Over-exploitation of fossil resources of nature and increasing pollution have created the problem of finding alternative energy technologies, the invention of new equipments, based on highly efficient thermodynamic cycles, the use of new types of combustible material, i.e. the creation of environment-friendly energy systems, that will satisfy manufacturers and consumers’ demands, while minimizing the costs of material resources. Nowadays, there are well known mineral resources (coal, oil, natural gas, etc.), which are used universally. However, Russia has a huge potential for the application of non-traditional (alternative) energy sources on the basis of bio-waste usage. For example, in the construction of livestock farms, despite of their high equipment of mechanization and automation means, the questions of manure utilization remain unresolved. It should be noted that, a huge problem of recycling and rational application of liquid manure mass was formed. The cheap fuel production from agricultural waste for heating, electricity production and reception of high-quality organic fertilizers are the solution to the problem of utilization of large masses of liquid manure, ensuring protection of the environment from agricultural waste pollution. This article discusses the design and calculation of heat balance of compact biogas plant. The results of experimental studies of small-sized biogas plant at mesophilic and thermophilic fermentation time are also shown.