An assessment of spent coffee grounds as a replacement for peat in the production of Scotch whisky: chemical extraction and pyrolysis studies

The potential of spent coffee grounds (SCG) to act as a replacement fuel material for the malt-drying process during whisky production was evaluated. The extracts of both materials, and the smoke they produced through burning, were subjected to analysis by high resolution 1H NMR spectroscopy. Malts infused with the smokes were similarly studied to gain an understanding of the transfer of chemical species from smoke to grain. In addition, the thermal degradation of peat and SCG were investigated using thermogravimetric analysis and pyrolysis – GCMS. Our studies revealed that, despite some chemical differences between the source materials, the composition of the smoke produced by both is remarkably similar. It may be concluded that the aroma and flavour of the spirit, resulting from substitution of peat by SCG is also likely to be similar, however the presence of additional congeners in the SCG-derived spirit, including furans and methylpyridines, could introduce undesirable off notes.