Biogas is a renewable gaseous fuel with potential to replace traditional fossil fuels in spark-ignition (SI) engines, particularly for small-scale power generation. Its typical volumetric composition consists of 60% methane (CH4) and 40% carbon dioxide (CO2). The high amount of CO2 in biogas significantly degrades the engine characteristics with high cycle-to-cycle variations (CCVs) of combustion particularly at low and intermediate loads. Utilization of green hydrogen for reduction of CCVs is particularly attractive for biogas fueled SI engines. Therefore, in the present work, hydrogen (a highly reactive and renewable fuel with wide flammability limit, low minimum ignition energy requirement and high flame speed) was blended with biogas in different proportions i.e. 5, 10, 20, and 30% (by volume). A gas blending setup for evaluating engine characteristics was developed for blending three gases with compatibility of incorporating highly reactive fuels like hydrogen. A single cylinder SI engine was operated at compression ratio of 10:1 and engine speed of 1500 rpm for stationary application purposes. First, a comparative study of engine characteristics was performed with fuels i.e. gasoline, biogas and methane. Later experiments were conducted to investigate the effects of hydrogen addition in biogas on engine performance, emissions and combustion with enhancement of low operating load at stoichiometric condition. The CCVs of combustion were studied using statistical and wavelet based approaches. A CFD model of the used engine configuration was also developed and validated with the measured data using CONVERGE CFD for improved understanding of the combustion process. The comparative experimental study showed high CCVs in the case of gasoline compared to biogas and (least for) methane. Results with hydrogen addition showed an increase in brake thermal efficiency by 5, 9.8 and 7.2% for 10, 20 and 30% of hydrogen addition respectively. The maximum rate of in-cylinder pressure rise increased with hydrogen addition in biogas and revealed shorter flame initiation and combustion durations. Wavelet analysis results showed that strong intensity short lived high frequency bands were completely vanished with hydrogen addition, hence decreased CCVs. CFD results showed an increase in concentrations of H, O and OH radicals with hydrogen addition in the fuel mixture which ultimately accelerated flame propagation. Overall, lower operating load enhanced from 6 N-m (from the case of biogas) to 5.3, 2.2, 1.5 and 0.8 N-m (close to the no load condition) for 5, 10, 20 and 30% of hydrogen addition in fuel mixture, respectively. Emissions of hydrocarbon, carbon monoxide and carbon dioxide decreased, whereas oxides of nitrogen were increased however were well below (by half) when compared to the case with pure methane.