I. Roasted Coffee Production and the Demand for Wastewater Reduction

The coffee production process consumes large volumes of water resources and simultaneously generates significant amounts of wastewater and sludge, impacting the environment. While numerous technologies and equipment are available for coffee wastewater treatment, not every factory can access cost-effective solutions that effectively reduce emissions.

II.Roasted Coffee

In the roasted coffee production process, coffee beans must undergo processing to remove the outer pulp and dry the beans before roasting. Two primary methods are used: wet processing and dry processing. Each method involves specific steps that influence the flavor and quality of the coffee.

a. Coffee Processing Using the Wet Method: 

1. Harvesting → 2. Wet processing → 3. Drying → 4. Milling and sorting → 5. Coffee roasting → 6. Cooling and curing → 7. Grinding → 8. Packaging

The wet method is a complex process requiring various machinery and significant water usage, typically applied to Arabica coffee processing.

This method produces coffee beans with bright, clean flavors, often used for high-quality coffee.

 

Process and Wastewater Characteristics in the Wet Method:

Wet-Processing Method for Roasted Coffee Production	Tasks Performed	Characteristics of Generated Wastewater
1.Harvesting	Coffee is harvested when the coffee cherries are fully ripe. In Vietnam, the harvesting method is typically selective harvesting (picking only ripe cherries by hand) or mass harvesting (picking both ripe and unripe cherries).	Roasted coffee processed by the wet method typically generates a larger volume of wastewater compared to other methods. Wastewater generated from production activities exhibits high pollutant concentrations, primarily originating from bean processing stages such as soaking, depulping, fermenting, and cleaning: Suspended Solids (TSS): The wastewater often contains a high level of suspended solids, primarily from soil, sand, dust, defective cherries, leaves, and fragments of coffee cherry husks, as well as pulp and residual flesh from the coffee beans during the cleaning process. High Organic Content (COD, BOD): The wastewater is rich in organic compounds, mainly from the husks, pulp, and fruit flesh of the coffee cherries, along with dissolved substances. Low pH: The fermentation process releases organic acids, resulting in acidic wastewater with a pH typically ranging from 3.5 to 5.5. Color: The wastewater is characterized by a dark brown to black color due to the presence of polyphenols and organic pigments from the coffee. Nitrogen and Phosphorus: The wastewater contains relatively high levels of nitrogen and phosphorus, derived from the natural decomposition of nitrogen- and phosphorus-containing compounds in the coffee cherries. Odor: The wastewater emits a characteristic foul odor due to the decomposition of organic matter and anaerobic fermentation (if it occurs). Microbial Load: The wastewater contains a high microbial load from the fermentation process, including some bacteria and microorganisms that may pose risks if discharged untreated into the environment. Wastewater generated from cleaning the workshop and equipment: Source: This wastewater primarily comes from washing and cleaning the equipment and workshop area. TSS Concentrations: The wastewater exhibits high TSS levels, mainly from coffee particles and residues spilled during the production process, as well as from equipment and floor cleaning. BOD and COD Levels: Organic pollutants in the wastewater originate from coffee grounds, defective coffee beans, or residuals left on equipment surfaces. Cleaning Agents: The wastewater may contain cleaning chemicals used for sanitizing machinery and the workshop. Oil and Grease: Oil and grease residues are generated from cleaning machinery components.
2. Processing beans by the wet method:	Step 1: Soaking and sorting the cherries Step 2: Depulping and removing the fruit flesh Step 3: Fermentation Step 4: Washing
3. Drying	After depulping, the coffee beans must be dried either in the sun or by using a dryer to reduce the moisture content to about 10-12% to ensure the beans do not mold or spoil during storage.
4. Hulling and sorting	Once the coffee beans have been dried, the hulling process begins. The beans are placed into hulling machines to remove the outer parchment layer, leaving only the green coffee beans (unroasted coffee). The green coffee beans are then sorted by size, weight, and quality to ensure uniformity before roasting.
5. Roasting coffee	The green coffee beans are placed into a roasting machine at a temperature of approximately 180-240°C for 8 to 20 minutes (depending on the type of coffee and roasting style).
6. Cooling and resting:	The beans may be cooled by air or water (depending on the roasting method). After cooling, the coffee needs to rest for 24 to 48 hours to allow the flavors to stabilize.
7. Grinding coffee	Roasted coffee can be ground into powder (fine, medium, or coarse) or left as whole beans, depending on the intended use.
8. Packaging	The roasted coffee, after being ground or left as whole beans, is then packed securely to preserve freshness.

 

b. Coffee Processing Using the Dry Method:

Dry processing, also known as the natural method, is traditional and simpler. Coffee processed this way has a sweeter, heavier body with fruity notes.

In Vietnam, the dry method remains the primary approach, particularly for Robusta coffee, which constitutes approximately 90% of the country’s coffee production.

