Valorization of Fruit and Vegetable Market Waste via Batch Anaerobic Digestion: Reactor Performance and Scope for Future Optimization

Abstract

In India, nearly 5.6 million tonnes of fruit and vegetable waste are generated annually, much of which ends up in landfills, causing odor, environmental degradation, and greenhouse gas emissions. This study investigates anaerobic digestion as a sustainable and cost-effective technique for converting such biodegradable market waste into biogas, a renewable energy source. A novel 20-liter batch anaerobic reactor was custom-fabricated and operated under mesophilic conditions (35°C) for 41 days using unsegregated market-derived fruit and vegetable waste, with cow dung as inoculum. Key parameters—including pH, chemical oxygen demand, total suspended solids, volatile suspended solids, and alkalinity—were monitored throughout the operation, and biogas production was measured using the water displacement method. A maximum removal of 70 percent chemical oxygen demand and a biogas yield of 19.13 milliliters per liter were achieved. Although the study duration was limited by the academic calendar, the system maintained stable performance despite acidic pH and high solids. The reactor’s low cost and simplicity highlight its potential for decentralized waste-to-energy solutions, especially when integrated with artificial intelligence-based real-time monitoring in future systems.

Introduction

India ranks second worldwide in fruit and vegetable production, generating significant waste (about 30% of production) due to its high moisture content and biodegradability. This waste often leads to environmental pollution if not managed properly. Anaerobic digestion (AD) is an effective biological method for treating these wastes, producing biogas and nutrient-rich effluent usable as bio-fertilizer.

The study evaluates a lab-scale anaerobic batch reactor digesting market fruit and vegetable waste mixed with cow dung inoculum at mesophilic conditions (35°C) over 42 days. Key physicochemical parameters, biogas production, and COD removal were monitored. Results showed:

• The pH remained slightly acidic due to volatile fatty acids but was buffered by cow dung.

• COD removal improved from 10% initially to 70% by Day 41, indicating effective organic degradation.

• Biogas production started after two weeks, increasing steadily to 19.13 mL/L.

• Total suspended solids (TSS) and volatile suspended solids (VSS) increased due to microbial growth and undigested solids.

Despite good biogas yield and COD reduction, the effluent’s COD and TSS levels remained above regulatory limits, suggesting that anaerobic digestion alone is insufficient. A combined treatment approach involving subsequent aerobic treatment and solids removal (e.g., Dissolved Air Flotation) is recommended for full compliance.

Conclusion

This study confirms that anaerobic digestion is a feasible method for converting fruit and vegetable market waste into biogas using a low-cost batch reactor system. Over a 41-day digestion period, the system achieved a maximum COD removal efficiency of 70% and biogas yield of 19.13 mL/L. Parameters such as TSS, VSS, and pH remained within biologically functional ranges, despite the acidic environment. However, effluent COD and TSS exceeded CPCB standards, indicating the need for secondary aerobic treatment. Advanced technologies like MBR, SBR, and MBR—along with Dissolved Air Flotation (DAF)—are recommended to meet discharge norms. Due to the course timeline, the reactor was terminated at the end of its initial operational period (42 days), representing the start-up phase. Future research should extend the operation to evaluate steady-state performance, optimize loading rates, and examine long-term gas production trends. The use of AI-enhanced monitoring systems is strongly encouraged to enable real-time process control, predictive analytics, and operational optimization in small-scale biogas systems for decentralized waste-to-energy applications.

