A comparative life cycle assessment of different spent coffee ground reuse strategies and a sensitivity analysis for verifying the environmental convenience based on the location of sites

Spent Coffee Ground (SGC) represents the most abundant waste generated in coffee beverage preparation and instant coffee production, with a total annual amount estimated at 60 million tons worldwide. These quantities justify the need to enhance and reuse this waste, by implementing successful circular economy strategies. For this purpose, the production of compost, biofuels, and the incorporation of limited quantities of SCG in the bricks-making process represents a promising solution, which can avoid the impacts due to its disposal but also, result in lower greenhouse gas emissions. The present study aims to assess the environmental performance of different SCG reuse scenarios, compared to traditional landfill disposal. To evaluate environmental impacts, a comparative Life Cycle Assessment is performed among the aforementioned scenarios. The results showed that in terms of emissions to air, all the reuses investigated involve benefits compared to landfill, resulting in a decrease of 18% in composting, 1% in biodiesel production, and 76% in bricks-making. For this purpose, the success and real applicability of circular economy models are influenced by numerous factors, including distances and transport, which represent crucial elements in the evaluation of environmental benefits. Furthermore, a sensi-tivity analysis was implemented, to evaluate the maximum break-even distances within which the analyzed scenarios guarantee an environmental benefit, compared to landfill disposal. According to the obtained results and considering a distance of 100 km for the transport of SCG to the landfill, the calculated break-even distances are 500 km for composting, 150 km for biodiesel production, 1800 km for bricks-making; for longer distances, the additional impacts due to transport would cancel out the benefits deriving from the reuse of waste. Finally, the calculated break-even distances were compared with the average distances of the real sites in the Italian scenario, resulting in average distances for composting and brick production less than the break-even ones (40 km and 460 km respectively). On the other hand, the average distance among biodiesel production plants in Italy (500 km) is much higher than the calculated break-even one.