Biodigesters can be a suitable solution to exploit organic waste, fermenting it into biogas and biofertilizer. The presented type of biodigesters is easy to build, to operate, and to maintain even by nonqualified personal. In this document, guidelines for the design, as well as for the installation and for the operation of a small biodigester in rural areas is presented. The most important components and their function in the process of organic digestion are also described. The calculation is simplified to an iterative process to determine the geomembrane dimensions for a given daily organic waste production.