Bioenergy, produced through the anaerobic digestion (AD) of renewable organic feedstocks, is considered to be one of the highly promising alternatives to fossil-derived energy. The digestate residues obtained from AD finalized to bioenergy production have recently begun to be recognized as underutilized natural resources that have unrecognized value. This work is focused on the new added valorization of digestates obtained from the AD of organic substrates. Effect of digestates treatments and concentration on the properties of composites were investigated. The results obtained showed increase of mechanical and chemical resistance of composites by the heat treatment of digestates. Composite having 30% unsilanized calcined-digestate fillers was found to have the highest chemical and mechanical properties.