Πάντζαρης, Νικόλαος-ΙάσωνPantzaris, Nikolaos-Iason2026-10-202026-10-202026-10-05https://hdl.handle.net/10889/33238Nowadays, the amount of food waste produced is increasing, resulting in serious environmental, social and financial impacts. Almost one third of the annual food produced is wasted or lost, while the food waste that is left to degrade naturally in agricultural sites or landfills releases high amounts of greenhouse gases thus exacerbating the climate crisis [1]. According to statistics, 70.3 million tons of oranges were produced between 2013 and 2014 in Spain, while only 40% of the orange fruit mass is consumed leading to 42.2 million tons of food waste with the biggest portion being orange peels [2]. The present work investigates the reduction of food waste by utilizing it as raw material for the production of value-added products through bioprocesses based on the circular economy model. Specifically, the current experimental research uses orange peel waste for the production of both bacterial cellulose and biogas, obtaining the latter through anaerobic digestion. Initially, orange peels were processed to extract a liquid phase containing reducing sugars that were used as the carbon source for the bioproduction of bacterial cellulose by Komagataeibacter sucrofermentans; and a solid phase with the orange peel waste. Both the remaining liquid and solid waste fractions were used as substrates in the anaerobic process, in order to maximize the utilization of the waste under study, fostering the circular economy model and contributing to a more sustainable production process. In anaerobic digestion, two additives were investigated to enhance both bacterial cellulose production and biogas production, acetic acid and different types of biochar. The addition of 3 g/L of acetic acid in the orange peel culture medium during bacterial cellulose production was the most efficient concentration, resulting in optimal bacterial cellulose production and yield 3.055 ± 0.188 g/L and 0.589 ± 0.036 g/g respectively. Comparing the bacterial cellulose production to the commercial and more expensive HS culture medium, the orange peel culture medium resulted in higher bacterial cellulose production. As for the anaerobic digestion the results showed that the highest performance was observed for the samples with the orange peel waste containing 3 g/L and 9 g/L of acetic acid. Both of them reached the highest biomethane yield (mL/ gVS). Among these the sample with 3 g/L of acetic acid was considered the optimal due to lower production cost. Further investigation was performed in the anaerobic digestion by applying optimum acetic acid concentration and adding different types of biochar. Although, the literature suggests that the addition of biochar can enhance the biogas production, the results of the current study resulted in a lower methanogenesis compared to the control group. Specifically, the samples containing orange peel waste with 3 g/L of acetic acid and without the addition of any type of biochar resulted in 263.6 ± 0.8 mL/gVS, while the optimal sample containing biochar was the one with 10 g of orange peel biochar reaching a methane production of 222.7 ± 7.1 mL/gVS. Most of the tests containing biochar led to significantly lower hydrogen sulfide production comparing to the control group while others led to the significant reduction of the lag phase. Overall, the present strategy is very promising as it follows a sustainable approach based on the circular economy model and shows promising results.enCC0 1.0 UniversalBioprocessBacterial celluloseBiogasCulture mediumBiocharΒιομάζαΒιοαέρια