Table 5. Advantages and Disadvantages of Different Gasifying Agents Used in the Gasification Process⁴¹.

gasification agents	advantage	disadvantage	gas component
air	cheap gas source, high economy, abundant resources, medium tar generation	with high N2 content and low H2 volume fraction, the product gas has a low calorific value, and the resulting gas is generally used as a raw material for chemical synthesis gas.	CO, CO2, H2, CH4, N2, tar
O2	medium calorific value gas, a small volume of gas, reduced sensible heat loss, improved efficiency, lowest tar content, high volume of combustible components	energy consumption for O2 preparation, high cost, and poor economy	CO, CO2, H2, CH4, tar
steam	high H2 preparation, high and medium calorific value gas generation, and good gas quality all allow for direct fuel usage	additional equipment is required, increasing system complexity and cost and reducing equipment independence	CO, CO2, H2, CH4, tar
air–steam	combining the advantages of water vapor and air vaporization, the economy is obvious	relatively complex system	CO, CO2, H2, CH4, tar
H2	the high calorific value of combustible gases	high reaction conditions, not currently applied, still under research	CO, CO2, H2, CH4, tar