The influence of addition of spent coffee grounds and their refining products on psychical a chemical properties of a soil and a growth of Lactuca sativa

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angličtina

Annual worldwide production of spent coffee grounds (SCG) is more than 8,5 mil tonnes. Most of this amount is landfilled or incinerated. However, after the different refinery processes (acid hydrolyse, extraction, defatting) SCG could be used as a substrate for production of biodiesel, bioethanol or polyhydroxyalkanoates. Thanks to its elemental composition it appears to be a potential soil enrichment material. The aim of this pilot study was to evaluate the influence of the addition of untreated SCG as well as its acid hydrolysed, defatted and oxidized forms to a base clay soil, which is due to its low content of phosphorus and potassium impropriate for plant cultivation. Samples of SCG were added to the base soil in 2% w/w. The influence of the addition of SCG samples on pH, conductivity and content of extractable elements (Ca, K, Mg, P, Al, Fe, Mn, Na, Cu, Cr) were determined. Cultivation of Lactuca sativa was carried out in all mixture of a base soil and SCG samples for 3 weeks. As a reference for measuring data, samples of base soil and base soil with addition of a commercial NPK fertilizer were used. Measurements revealed significant effects on psychical and chemical properties of soil. Decrease of pH and an increase in conductivity was observed in all tested mixtures. The lowest pH (6,57) and the highest conductivity (1295 µS·cm-1) were observed in acid hydrolysed SCG samples. In all soil samples, the significant increase up to 50 % of extractable Ca, Mg, and Mn was observed. On the other hand, during 3 weeks the addition of SCG samples did not significantly enrich the soil by P and K. In the growth experiments it was found, the addition of the substrates did not significantly promote growth in comparison with control sample. Germination of seeds were completely inhibited in soils enriched by hydrolysed SCG. In defatted and oxidized samples, the early germination and the highest number of plants were observed. The deficiencies of P and K had a great impact on growth rate and visual appearance of cultivated Lactuca sativa. In comparison with the base soil with NPK addition, plants had pink colour and lower growth. Due to the acidity of SCG, its application is more suitable to alkaline soil. It can enrich the soil by Ca, Mg or Mn, but it is not able to supply P and K in relative short time. Its potential as a source of elements could be better utilized after composting or in a form of a bio-char.

Spent coffee grounds, refinery, agriculture, soil, fertilizers

Slavíková Z.; Pořízka J.; Diviš P.

21. 11. 2019

Vysoké učení technické v Brně, Fakulta chemická

978-80-214-5807-9

Studentská odborná konference Chemie je život 2019

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