A considerable portion of the populations living in the rural areas of developing countries mostly solely rely on traditional biomass for cooking, lighting and heating purposes. The prime concerns with such conventional energy dependency include deforestation, environmental degradation, ecological imbalance, sanitation and other public health issues and socioeconomic difficulties. Therefore, implementing small-scale biogas plants at household level could be accompanied with positive and synergistic effects in mitigating such integrated global problems. Moreover, promoting and executing small-scale biogas technology in both rural and urban areas, using generally freely available local organic resources, could result in more sustainable national energy demands and reduce the use of traditional biomass and imported fossil fuels. Doing so, the targets of renewable energy generation, mitigation of GHGs emissions and sustainable waste management could be fulfilled. In this chapter, different small-scale biogas plants including their history, designs, operation, etc. are presented and discussed.