Future Prospects of Spent Coffee Ground Valorisation Using a Biorefinery Approach

Abstract

In the UK, half a million tonnes of spent coffee ground (SCG) waste are generated annually. Current SCG management practices of landfill and energy-from-waste (EfW) facilities either underutilise its valuable constituents or have negative environmental impacts. This study investigates the prospects of SCG-based biorefineries by assessing the impact of biorefinery size, location and products on economic and environmental performances. Two biorefinery design configurations are proposed. Configuration I produces biodiesel and electricity whilst Configuration II produces biodiesel and high-value chemicals. From these configurations, four biorefinery scenarios are analysed at a 10% discount rate with 2019 as the reference year. Configuration I using SCG from London coffee establishments yields a negative net present value (NPV) of −£3.9 million and 22% greater greenhouse gas (GHG) emissions than conventional rapeseed biodiesel production. Changing the SCG source to a coffee factory increases biorefinery size by 2.3 times but still produces a negative NPV. Using Configuration II to process SCG from coffee shops significantly improves NPV. However, without on-site energy generation, its GHG emissions are greater than those from conventional production methods of the high-value chemicals. An on-site Configuration I using SCG from the coffee factory yields the best performance. It produces a NPV of £3.1 million and GHG emissions 85% and 13% lower than that of SCG landfilling and conventional biodiesel. Overall, these findings demonstrate the potential of extracting value from SCG waste using a biorefinery approach, revealing a strong likelihood that future SCG biorefineries will be large scale and on-site of SCG production.