tricycles operating on petrol and compressed natural gas in Port Harcourt, Rivers State. A fleet of ten tricycles, five running on petrol and five converted to CNG operation, was selected from the Rumuola and Mile 1 transport hubs. Fuel consumption was measured using a standardised driving cycle over a 10-kilometre test route, and exhaust emissions of carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter were measured using a portable exhaust gas analyser. Statistical comparisons were performed using independent samples t-tests. Results indicated that CNG-operated tricycles consumed approximately 18 percent less energy per kilometre on a cost-adjusted basis and produced 67 percent lower carbon monoxide and 54 percent lower hydrocarbon emissions compared to petrol counterparts. Nitrogen oxide emissions showed no statistically significant difference between fuel types. The findings support the case for incentivised CNG conversion programmes as a cost-effective urban air quality intervention in major South South cities. Keywords: compressed natural gas, petrol, exhaust emissions, tricycles, Port Harcourt.