Acid inhibition during anaerobic digestion of biodegradable kitchen waste

The aim of this work was to investigate the acid inhibition during the anaerobic digestion of kitchen waste. Four biodegradable substrates of soybean, fat meat, rice, and celery cane were considered in this paper. A series of anaerobic codigestion tests were performed on the four substrates at the load of 1.0 gVS/(l.day) and anaerobic granular sludge. The results show that the acid inhibition was occurred at the load of 1.0 gVS/(l.day) for the soybean and rice; the corresponding pH values at the lowest acidification points were 5.03 and 3.73, respectively. There was no acid inhibition during the whole digestion period for the celery cane substrate. And the results also reveal that the order of the cumulative gas yields for different substrates from highest to lowest is: celery cane > soybean > fat meat > rice; while the order of the average methane (CH4) percentage from highest to lowest is: celery cane > fat meat > soybean > rice. Finally, the method to calculate the lowest acidification points of the four substrates was provided by the least squares method, and it is verified by the measured data, and good agreement is found. (C) 2015 AIP Publishing LLC.