Enhanced methane production from the anaerobic co-digestion of food waste plus fruit and vegetable waste

Utilization strategy for algal bloom waste through co-digestion with kitchen waste: Comprehensive kinetic and metagenomic analysis

Anaerobic co-digestion (AcoD) with kitchen waste (KW) is an alternative utilization strategy for algal bloom waste (AW). However, the kinetic characteristic and metabolic pathway during this process need to be explored further. This study conducted a comprehensive kinetic and metagenomic analysis for AcoD of AW and KW. A maximum co-digestion performance index (CPI) of 1.13 was achieved under the 12% AW addition. Co-digestion improved the total volatile fatty acids generation and the organic matter transformation efficiency. Kinetic analysis showed that the Superimposed model fit optimally (R2Adj = 0.9988-0.9995). The improvement of the kinetic process by co-digestion was mainly reflected in the increase of the methane production from slowly biodegradable components. Co-digestion enriched the cellulolytic bacterium Clostridium and the hydrogenotrophic methanogenic archaea Methanobacterium. Furthermore, for metagenome analysis, the abundance of key genes concerned in cellulose and lipid hydrolysis, pyruvate and methane metabolism were both increased in co-digestion process. This study provided a feasible process for the utilization of AW produced seasonally and a deeper understanding of the AcoD synergistic mechanism from kinetic and metagenomic perspectives.

Review in anaerobic digestion of food waste

Due to the special property of food waste (FW), anaerobic digestion of food waste is facing many challenges like foaming, acidification, ammonia nitrogen and (NH4+-N) inhibition which resulted in a low biogas yield. A better understanding on the problems exiting in the FW anaerobic digestion would enhance the bio-energy recovery and increase the stable operation. Meanwhile, to overcome the bottle necks, pretreatment, co-digestion and additives is proposed as well as the solutions to improve biogas yield in FW digestion system. At last, future research directions regarding FW anaerobic digestion were proposed.

Anaerobic co-digestion of corn straw, sewage sludge and fresh leachate: Focusing on synergistic/antagonistic effects and microbial mechanisms

Effects of sewage sludge (SS) and fresh leachate (FL) addition on corn straw (CS) digestion and underlying mechanisms were investigated. Co-digestion of CS, SS and FL significantly increased cumulative methane production by 7.2-61.1%. Further analysis revealed that co-digestion acted mainly on slowly degradable substrates and exerted dual effects on methane production potential, which was closely related to the volatile solids (VS) content. Antagonistic effects of co-digestion resulted from the dominance of norank_c_Bathyarchaeia, a mixotrophic methanogen that may generate methane inefficiently and consume existing methane. The synergistic enhancement of methane production (0.7-12.7%) was achieved in co-digestion with 33.5-45.5% of total VS added as SS and FL. Co-digestion with more balanced nutrients and higher buffering capacity enriched Actinobacteriota, Firmicutes, and Synergistota, thereby facilitating the substrate degradation. Furthermore, the predominant acetoclastic methanogens, increased hydrogenotrophic methanogens, and decreased methylotrophic methanogens in the digester combined to prompt the synergy.