Assessing the Potential of CBG as an Alternative Fuel: An Experimental Study on Vehicle Performance and Emissions in BS VI Compliant Three-Wheeler and Passenger Car

India's natural gas consumption reached 60.3 billion cubic meters (BCM) in the year 2022-23, with imports accounting for 44.2% of the total consumption. As India targets 15% of primary energy consumption from gas by 2030, the demand for natural gas is expected to grow significantly. In this context, CBG, which can reduce dependence on imported natural gas, has emerged as a viable alternative to CNG. The government's SATAT (Sustainable Alternative Towards Affordable Transportation) initiative encourages entrepreneurs to establish CBG plants and supply CBG to Oil Marketing Companies (OMCs) for use as automotive and industrial fuels. As of April 2023, 47 CBG plants have been set up, and 117 retail outlets in India are selling CBG as a transportation fuel. The quality requirements of CBG are governed by IS 16087, aligning with the specifications for automotive CNG defined in IS 15958. To assess the impact of CBG on vehicle performance and emissions, an experimental study was conducted using unmodified BS VI three-wheeler and passenger car CNG vehicles. Commercial CNG served as the baseline fuel, while a commercial CBG sample was used as the candidate fuel. The experiments followed the Indian driving cycle (IDC) and modified Indian driving cycle (MIDC) test cycles for three-wheelers and passenger cars, respectively. The results obtained from the commercial CBG fuel demonstrated comparable levels of carbon monoxide (CO) and total hydrocarbon (THC) emissions for CNG and CBG fuels. Notably, CBG led to a reduction of 14.6% in NOx emissions for three-wheelers and 9.4% for passenger cars, while non-methane hydrocarbon (NMHC) emissions decreased by 35.6%. Further, the fuel economy of the test vehicles was found to be comparable for CNG and CBG fuels. These findings highlight the emission reduction potential of CBG fuel, particularly NOx and NMHC, while maintaining fuel economy, indicating its viability as a sustainable alternative.