Automation In Wet Coffee Processing For Zero Liquid Waste
DOI:
https://doi.org/10.25186/.v21i.2413Abstract
Wet processing of cherry coffee generates liquid waste with high turbidity and acidity, creating a risk of environmental pollution. This study addresses the need for sustainable technology to achieve zero liquid waste in cherry coffee processing by evaluating the effectiveness of a Programmable Logic Controller (PLC)-based automation system in improving wastewater quality. The system integrates a filtration unit using silica sand and activated carbon with a water circulation mechanism controlled by real-time turbidity and pH sensors. Manual and automatic processes were compared in semi-wash and full-wash modes, with turbidity (NTU) and pH as the primary parameters. Experiments employed real-time sensing, two-way ANOVA, and Tukey HSD analysis. The manual semi-wash process increased turbidity from 0.429 ± 0.015 NTU to 5.219 ± 0.011 NTU and reduced pH from 7.216 ± 0.011 to 6.964 ± 0.022, while the manual full-wash produced turbidity of 7.811 ± 0.061 NTU and pH of 6.556 ± 0.017. In contrast, the automatic semi-wash only increased
turbidity to 0.467 ± 0.021 NTU, with pH remaining stable at 7.187 ± 0.017, and the automatic full-wash produced turbidity of 0.470 ± 0.023 NTU and pH of 7.274 ± 0.080. The automated system also enabled water recycling using turbidity and pH readings, without generating liquid waste. These findings indicate that the proposed technology can reduce water consumption by up to 100% while maintaining process quality and environmental sustainability. This research supports the transformation of the coffee industry toward cleaner and more sustainable practices, particularly in water-limited regions.
Key words: Programmable logic control; water quality; wet processing; water recirculation; turbidity control.
References
Agudelo-Escobar, L. M. et al. (2022). A bioelectrochemical system for waste degradation and energy recovery from industrial coffee wastewater. Frontiers in Chemical Engineering, 4:826576.
Beyene, A. et al. (2014). Experimental evaluation of anaerobic digestion for coffee wastewater treatment and its biomethane recovery potential. International Journal of Environmental Science and Technology, 11(7):1881-1886.
Campos, R. C. et al. (2021). New sustainable perspectives for "Coffee Wastewater" and other by-products: A critical review. Future Foods, 4:100058.
Cortés, Y. F. et al. (2020). Environmental impacts from coffee production and to the sustainable use of the waste generated. Produccion y Limpia, 15(1):93-110.
De Araujo, Á. A. et al. (2021). Comparison of the salt extract from Moringa oleifera seed in relation to Opuntia cochenillifera, tannin, FeCl₃, Al₂(SO₄)₃ and FeSO₄ as coagulants in coffee effluent treatment. Acta Horticulturae, 1306:277-284.
Djafar, Z. et al. (2025). Engineering innovation for cherry coffee wet processing using circulation system and agitator grading machine. Coffee Science, 20:e202276.
Fernanda, L. et al. (2023). Biological treatment of coffee honey water and its reuse for fertigation in king grass (Pennisetum Purpureum x Pennisetum Typhoide). Produccion y Limpia, 18(2):24-40.
Genanaw, W. et al. (2021). Effect of wastewater discharge from coffee processing plant on water quality of rivers in Sidama, Ethiopia. Environmental Health Insights, 15.
Ijanu, E. M. et al. (2020). Coffee processing wastewater treatment: a critical review on current treatment technologies with a proposed alternative. Applied Water Science, 10:53.
International Coffee Organization - ICO. (2024). Beyond Coffee: Towards a Circular Coffee Economy (2022/23 Overview). London: International Coffee Organization.
Kleinwächter, M., & Selmar, D. (2010). Influence of drying on the content of sugars in wet processed green Arabica coffees. Food Chemistry, 119(2):500-504.
Laili, N. et al. (2022). Design of sustainable coffee processing wastewater treatment system using K-means clustering algorithm. IOP Conference Series: Earth and Environmental Science, 1063:012032.
Pongsiriyakul, K. et al. (2024). Upcycling coffee waste: key industrial activities for a bio-circular economy. Processes, 12(12):2851.
Rattan, S. et al. (2015). A comprehensive review on utilization of wastewater from coffee processing. Environmental Science and Pollution Research, 22(9):6461-6472.
Rojas, E. M. et al. (2022). Water quality in small-scale coffee production units, Amazonas, Peru. OnLine Journal of Biological Sciences, 22(4):448-455.
Said, N. S. M. et al. (2021). Endurance of Phragmites karka in removing colour and suspended solids from industrial coffee processing effluents in a continuous reed bed system. Journal of Water Process Engineering, 40:101832.
Said, N. S. M. et al. (2023). Integrating treatment processes of coffee processing mill effluent for reclamation of secondary resources. Journal of Cleaner Production, 386:135837.
Setiawan, A. et al. (2025). Understanding the thermal and physical properties of biochar derived from pre-washed Arabica coffee agroindustry residues. Bioenergy Research, 18:16.
Tsigkou, K. et al. (2025). Coffee processing waste: unlocking opportunities for sustainable development. Renewable and Sustainable Energy Reviews, 210:115263.
Ulsido, M. D., & Li, M. (2016). Solid waste management practices in wet coffee processing industries of Gidabo watershed, Ethiopia. Waste Management and Research, 34(7):638-645, 2016.
Ulsido, M. D. et al. (2024). Waste water management in wet coffee processing mills and its implications Gidabo River Basin, Ethiopia. Environmental Systems Research, 18.
Widodo, P. B. et al. (2023). Efficacy of natural and full washed post-harvest processing variations on arabica coffee characteristics. Materials Today: Proceedings, 87:79-85.
Zhang, S. J. et al. (2019). Following coffee production from cherries to cup: Microbiological and metabolomic analysis of wet processing of Coffea arabica. Applied and Environmental Microbiology, 85:6.
Zungu, V. et al. (2022). Fabrication of biochar materials from biowaste coffee grounds and assessment of its adsorbent efficiency for remediation of water-soluble pharmaceuticals. Sustainability, 14:5.
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2026 Coffee Science - ISSN 1984-3909The copyright of the articles published in this journal belongs to the authors, with the journal holding the first publication rights. As the articles are published in this journal under open access, they may be freely used, with proper attribution, for educational and non-commercial purposes
