Despite the improved thermal stability and mechanical properties of polymer-clay nanocomposites compared to pure polymeric materials, creating nano composites with enhanced thermomechanical properties requires a good compatibility and dispersion of the clay within the polymeric matrix. This paper introduces a bioresidue extracted from waste biomass to modify montmorillonite clay to compatibilize it with linear low density polyethylene (LLDPE). The biomodified day was compounded, melt blended, and injection molded with LLDPE, and the thermomechanical properties of the resulting nanocomposites were investigated with oscillatory rheometry, thermogravimetric analysis, X-ray diffraction, attenuated total reflectance Fourier transform infrared spectroscopy, and transmission electron microscopy to assess the compatibility of the biomodified day and the polymer. The structure of the biomodified clay ranged from partially intercalated to fully exfoliated. Hansen solubility parameters indicate that almost all of the identified compounds in the bioresidue are soluble with polyethylene. Density Functional-based modeling showed a trade-off between electrostatic screening and dispersion interactions affecting the overall interlayer spacing in polymer-clay nanocomposites.