References

[1] A. Singh, S. Kumar, P. Sharma, and A. Pandey, “Post-harvest losses in fruits and vegetables: A critical review,” J. Food Qual., vol. 2021, Art. no. 6672024, 2021. [2] Food and Agriculture Organization (FAO), Global Food Losses and Food Waste: Extent, Causes and Prevention, Rome: FAO, 2011. [3] L. Appels, J. Baeyens, J. Degrève, and R. Dewil, “Principles and potential of anaerobic digestion of waste-activated sludge,” Prog. Energy Combust. Sci., vol. 34, no. 6, pp. 755–781, 2008. [4] R. Tapia-Tussell, A. Martinez, N. Pacheco, E. Olguin-Maciel, and J. Dominguez-Maldonado, “Biogas production from fruit wastes: Reactor design and process optimization,” Waste Manag. Res., vol. 36, no. 7, pp. 627–636, 2018. [5] V. K. Sharma, C. Testa, G. Cornacchia, G. Lastella, and R. Farina, “Anaerobic digestion of semi-solid organic waste from vegetable markets: Experimental results,” Energy Convers. Manag., vol. 40, pp. 287–304, 1999. [6] A. B. Thomsen, G. Lissens, L. Baere, W. Verstraete, and B. Ahring, “Thermal wet oxidation improves anaerobic biodegradability of raw and digested bio-waste,” Environ. Sci. Technol., vol. 38, pp. 3418–3424, 2004. [7] F. Tambone, B. Scaglia, G. D’Imporzano, and F. Adani, “Assessing amendment properties of digestate by studying the organic matter composition and the degree of biological stability during the anaerobic digestion of the organic fraction of MSW,” Bioresour. Technol., vol. 102, no. 3, pp. 902–908, 2011. [8] A. Sharma, H. Jain, and A. K. Nema, “Assessment of market waste characteristics and potential for biogas generation in Indian urban context,” Renew. Sustain. Energy Rev., vol. 144, Art. no. 110966, 2021. [9] A. Buekens, “Energy recovery from residual waste by means of anaerobic digestion technologies,” in Conf. Future Residual Waste Management in Europe, 2005. [10] S. Ghosh, T. Pandey, A. K. Shukla, and A. Kumar, “Fruit waste management through anaerobic digestion: An emerging route for bioenergy recovery,” J. Environ. Manag., vol. 308, Art. no. 114667, 2022. [11] K. Jankowski, K. Nowak, and M. Wasilewski, “Challenges in anaerobic digestion of fruit waste: A comprehensive review,” Waste Biomass Valorization, vol. 14, pp. 215–232, 2023. [12] W. Parawira, Anaerobic Treatment of Agricultural Residues and Wastewater, Dept. of Biotechnology, Lund Univ., 2004. [13] V. D. Sridevi and R. A. Ramanujam, “Biogas generation in a vegetable waste anaerobic digester—An analytical approach,” Res. J. Recent Sci., vol. 1, no. 3, pp. 41–47, 2012. [14] A. D. Karve, “Compact biogas plant: A low-cost digester from waste starch,” ARTI Biogas Project, Pune, 2007. [15] American Public Health Association (APHA), Standard Methods for the Examination of Water and Wastewater, 23rd ed., Washington, DC, 2017. [16] Y. Chen, J. J. Cheng, and K. S. Creamer, “Inhibition of anaerobic digestion process: A review,” Bioresour. Technol., vol. 99, no. 10, pp. 4044–4064, 2008. [17] S. N. Misi and C. F. Forster, “Semi-continuous anaerobic co-digestion of agro-waste,” Environ. Technol., vol. 23, no. 4, pp. 445–453, 2002. [18] M. H. Igoni, M. F. N. Abowei, M. J. Ayotamuno, and C. L. Eze, “Effect of total solids concentration of municipal solid waste on biogas produced in an anaerobic continuous digester,” Sci. Res. Essays, vol. 3, no. 9, pp. 401–409, 2008. [19] R. Singh, S. K. Mandal, and V. K. Jain, “Development of mixed inoculum for methane-enriched biogas production,” J. Sci. Ind. Res., vol. 67, pp. 889–893, 2008. [20] Y. Li, Y. Jin, L. M. Shao, and P. He, “Anaerobic co-digestion of organic waste: A review on performance and microbial dynamics,” Bioresour. Technol., vol. 341, Art. no. 125960, 2021. [21] B. K. Ahring, Z. Mladenovska, R. Iranpour, and P. Westermann, “State of the art and future perspectives of thermophilic anaerobic digestion,” Water Sci. Technol., vol. 45, pp. 298–308, 2002. [22] Budiyono, M. Firliani, N. Amalin, A. M. H. Hawali, and S. Sumardiono, “Production of biogas from organic fruit waste using ruminant as the inoculum,” MATEC Web Conf., vol. 156, Art. no. 03053, 2018. [23] S. Baroutian, N. Eshtiaghi, and D. J. Gapes, “Dissolved air flotation for solid–liquid separation in industrial wastewater treatment,” Chem. Eng. Res. Des., vol. 165, pp. 280–292, 2021. [24] Central Pollution Control Board (CPCB), General Standards for Discharge of Environmental Pollutants into Inland Surface Waters, Notification GSR 422(E), MoEFCC, Govt. of India, 1986 (Updated 2018). [25] Z. Ahammad, M. M. Rahman, and H. H. Ngo, “Application of MBBR and MBR in treating food waste-derived leachate: A review,” J. Water Process Eng., vol. 53, Art. no. 103590, 2023. [26] B. Sarkar, S. Mukherjee, and B. Adhikari, “Performance evaluation of SBR and MBR for industrial wastewater treatment,” Environ. Technol. Rev., vol. 12, no. 1, pp. 1–15, 2023.

Copyright

Copyright © 2025 Venkatesh K. R, Ahamed Hilal A. R . This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.