It is known that electrodes made of carbon materials (graphite, glassy carbon, carbon paste or graphene) due to low ohmic resistance can significantly improve the electroanalytical properties of sensitive layers and provide a variety of modification options that are often used to develop highly sensitive sensors for investigation of electrochemical properties and give opportunity for detection of various compounds. The first goal of this work was to develop a simple electrochemical method for the determination of vitamin C (VitC) on a specially constructed microelectrode made from the Pyrolytic Graphite Sheet (PGS). Cyclic voltammetry was used to characterize the microelectrode and square wave voltammetry for electroanalytical purposes. A procedure for quantifying VitC in a real sample was established. VitC shows a single quasi–reversible reaction involving the transfer of two electrons, while the oxidation potential depends on the analyte concentration. SWV was optimized and analytical determination was performed in the potential range from –0.30 to 0.80 V. The obtained results show a linear response of the PGS electrode in a wide range of concentrations. The second goal was to determine the effect of adding different types of "green" biowaste on plant growth, VitC content and antioxidant activity in arugula (Eruca sativa L) using PGS electrode. The obtained results were compared with standardized methods. After three weeks of cultivation, small differences in growth and large differences in certain nutritional characteristics were observed. The addition of peanut shell contributes to soil aeration, and the fastest development of healthy and green Eruca sativa has been observed. The addition of black coffee makes the soil slightly alkaline and results in a significant increase in VitC content and antioxidant activity.