Gaseous fuels from alternative or renewable sources can be produced by different manners. However, the main disadvantage of these gases is their fluctuating composition and properties in comparison with the natural gas. Nevertheless there is a posibility to use the existing natural gas grid for transport and distibution of these gases. But these gases have to fulfill several conditions. The main technical and legislative obstracles for utilization of gases from thermal and fermentation processes in the Czech Republic are given in this paper.