The research carried out in this work determined the biochemical methane potential of the solid fraction remaining after acid fermentation with the recovery of volatile fatty acids and hydrogen, in which kitchen waste was used as the substrate. The methane fermentation process was carried out in bath bioreactors without pH regulation during the process, with the addition of digestate sludge from wastewater treatment plants and without its addition, at various substrate concentrations. It was found that the solid fraction after acid fermentation with the addition of digested sludge, is a good substrate for biogas production. The highest biochemical methane potential of 640 cm³ CH ×gsmo^-1 was found in the process in which the waste solid fraction after acid fermentation concentration was 100 gm×dm^-3.

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