1. Harvesting → 2. Dry processing → 3. Drying → 4. Milling and sorting → 5. Coffee roasting → 6. Cooling and curing → 7. Grinding → 8. Packaging

Process and Wastewater Characteristics in the Dry Method :

Dry-Processing Method for Roasted Coffee	ProductionTasks	PerformedCharacteristics of Generated Wastewater
1. Harvesting	Coffee is harvested when the coffee cherries are fully ripe. In Vietnam, the common harvesting methods are selective harvesting (handpicking ripe cherries) or batch harvesting (picking both ripe and unripe cherries).	Roasted coffee processed by the dry method typically generates less wastewater compared to other methods because the dry method primarily relies on natural sun-drying and does not use water in the main steps of the process. Wastewater is mainly generated from the cleaning of the production facility and equipment: In large processing facilities, the regular cleaning process to sanitize machinery and floors can produce a certain amount of wastewater containing dirt, coffee grounds, and impurities from the production process. Suspended solids (TSS): Wastewater from the cleaning process may contain suspended solids (TSS) such as dirt, coffee husk residue, and other debris from cleaning the coffee beans and the grounds scattered during the production process, as well as from cleaning equipment and floors. Organic matter (COD, BOD): Although there is not a large amount of organic material from the main production process (because water is not used for fermentation or depulping), wastewater from cleaning may still contain small amounts of organic matter from coffee grounds, husks, and other parts of the coffee cherries. This can increase COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) in the wastewater, but at lower levels. pH: Wastewater from this process typically has a near-neutral pH (ranging from 6.0 to 7.0) because there are no strong chemical reactions or fermentation occurring during dry processing. Color: Wastewater may have a light brown color due to impurities from coffee grounds or soil debris from the coffee cherries, but it is not as dark as in wet processing. Cleaning agents: Cleaning agents used for sanitizing machinery and the facility. Oils and fats: Oils and fats generated from the cleaning of machinery.
2. Processing the beans using the dry method:	Step 1: Dry the whole cherries. Step 2: Remove the outer skin. Step 3: Clean and sort.
3. Drying	After the outer skin is removed, the coffee beans must be dried, either by sun-drying or mechanical drying, to reduce moisture content to about 10-12% to ensure the beans do not mold or spoil during storage.
4. Hulling and sorting	After the coffee beans are dried, the hulling process begins. The beans are placed in hulling machines to remove the outer parchment layer, leaving only the green coffee beans (unroasted). The green coffee beans are then sorted by size, weight, and quality to ensure uniformity before roasting.
5. Roasting	The green coffee beans are placed in a roaster at temperatures between 180-240°C for about 8 to 20 minutes (depending on the type of coffee and roasting style).
6. Cooling and resting	The beans can be cooled by air or by water (depending on certain roasting methods). After cooling, the coffee needs to rest (from 24 to 48 hours) for the flavors to stabilize.
7. Grinding	The roasted coffee can be ground into powder (fine, medium, or coarse grind) or left whole depending on the usage requirements.
8. Packaging	The roasted and ground coffee, or whole beans, are sealed and packaged for storage.

III. Limitations of Current Coffee Wastewater Treatment Solutions

Current treatment methods for coffee production wastewater often combine:

1. Mechanical Treatment: Sedimentation and filtration to remove suspended solids.
2. Chemical-Physical Treatment: Coagulation and oil separation to eliminate insoluble substances and grease.
3. Biological Treatment: Aerobic and anaerobic processes for organic matter decomposition.
4. Membrane Technology: Enhances treated water quality.

The current coffee wastewater treatment methods can handle most pollution levels to meet environmental discharge standards and are widely applied in many coffee production facilities in Vietnam. However, considering multiple factors such as treatment efficiency, cost, feasibility, and environmental impact, there are still several limitations:

• Large Space Requirements:
  The construction of treatment tanks requires significant space, which can be challenging for businesses that need to prioritize land for production.
• High Discharge Volume and Costs:
  The large volume of wastewater discharge and monthly discharge fees for industrial parks or clusters represent a substantial financial burden.
• High Sludge Volume:
  The significant amount of sludge generated during the process requires additional treatment, increasing overall costs.
• Sensitivity of Biological Treatment Methods:
  Biological treatment methods are quite sensitive to fluctuations in pollutant loads. Many plants face operational challenges, with frequent incidents occurring during operation.
• High Energy Consumption:
  The high electricity consumption indirectly increases greenhouse gas emissions.

IV. Solutions from NGO International Co., Ltd

We understand that businesses strive to enhance their market competitiveness while meeting the increasingly stringent requirements for sustainable development, including certifications such as Rainforest Alliance, UTZ Certified, and Fair Trade.

NGO has dedicated years to gathering operational data from coffee production plants in Vietnam, as well as performance data from coffee wastewater treatment facilities, to research and develop solutions that focus on energy conservation and resource reuse. Our key objectives include:

• Land Resource Optimization:
  Wastewater treatment plants are designed with high efficiency, allowing a 50% reduction in construction space.
• Energy Savings:
  For plants with high pollution concentrations (COD ~ 10,000–20,000 mg/L), we ensure energy consumption remains below 3 kWh/m³.
• Water Resource Reuse and Sludge Reduction:
  • Reusing Treated Water: NGO advises on wastewater reuse strategies at various levels to optimize total water consumption per ton of product.
  • Reducing and Recycling Production Sludge: Treatment plants are designed to prioritize reusing sludge for fertilizer production or recycling it into raw materials, contributing to waste reduction and supporting the circular economy model.
• Chemical Reduction:
  By employing biological treatment methods with high input fluctuation tolerance, we stabilize system operations while minimizing emissions and environmental impact.
• Climate Change Adaptation:
  Future wastewater treatment plant designs consider resilience to weather and climate changes, such as heavy rainfall, flooding, or droughts, ensuring stable operations under extreme conditions.

NGO International Co., Ltd is committed to providing the most advanced and modern technologies to help businesses not only reduce emissions but also enhance production efficiency and protect the environment.

Contact us to learn more about our wastewater treatment solutions for roasted and ground coffee production. Reach us at 024.7300.0890 or email office@8ngo.com for direct consultation.