Depulping coffee

Coffee wastewater, also known as coffee effluent, is a byproduct of coffee processing. Its treatment and disposal is an important environmental consideration for coffee processing as wastewater is a form of industrial water pollution.

The unpicked fruit of the coffee tree, known as the coffee cherry, undergoes a long process to make it ready for consumption. This process often entails use of large quantities of water and the production of considerable amounts of solid and liquid waste. The type of waste is as a result of the type of process that the coffee cherries go through. The conversion of the cherry to oro or green bean (the dried coffee bean which is ready to be exported) is achieved through either a dry, semi-washed or fully washed process.

The coffee cherries are dried immediately after they are harvested through sun drying, solar drying or artificial drying. In sun drying, the coffee cherries are placed on a clean floor and left to dry in the open air. In solar drying, the cherries are placed in a closed cabinet, which has ventilation holes to let moisture out. Artificial drying is used mostly during the wet season, when the low level of sunlight extends the time needed for solar drying and the cherries are prone to mold growth. After being dried, the cherries are hulled. In this process the dried outer layer of the cherry, known as the pericarp, is removed mechanically.

In semi-washed processing, the cherries are de-pulped to remove the pericarp. After this the slimy mucilage layer which covers the bean is removed. This is done mechanically by feeding the beans into a cylindrical device which conveys them upward. While the friction and pressure exerted on the beans by this process is enough to remove most of the mucilage, a small amount of it will still remain in the centre-cut of the beans. This technique is used in Colombia and Mexico in order to reduce the water consumption from the long fermentation process and the extensive washing.

In order to reduce the contamination generated by the wet process of coffee fruits, scientists at Cenicafé developed a technology that avoids using water when not needed and uses the right water when needed. The technology, called Becolsub (taken from the initials of the Spanish for ecological wet coffee process with by-products handling: Beneficio Ecologicos Sub-productos), controls more than 90% of the contamination generated by its predecessor. The quality of the coffee processed this way is the same as for coffee processed by natural fermentation.

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Wikipedia