Volatile fatty acid production during anaerobic mesophilic digestion of solid potato waste

The production of volatile fatty acids by anaerobic digestion of solid potato waste was investigated using a batch solid waste reactor with a working capacity of 2 dm(-3) at 37degreesC. Solid potato waste was packed into the digester and the organic content of the waste was released by microbial activity by circulating water over the bed, using batch loads of 500g or 1000 g potato waste. The sequence of appearance of the volatile fatty acids was (acetic, propionic); (n-butyric); (n-valeric, iso-valeric, caproic); (iso-butyric). After 300 h digestion of potato waste on a small scale, the fermentation products were chiefly (mg g(-1) total VFAs): acetic acid (420), butyric acid (310), propionic acid (140) and caproic acid (90), with insignificant amounts of iso-butyric acid, n-valeric and iso-valeric acids. When the load of potato solids was increased, the volatile fatty acid content was similar, but butyric acid constituted 110 mg g(-1) and lactic acid 400 mg g(-1) of the total volatile fatty acids. The maximum soluble chemical oxygen demand (COD) achieved under the experimental conditions used was 27 and 37 g COD dm(-3) at low and high loadings of potato solids, respectively. The total volatile fatty acids reached 19 g dm(-3) of leachate at both loads of potato solid waste. Gas production was negligible, indicating that methanogenic activity was effectively inhibited. (C) 2004 Society of Chemical Industry.