Experimental investigation on the potential of biogas/ethanol dual-fuel spark-ignition engine for power generation: Combustion, performance and pollutant emission analysis

•Biogas/ethanol dual-fuel improved combustion phasing.•Dual-fuel inhibited knock occurrence at full load condition.•Combustion efficiency was enhanced due to the lower HC and CO pollutant emission.•NOx reductions of up to 30% were achieved compared to pure ethanol operation.•Fuel conversion efficiency increased when dual mode was used. Dual-fuel mode in internal combustion engines has been proved as a potential technique for either achieving near-zero pollutant emissions through fuel reactivity modifications or reducing carbon dioxide (CO2) emissions by partially replacing a fossil fuel by a renewable one. This manuscript presents an experimental study of a dual-fuel engine fueled with two biofuels, biogas and bioethanol, for two liquid fuel replacements of 20 and 50% by energy. Tests were performed in a spark-ignition single-cylinder engine with a modified compression ratio, under different engine speeds (1800 and 3600 rpm) and loads (4 bar of IMEP and full load condition). Results show that dual-fuel mode accelerated the combustion rate when compared to biogas single-fuel operation and increased combustion completeness, leading to reduced carbon monoxide (CO) and unburnt hydrocarbon (HC) pollutant emissions, thus, improving combustion efficiency. At full load conditions, dual-fuel mode suppressed knock occurrence and raised the load limit for 20% biogas energy fraction when compared to ethanol single-fuel condition. Moreover, nitrogen oxides (NOx) emissions were decreased in dual-fuel mode (comparing to ethanol) and fuel conversion efficiencies enhanced considerably. The innovative approach of combining two promising renewable fuels proved to be a very effective methodology in reducing exhaust pollutant emissions and increase engine overall efficiency.