The use of hydrogen-containing fuel in gas turbines and industrial burners can benefit both losses of radiative heat and emission of pollutants. In this study, worthless waste hydrogen-rich fuel gas (RG) was led into a high-pressure boiler or a medium-pressure boiler in the fuel system to partially replace fuel oil (FO) and/or natural gas (NG) in a full-scale petrochemistry plant. Two sets of inlet fuel flow rate ratios were examined to evaluate the reductions of boiler energy consumption and CO2 emission. The result showed that for the high-pressure boiler at a loading of 75%, the usage of NG can be 13 x 10(6) m(3)/y less and the CO2 emission can be 2.2 x 10(4) tons/y lower by changing the inlet FO:NG:RG ratio from 1:1:0 to 1:0.65:0.35. Meanwhile, for the medium-pressure boiler at a loading of 70%, the usage of NG can be cut by 8 x 10(6) m(3)/y and the CO2 emission can be 3.0 x 10(4) tons/y lower by changing the inlet FO:RG ratio from 1:0.2 to 1:0.7. Therefore, the addition of RG has practical benefits on both energy saving and the reduction of greenhouse gas emission.