The valorisation of biowaste in the fabrication of carbon quantum dots (CQDs) as a sustainable value-added carbon nanomaterial can contribute to the integration of circular bioeconomy concepts in the existing economic systems. Herein, this study evaluated the cradle-to-gate environmental life cycle assessment of carbon quantum dots from biomass waste (rubber seed shells). The approach of utilising biowastes coupled with microwave-assisted method has the potential towards a more cost-effective and sustainable CQDs production. The results of life cycle impact assessment (LCA) using the ReCiPe method and SimaPro 8.5 software for 1 g of CQDs and the highest contributions to the environment over all the processes in the midpoint approach are global warming potential with 18.22 kg CO2 eq, land use with 13.71 m2a crop eq and human non-carcinogenic toxicity with 12.49 kg 1, 4-DCB characterisation values. The total characterisation factors of the endpoint categories for human health are 5.08E-05 DALY, 1.96E-07 species per year for the ecosystem and 1.01 USD2013 for resource availability. Sensitivity analysis using different sources of energy was assessed and revealed that the impacts descending in severity: Grid > Grid/Natural gas > Grid/PV, while using different types of chemicals revealed that using ammonia as the precursor in the activation of CQDs is better than urea and citric acid. Future research should start considering valorising biomass waste and upscaling it into a value-added carbon nanomaterial. This study can aid decision-makers and management strategy that is environmentally sustainable for the application of nanomaterials.