Review: Determining Factors in the Pelletization of Coffee Grounds as Solid Biofuel

The growing demand for pellets as a renewable energy source reflects the global need to reduce dependence on fossil fuels and promote more sustainable production models. Despite recent challenges, such as rising production costs and raw materials shortages, the pellet industry has maintained steady growth, highlighting the role of the circular economy in resource optimization and waste reduction. In this context, the exploration of new biomass sources for pellet production is presented as a key strategy, including agricultural, forestry and agri-food waste. Coffee, the second most consumed beverage worldwide, generates large volumes of organic waste, whose inadequate management represents a significant environmental problem. In particular, spent coffee grounds (SCG) have a high moisture content ( \(\sim\) 70%) and organic compounds, which facilitates the generation of pollutant emissions and increases the risk of spontaneous combustion, underscoring the need for valorization strategies. The main objective of this research is to evaluate the potential of SCG as a raw material for pellet production by analyzing its physicochemical properties, its behavior during the pelletization process and its classification according to ISO 17225–6:2021 standards for non-woody pellets. Integrating these residues into solid biofuel production, along with optimizing densification parameters, could provide an innovative and viable alternative aligned with the principles of the circular economy, contributing to waste reduction and the development of more sustainable energy sources.