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To address the problem of heating biogas project and compensating the lost ground temperature of ground source heat pump system, the integrated solar and ground source heat pump system (ISGSHPS) was presented for heating biogas digester, and the economic and environmental performance of ISGSHPS with that of ground source heat pump and electricity heat membrane system were compared to obtain the optimal solar collector area. The results show that the optimal solar collector area is related to annual total running hours and electricity price. The most economic running period is from October to the next May; ground source heat pump system is more economical than ISGSHPS when electricity price is lower than 0.5 Yuan per kW·h; when the electricity price is between 0.5 and 1.0 Yuan per kW·h or higher than 1.0 Yuan per kW·h, the optimal solar collector area of ISGSHPS is 24m2 and 32m2 respectively. At present, the optimum collector area is 24m2, under which total cost saving in 20 years is 10830 Yuan and 59244 Yuan, and carbon dioxide emissions could be reduced about 74t and 266t by comparison ISGSHPS with ground source heat pump and electricity heat membrane system. Therefore, this system has potential to develop.