Pyrolysis of difficult biodegradable fractions and the real syngas bio-methanation performance

Abstract

Sustainable approaches for the anaerobic digestion treatment of food waste to minimize environmental challenges and recover energy are some economic goals receiving global attention. Meeting global bio-energy demand from food waste and associated waste residues requires exploring alternative optimization routes. Pyrolysis process for the treatment and recycling of difficult biodegradable fractions in food waste processing facility, and the subsequent utilization of real syngas in anaerobic digestion as a food waste treatment were investigated to evaluate their effects on biofuel production via bio-methanation. Different proportions of syngas that are transformed into methane show that the carbon monoxide content in the reactors (G21, G23, G61, and G63) was completely degraded on 195, 195, 95, and 145 h. The higher hydrogen concentration in the simulated syngas expedites the carbon monoxide degradation rate. Application of two-stage pyrolysis to difficult biodegradable fractions treatment generated real syngas (Hydrogen 60: Carbon monoxide 20 vol%) for improved bio-methanation (100% methane) compared to the blank. The simulated syngas from the anaerobic digestion treatment of food waste generated methane (75–80%) than the control (45%). Results from both the simulated and real syngas show that high volume percent of hydrogen in the syngas positively influenced the degradation and transformation of carbon monoxide and promoted a higher rate of bio-methanation. Further study showed that pH values in the range 7.21–7.78, and low concentrations of volatile fatty acids and ammonia nitrogen indicated no toxicity from syngas bio-methanation with anaerobic digestion. This route is beneficial for enhancing the value of resources recovered from difficult biodegradable fractions pyrolysis, achieving a higher bio-methanation rate, and improving sludge stabilization with anaerobic digestion treatment of food waste.