This study was performed to investigate the anaerobic digestion feasibility of kitchen waste and blackwater under different scenarios in laboratory tests. According to biochemical methane potential tests, when the kitchen waste to blackwater solid ratio was 1:1, the cumulative methane production reached the highest amount at 313.2 mL/g volatile solids (VSs), which was 26.4% and 29.4% higher than the anaerobic monodigestion of kitchen waste and blackwater, respectively, indicating that the anaerobic codigestion of kitchen waste and blackwater had a synergetic effect. Furthermore, the effect of different initial total ammonia nitrogen concentrations in blackwater on anaerobic digestion was determined based on the above experimental results, thereby proving that reducing the total ammonia nitrogen concentration in blackwater can appropriately improve the efficiency of methane production. Therefore, anaerobic digestion is a suitable method for the biogas production of kitchen waste and blackwater. It is of great significance for the organic waste stream treatment of households in a decentralized scale, especially in rural areas.

Anaerobic digestion (AD) has been widely adapted for blackwater treatment, however, the effect of water-conserving toilet generated blackwater on the AD process is still unknown. In this study, the anaerobic digestion process of dry toilet generated blackwater was investigated by means of a biomethane potential test. It was demonstrated that anaerobic digestion was inhibited and then adapted because of a high total ammonium nitrogen (TAN) level (3673.3 mg/L). The start-up period was 14.04 days and the biomethane potential of dry toilet blackwater was 402.36 mLCH₄/gVS (55 days, 38 °C). Inhabitation and adaptation could be described as the increase of free ammonia nitrogen content and acetic acid concentration, followed by an enhancement of the relative abundance of acetic acid-type methanogens (from 33.53–61.52%). The main pathogen in dry toilet blackwater fermentation broth, Pseudomonas aeruginosa, kept multiplying in the first 8 days and then stabilized at a higher level than that of the beginning. This work showed the self-adjustment process and pathogen dynamics of dry toilet blackwater anaerobic digestion and highlights the significance of dry toilet blackwater characteristics when designing and maintaining anaerobic digestion sanitary treatment and reuse systems.