To investigate LSS an EXCEL Spreadsheet is designed. The spreadsheet consists of data on two different LSS types: biological and physico-chemical. Biological LSS include those based on hydrogen-oxidizing bacteria, microalgae, higher plants, higher plants and mushrooms, and higher plants with physical/chemical incineration of wastes. Simulations using this spreadsheet, showed that LSS with higher plants realize different structure of LSS (ratio of biological species, their mass, etc.) with different operation time. Thus, the system with higher plants has been found to have three different structures if incineration is used and six structures in opposite case. In the case of a vegetarian diet, 100% closure can be obtained.