MODIFICATION OF SPENT COFFEE GROUNDS AS ORGANIC FERLIZER

abstrakt

angličtina

Sustainable agriculture has many requirements on fertilizers, protection of plants and the environment. It can be the reason of increasing demand for natural fertilizers. Especially organic matter from household waste, which is not contaminated, might be used for production of ecological fertilizers. Consumption of coffee is increasing; the use of coffee was approximately 9,3 billion tuns per year 2016 and it is related to generating of waste named coffee grounds. Coffee grounds is insoluble part of coffee, which create 70 % of mass. This kind of waste is produced at each preparation of coffee. Relatively easy separation of coffee ground from other waste is big advantage for secondary use. Coffee ground consist high amount of oil, saccharides, antioxidants, minerals and other substances (1). High amount of mineral substances (N, K, O, Mg and Ca), organic carbon (2, 3), high sorption capacity (4) and good cation exchange capacity (5) create from coffee grounds perspective material for use in agriculture. This physical property may be related to higher fibber content. Fibber in the coffee ground would also supplement organic matter in the soil, which is not only essential for microbial life in the soil. On the other hand, many studies discuss negative effects of coffee grounds on plants. Negative influence can be caused by low C:N ratio and presence of phytotoxic substances (5, 6). Even a significant improvement in physical properties sandy soil did not prevent the negative effects of the previously mentioned parameters on plants (5). Its agronomic potential is uncertain, due to organic waste could contain a number of phytotoxic substances as phenolic compounds, organic acids, heavy metals. Phytotoxicity of these substances is testing by seed germination bioassays. Some of some of the phytotoxic substances could be used as an organic pesticide. Moreover, coffee grounds contain high amount of carbon (>58 %) and low concentration of natrium (˂2,0 %), which causes high ration of C/N to value 20-25 (Pujol et al., 2013). In this study, we tested several modifications of SCG, in order to reduce the concentration of phytotoxic compound in SCG, which mitigated inhibited plats growth. These procedures were based on fat, caffeine and phenolic compounds removal using different solvents or oxidizing substances. The possibility of using modified SCG as an organic fertilizer was tested in pot experiments with Lactuca sativa L. as experimental plant in two different soils. The use of SCG with the addition of wheat bran or biochar made from wheat bran was also tested. The pilot results from the growth experiment showed that the direct use of SCG, wheat bran or biochar in agriculture in the form of organic fertilizer and at the monitored mass concentration needs to be revised. A negative effect on the growth of the model plant Lactuca sativa L. was observed when the studied addition of 2.5 % of the substrate to the soil. It may increase the concentration of some macroelements in the soil (especially potassium and phosphorus). However, even coffee grounds modification and improvement of the physical properties did not prevent the negative effect of low C:N ratio on lettuce.

Coffee ground, organic fertilizer, Lactuca sativa, soil modification

JUGLOVÁ, Z.; DIVIŠ, P.; POŘÍZKA, J.

8. 1. 2024

International Ecological Engeneering Society

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