Short-term sludge fermentation was explored as a means of solubilizing phosphorus from different types of undigested sludge to facilitate nutrient recovery and generate volatile fatty acids (VFA) for enhanced nutrient removal. Phosphorus solubilization and VFA production was compared from the fermentation of primary sludge (PS), waste activated sludge (WAS), and from co-fermenting primary and waste activated sludge from wastewater treatment plants that do not practice biological nutrient removal. Co-fermented sludge resulted in the best combination of nutrient release and VFA production compared to separate fermentation of PS and WAS. After 4 days of fermentation, co-fermented sludge contained 48% of TP as dissolved phosphorus, and produced 1624 mg l-1 of VFA-COD which corresponds to a VFA-COD production rate of 0.139 mg mg-1 VS. In terms of total sludge management, co-fermentation resulted in greater overall VFA production and phosphorus solubilization than individual sludge fermentation.