Solid Pellet Biofuel Made from Coffee Grounds: Experimental and Environmental Analysis

Spent coffee grounds (SCGs) are a waste product generated in large volumes worldwide, given that coffee is the second most consumed beverage on the planet. Although it typically ends up in landfills, this biomass contains a high amount of nutrients, organic compounds, and other physical properties that can be harnessed. It is possible to recover energy from coffee grounds through pellet production because this biomass has a calorific value ranging from 19.6 to 21.1 MJ/kg—values comparable to, and even higher than, those of traditional fuel biomasses, such as pine sawdust (18.64 MJ/kg) or eucalyptus wood (17.38 MJ/kg). To produce the pellets, different formulations were prepared by incorporating up to 25% SCGs and up to 80% recycled woody material, depending on the specific formulation, followed by the addition of the 5% additive. All proportions were expressed as percentages of the total biomass mixture mass. The resulting pellets were characterized in accordance with ISO 17225-1 and have been classified as Type B non-woody pellets. Given that bioenergy derived from waste plays a fundamental role in climate change mitigation and the circular economy, a cradle-to-gate life cycle assessment was conducted using the ReCiPe 2016 Endpoint method. The results revealed that the pellets containing SCGs were more environmentally friendly.