Four pretreatment methods, including alkaline, chlorine dioxide, ultrasound, and homogenization, were screened for sludge disintegration to selectively release carbon from surplus activated sludge (SAS), while avoiding nutrient (phosphorus and nitrogen) release. The characteristics of these methods in terms of carbon, nitrogen, and phosphorus releases were compared, and the variation between the actual and theoretical values of those releases was evaluated. The results showed that the four pretreatment methods had different preferences in both carbon and nutrient release, indicating a possibility of selective release. Ultrasound had a preference in carbon release while not in nutrient release, and was a good method for selective release of carbon source. But homogenization was chosen for sludge disintegration to obtain carbon source from SAS with a cost consideration. And alkaline and chlorine dioxide pretreatment methods were not advocated for a low selective release of carbon source and a gas emission into environment. (C) 2014 Elsevier B.V. All rights reserved.