tags: [] - coffee/processing - coffee/equipment aliases: - Coffee wet mill - Beneficio húmedo - Washing station

Wet Mill¶

Tags: #coffee/processing #coffee/equipment Aliases: Coffee wet mill, Beneficio húmedo, Washing station Related: Coffee Processing MOC | Wet Process | Fermentation | Washed Processing | Natural Processing Status: ✅ Complete

Overview¶

A wet mill (also called a washing station, beneficio húmedo in Spanish, or coffee washing station in East Africa) is the facility where freshly harvested coffee cherries are processed using the washed (wet) method — received, sorted, depulped, fermented, washed, and dried to produce parchment coffee ready for milling and export. In the specialty coffee supply chain, the wet mill is often the critical quality control point: decisions about cherry receiving standards, fermentation protocol, and drying management at the wet mill determine the quality ceiling of the finished green coffee. Many specialty importers and roasters work directly with specific washing stations as part of direct trade relationships.

Key Equipment and Areas¶

Area / Equipment	Function
Receiving hopper	Cherry intake; initial volume assessment
Flotation channel	Sorts cherries by density; floaters (underripe, damaged) removed
Depulper	Mechanically removes outer skin (exocarp) from the cherry
Fermentation tanks	Concrete, tiled, or plastic tanks where parchment ferments 12–36 hours
Washing channels	Running water channels where fermented mucilage is washed off; density sorting occurs
Raised drying beds	Elevated mesh or netting tables allowing airflow around parchment during drying
Patios	Concrete drying surfaces; lower airflow than raised beds
Covered drying area	For protection from rain and direct sun during drying

Wet Mill Scale and Ownership¶

Wet mills range in scale from: - Smallholder cooperative stations: Serve hundreds to thousands of small producers delivering cherry by weight; East African model (Kenya, Rwanda, Ethiopia cooperatives) - Estate wet mills: Process only one farm's production; allow direct control of quality throughout - Large commercial beneficios: Process large volumes from multiple farms; primarily for commercial-grade coffee

In Kenya, the cooperative-owned wet mill (often called a "factory" in local terminology) is the central institution of coffee production — producers are members, and the station processes and markets their coffee collectively.

Quality Indicators¶

Quality wet mills typically feature: - High cherry receiving standards (only ripe red cherry accepted) - Controlled fermentation with endpoint monitoring (wash test) - Clean water supply for fermentation and washing - Raised drying beds rather than patios (better airflow and drying consistency) - Trained staff for sorting and drying management - Water recycling or treatment to manage environmental impact

Key Facts¶

A wet mill processes washed coffee from cherry intake through sorting, depulping, fermentation, washing, and drying
The wet mill is the primary quality control point for washed coffee — fermentation management and drying determine cup quality
Equipment: flotation channels, depulpers, fermentation tanks, washing channels, raised drying beds
Scale ranges from smallholder cooperative stations to large commercial beneficios
In East Africa, cooperative-owned washing stations are central institutions of specialty coffee production

References¶

Changelog¶

Date	Change
2026-04-28	Note created

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