Unlocking the hidden carbon pool: Refractory organic matter drives superior chain elongation in sludge alkaline fermentation liquid - Dingkang Qian; Ziming Xu; Mengjiao Yuan; Zhen Li; Qian Zhu; Ming Peng; Jianyu Gong; Jiakuan Yang; Jingping Hu; Huijie Hou (Water Research, 2026)