The treatment of waste sludge generated from on-site wastewater treatment facilities (Johkasou) applied extensively in Japan is a key concern. In this study, a high-solid anaerobic membrane bioreactor (AnMBR) was continuously operated throughout a year to investigate the bioenergy production, material flow and seasonal impacts of concentrated Johkasou sludge (CJoS). The CJoS has higher carbon-to-nitrogen ratio and lipid fraction, but less proteins than waste activated sludge (WAS). The biogas yield of CJoS by AnMBR ranged from 0.47 to 0.52 L/g-VSfed, which was higher than the anaerobic digestion of WAS and lower than mixed sewage sludge from centralized wastewater treatment facilities. The greatest biogas production rate was observed during summer (0.63 L/L/d), owing to the high total organic and solid content. However, winter CJoS had the highest biogas yield and carbon conversion rate owing to the conservation of soluble organic matter in low temperature and high digestibility. The material flow results revealed that 46.5–52.4% total COD and 50.2–58.0% carbon was converted to biogas. The energy recovery rates ranged from 8.69 to 9.96 kJ/g-VSfed and the system energy self-sufficiency rates ranged from 1.92 to 3.02. The optimal dewaterability of digested sludge was achieved when polyamidine flocculant dosage was 30 mg/g-MLSS and the corresponding sludge specific resistance to filtration was 2.26 × 1012 m/kg. The results demonstrated that AnMBR yielded high energy conversion efficiency without co-digestion and pretreatment processing.