Valorization of spent coffee grounds: techno-economic and environmental assessment of a multi-product biorefinery

Spent coffee grounds are an abundant agro-industrial residue with significant potential for valorization within circular bioeconomy frameworks. This study proposes an integrated hydrothermal carbonization-based biorefinery for the simultaneous recovery of products targeting renewable energy, nutraceutical and agricultural applications. HTC is used as a platform process enabling the generation of a liquid and a solid carbon-rich fraction, which are subsequently upgraded into value-added products. Four process configurations were systematically evaluated, including a baseline scenario integrating oil recovery, prebiotics, iron-functionalized melanoidins and iron-functionalized hydrochar, and three alternative scenarios derived by progressive removal of selected unit operations to assess the impact of process simplification on economic and environmental performance. The baseline configuration proved economically viable at a processing capacity of 10t/batch (1.4 kt/year), achieving an NPV of 108.2 M$, an IRR of 18.53% and a payback period of 3.98 years under average market prices, while Scenario 2 exhibited the highest techno-economic performance, increasing the NPV by 463%. From an environmental perspective, simplified configurations that excluded solvent-intensive stages showed the lowest impacts across all categories, with the production of Prebiotics and iron-functionalized hydrochar in scenario 3 and iron-functionalized melanoidins in scenario 1 being the most environmentally favorable. Overall, the results underline the potential of SCG biorefineries to achieve economic viability and resource circularity through integrated multiproduct strategies, while indicating that further reductions in energy (steam comsuption) and water consumption are essential to fully validate their industrial scalability and environmental sustainability.