ABSTRACT In this study, nutritious and abundant waste generated by sardine canneries was used as the main substrate to assess the effect of fundamental parameters in anaerobic digestion. The temperature range studied, between 37°C and 45°C, allowed for a comparison between the performance of the thermophilic and mesophilic processes. The free water content in the substrate also enabled us to compare fermentation in solid-state fermentation (SSF) with its counterpart, liquid-state fermentation (LSF). The study parameters also included the integration of Aspergillus niger (AN) and molasses. The results revealed significant effects of the AN inoculum and thermophilic conditions in improving biogas production. Optimal biotransformation generated a safe digestate that complies with French standards for use as a biofertilizer. Germination tests demonstrated that it has no inhibitory effect on tomato seeds and has the potential to enhance crop yields better than chemical fertilisers.