This study comprehensively compares the anaerobic digestion followed by incineration (ADI), and incineration without digestion (INC) routes based on energy balance, material flows, environmental impacts, emergy analysis (EA), and investment and operational (I&O) from life-cycle perspective. Traditional anaerobic digestion (AD) exhibits low AD efficiency and volatile solid (VS) content, and INC outperforms ADI in terms of environmental impacts and economic performance, whereas the ADI shows greater sustainability potential. With high total solids (TS), the AD energy consumption decreases significantly, and the energy gap between ADI and INC routes is expected to be eliminated at TS content of 7%. Furthermore, the higher AD efficiency tends to produce more biogas and decreases energy consumption and operational costs of thermal drying. According to the I&O and EA results, sludge with higher VS, that is, above 60%, exhibits better ecological and economic benefits, even though 65% extra capital investment is required for biogas equipment.