Influences of Feedstock Proportion and pH Value on Anaerobic Co-digestion of Kitchen Waste and Waste Paper

Using kitchen waste and waste paper as anaerobic co-digestion material, the influences of feedstock proportion(ratio of kitchen waste to waste paper at 100:0, 83:17 and 62:38, calculated by volatile solid) and pH value adjustment(6.5, 7.2 and 7.9) in the acidification stage on anaerobic digestion stability and performance was investigated.Experimental results showed that the proportion of 100:0 can not realize stable methane production due to the inhibition of volatile fatty acids.For the proportion of 83:17, methane yields were 313, 346 and 360 mL/g VS for three digestions with adjusting pH value at 6.5, 7.2 and 7.9 in the acidification stage.Methane contents of three digestions were 70%～80%.COD reductions were 86.3%, 93.2% and 95.2%.For the proportion of 62:38, methane yields were 97, 247 and 279 mL/g VS respectively, methane contents were 70%～80% for pH adjustment at 7.2 and 7.9(60%～70% for pH adjustment at 6.5), COD reductions were 32.6%, 80.5% and 86.8%.Compared with pure kitchen waste, the anaerobic co-digestion of kitchen waste and waste paper could avoid the inhibition of volatile fatty acids and improve good performance of digestions.