Pyrolysis and gasification represent a thermo-chemical process of solid mass conversion and the products obtained are: liquidity (pyrolytic oil), gases and coke residue. In modern society, there is a growing need for the use of ecological systems and renewable energy sources. As a potential and renewable energy resource we can consider sewage sludge. Sewage sludge is mostly disposed of in nature, while a very small part of the treats. Due to the non-adequate treatment of sewage sludge there is a high risk of impacts of harmful substances on humans and animals. Apart from the fact that the sewage sludge can be a major energy potential, thermal treatment allows to solve the problem of disposal of sewage sludge in nature and environmental pollution. Utilizing the sewage sludge as an energy source would generate large fossil fuels, neutralize sewage sludge landfills and reduce the risk of developing and spreading the disease due to the presence of harmful substances.