Spent coffee grounds (SCG) as well as chicken (CES) or duck eggshells (DES) left over from the artificial hatching technology are proposed as potential soil improver and/or organic-mineral fertiliser components. Therefore, it seems interesting and necessary to evaluate the chemical composition of these wastes and their mixtures in terms of their possible use for that purpose. The study was conducted under the incubation experiment conditions using a mixture of SCG and eggshells (10:1 ratio). Macronutrients, i.e. C, N, S, were determined by the catalytic combustion method, while P, K, Mg, Ca, Na by atomic spectrometry. It was found that SCG were rich in C, N, P, and K, while eggshells in Ca, Mg, Na, and S. However, CES compared to DES were richer in deacidifying components (i.e. Ca, Mg, K). At the same time, the content of macronutrients in eggshells decreased gradually along with the embryo development. For this reason, the mixture of SCG and shells of unembryonated chicken eggs (CES I) had the best chemical and usable proprieties. To conclude, the chemical properties of the mixtures of spent coffee grounds and eggshells indicate their possible application in soil bioengineering.
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