Spent coffee grounds as a non-structural embankment fill material: engineering and environmental considerations

In recent years, research into the engineering properties of highly organic materials have been undertaken to determine their engineering properties when used as road embankment fill materials. A prime contributor of organic wastes in municipal landfills is spent coffee grounds from cafes and domestic households. As part of this research, an extensive suite of engineering and environmental tests were undertaken on spent coffee grounds obtained from several popular cafes in Melbourne, Australia to evaluate their properties and potential use as a non-structural fill material in road embankments. The suite of engineering tests included, particle size distribution, Atterberg limits, particle density, standard compaction tests, static triaxial tests, oedometer consolidation, pH and organic content tests. In addition, a suite of chemical tests comprising leaching and polycyclic aromatic hydrocarbon tests were undertaken on the coffee grounds. From an environmental perspective, coffee grounds were found to pose no environmental and leaching issue for use as an embankment fill material. From an engineering material perspective, the high organic content, low maximum dry densities and high optimum moisture content restricts the usage of this material to non-structural fill applications where the material will not have to sustain high traffic loadings. The usage of spent coffee grounds as non-structural fill material in embankments was found to be a viable end-of-life option to divert coffee grounds from landfills and furthermore to maximize the naturally high organic content present in the coffee grounds for vegetation purposes.