Table 3 Summary of previous research works on BC-amended reactors and the subsequent influence of BC on AD performance and the enhanced microbial population

Fruitwoods (800 °C)

BC levels (2, 4, 6, and 8 g/l); and BC sizes (2–5 mm, 0.5–1 mm, and 75–150 μm)

• CH₄ decreased at increased glucose due to the increase in soluble microbial products at higher stress levels

• Smaller particles are better in VFA degradation

• Methanobacterium was most enriched followed by Methanosaeta and Methanosarcina

• Syntrophomonas increased to 29.2% followed by Clostridiaceae

[126]

Fruitwoods (800–900 °C)

Total ammonium concentration of 3.5 g-N/L

• λ = 12.7%; R_max = 10.1%; VFA = 66 mmol-C l⁻¹

• Inoculum was highly populated by Proteobacteria and Firmicutes

• Enterobacteriaceae was detected at the end of AD

• Clostridium and Porphyromonadaceae were enriched at the later stage

• Methanobacterium increased from 30%(inoculum) to 92.1% (early stage) to 65.6% (final stage)

• Methanosaeta and Methanosarcina were suppressed

[50]

Fruitwoods (800–900 °C)

Total ammonium concentration of 7.0 g-N/L

• λ = 23.8%; Rmax = 23.5%; VFAs = 66 mmol-C l⁻¹

• Enterobacteriaceae was detected at the early stage and was enriched to the final stage

• Methanogens and Methanosaeta were suppressed

[50]

Sawdust BC (650 °C) at 20 min retention time with fractional size 3.5–25.9 μm

BC addition ratios of 8.3, 16.6, 25.1, and 33.3 g-l⁻¹

• The CH₄ yields for 25.1 and 33.3 g-l⁻¹ BC were lower than the control (1070.0)

• CH4 decreased at an increased dosage of BC

• The highest CH₄ yield (1136.6 ml-l⁻¹) was observed at 8.3 g-l⁻¹

• Lower methane production was recorded from 33.3 g-l⁻¹

• Higher BC dosage had more propionic acid accumulated which led to low pH

• The addition of BC promoted biofilm formation

[102]

Canola meal (700 and 900 °C) and; switchgrass (500 °C); and Ashe juniper (400 and 600 °C)

Biomass types and temperature

• Effective reduction in lag time

• CH₄ improvement was 72% for SBC-500, and ABC-400 (71%), compared to GAC (40%) and PAC (24%)

• The COD reduction was 94% for GAC, whereas 93% for PAC, 94% for SBC-500, 93% for ABC-400, and GLU was 81%

• Lewinella was the most enriched archaea (18%, SBC-500), (16%, ABC-400), (19%, GAC), (18%, PAC), and (16%, Glucose) followed by Bacteroides, Bacillus, and Dechloromonas

• Methanogens like Methanothermobacter were most enriched at 76.2, 60.1, 64.1, 74.5, and 77.7% for ABC-400, SBC-500, GAC, PAC, and glucose, respectively, followed by Methanosarcina

[6]