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Caffeine’s Role in the Phytotoxicity of Spent Coffee Grounds

JSHS · 2024

Minsong Kim, Mr. Scott Bittner · Humphreys High School, Camp Humphreys, Republic of Korea

Overview

8 to 15 million tons of spent coffee grounds (SCG), the remainder left after brewing coffee grounds, is produced every year globally. To reduce waste in landfills, SCG has been proposed as an agricultural soil amendment due to its high organic content of carbon and nitrogen. However, raw SCG also has phytotoxic properties when added to soil, which has been largely contributed to its phenol compound and caffeine content. This study seeks to isolate the effects of caffeine within SCG to determine whether or not caffeine has an inhibitory or enriching effect on plant growth. It was hypothesized that decaffeinated SCG would have less of an inhibitory effect on plant growth in comparison to caffeinated SCG when administered as a soil amendment. Three treatment gr oups were created within the design of the experiment (Control, Caffeinated, and Decaffeinated). 3.5% (w/w) of caffeinated and decaffeinated SCG was administered to the agricultural soil before planting Lactuca sativa seeds. The control group had no SCG ad ministered. Both the caffeinated and decaffeinated SCG were treated via the conventional solvent extraction method to reduce the inhibitory effect of phenol compounds. The control group significantly outperformed both other treatment groups. However, when comparing the caffeinated and decaffeinated groups, the larger mean biomass of the caffeinated group would suggest that the caffeine within SCG promoted plant growth. These results are in direct contrast to the hypothesis and previous ideas regarding caffe ine as a phytotoxic compound within SCG.

Competition history

  • JSHS 2024 Category not listed

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Source: Junior Science and Humanities Symposium

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