Table 3 The differentiation between conventional pyrolysis and microwave pyrolysis

Heating mode

Conventional heat source heating

Microwave heating

[7, 8]

Energy conversion

Chemical energy, electrical energy, etc., into heat energy

Electromagnetic energy into heat energy

[10]

Heating path

Superficial heating via conduction, convection, and radiation

In-core volumetric and uniform heating at molecular level

[8]

Heating characteristics

Nonuniformity, tardy

Selectivity, immediacy, uniformity, high efficiency

[9, 19, 27]

Pyrolysis process

Slower, longer time

Faster, shorter time

[8, 16]

Main influencing factors

Pyrolysis temperature, heating rate, catalyst

Pyrolysis temperature, heating rate, microwave absorbers, sludge properties

[12, 21, 23, 24]

Pyrolytic products

Pyrolysis residues, pyrolysis oil, pyrolysis gas

Pyrolysis residues, pyrolysis oil, pyrolysis gas, the quality of pyrolysis oil/gas is better

[26]

Harmful products

Relatively more, strong carcinogenic character

Relatively few, little carcinogenic character

[32, 39, 41,42,43]

Energy output rate

Relatively low utilization rate

Relatively high utilization rate

[37]