The desire and need to reduce environmental problems such as: environmental pollution, accumulation of garbage, exploitation of oil derivatives, excessive release of CO2, plastic in the seas and on land, were the reason for the preparation of new materials, which will have improved properties compared to individual components of which they consist of. The aim is to develop composites with a bio-base, preferably biodegradable, which would replace or at least partially replace already existing traditional materials. Polyethylene is one of the most well-known petroleum-based polymers, by mixing in eggshells, its mechanical properties could be improved. Various forms of this polymer are known with a wide range of applications. Samples of pure LLDPE, eggshell and LLDPE/LJJ biocomposite samples were examined by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) techniques. Using the DSC technique, it was determined that during the heating cycle, the addition of LJJ does not cause significant changes within the crystalline phase of LLDPE, that is, it does not affect the size of the crystals and their arrangement. After the 2nd cooling cycle, an exotherm was obtained, which represents the crystallization of the molten crystals in the heating cycle. The crystallinity (Tc) of the composite changes slightly with the increase in the proportion of LJJ. Infrared spectrum with characteristic bands of functional groups for individual samples was obtained by FTIR analysis. The analysis of individual bands of the samples shows that no absorption bands of characteristic wave numbers were obtained that would indicate the existence of LJJ, i.e. calcium carbonate within the composite.