Biogas is a promising renewable energy source having great potential, especially in livestock farms. However, as biogas electric generators are usually deployed in rural areas, it would take more time and effort to repair if any fault occurs. Remote monitoring of the system condition is essential to diagnose or even predict the faults in advance and subsequently plan the maintenance schedule in time. This paper presents a monitoring system of biogas-based power generation system using Internet-of-Things (IoT) devices. Information of the generator operation is acquired by field devices and forwarded to a remote server. Data collection and management are facilitated by Lambda architecture and Apache Kafka software platform for their interoperability and strong support of big data management. The system shows that near real-time supervision of the object conditions can be obtained. Historical data analyses of a few operation scenarios are also provided to evaluate the generation system performance as well as to discuss its fault diagnosis.