Traditional composite materials used for construction purposes currently face many questions regarding their sustainability –mainly because they do not come from renewable sources and due to the problems related to their end-of-life management. These challenges motivate companies and researchers to look at the natural fiber composite materials with increased interest. Usually natural fiber materials in construction are used together with mineral binders, but in this research new organic binder –sapropel (organic rich lake sediments) is used as a binder for natural fiber composite materials with various fillers. In previous research these composite materials have proven their applicability in construction industry due to their sufficient mechanical strengthand low thermal conductivity. Thus, in this research evaluation of the biodegradability of composite materials were done, comparing them to natural fiber materials with mineral binders. As a methods respiration intensity of microorganisms in soil and enzyme activity of microorganisms were used. For studied materials biodegradability potential have been examined, depending on the filler propertiesand presenceof mineral matter content in the obtained compositematerials.