1000kg of fresh berry gives about 400kg of wet waste pulp and only 160kg of exportable green bean (Source: Jan von Enden - An Introduction to Good Manufacturing Practices for Post Harvest Processing of Arabica Coffee in Vietnam). Coffee pulp is mainly composed of water and sugar. The sugar can be fermented by bacteria and acidified, resulting in a bad smell. The water leaking from the pulp can be highly acidic. Hence, treating waste pulp is as important as treating the wastewater.
There are several ways in which this by-product can be utilised.
Composting: Coffee pulp is a source of nutrients: 0.5% of composted pulp is nitrogen, 0.15% is phosphorus, and 0.5% is potassium. Therefore, pulp can be treated and used as organic fertiliser. The pulp is left in piles, and after 3 to 12 months, it turns into rich, black humus, and can be used for composting. Another way of composting is to mix coffee husk with cattle manure, and leave the mixture in pits or heaps.
The use of organic fertiliser helps to improve soil properties thus increasing yield as shown through investigations in Columbia. Using organic fertilisers also helps to reduce the need to buy inorganic fertilisers, hence saving the farmers money .
Mushroom production: Coffee pulp can be used as planting soil for mushroom production. After being fermented for two days, the pulp is pasteurised with hot water, drained, dried, and mixed with mushroom spores. Then, they are put in plastic bags. After 3 - 4 weeks, the mushroom grow out of the holes in the bags and are collected. One bag allows 2 - 3 mushroom-harvests.
The mushroom can be eaten or dried and sold in the market. Considering the large amount of coffee pulp generated every harvesting season, the income from mushroom growing is significant for farmers.
Animal feeds: As it is rich in nutrients, coffee pulp can be dried and used in animal feeds. If used this way, the pulp needs to be treated as soon as possible to prevent the development of fungi. The pulp can be treated with Ca(OH)2 (calcium hydroxide) and be dried under pressure. Alternatively, the pulp can be mixed with sugar cane molasses, or urea and other inorganic substances and put in silos. The silage can be used after 3 weeks, and can be stored up to 18 months.
However, using coffee pulp as animal feeds is of limited value, since the cost for drying the pulp sometimes exceeds the gain. Besides, the effects of caffeine, tannin and the high level of potassium on the animal's health are unknown.
“An Introduction to Good Manufacturing Practices for Post Harvest Processing of Arabica Coffee in Vietnam” - Jan. C von Enden.
Animal Feed Resources Information System of FAO (Food and Agriculture Organization of the United Nations)
INeedCoffee – articles by Dr. Anand Titus and Geeta N. Pereira
On the Road to Quality. Made by Kraft foods Germany, Vietnam Coffee Cocoa Association VICOFA and Dtsch. Gesellschaft für technische Zusammenarbeit (Gtz).
Mr. Jan C. von Enden
EDE Consulting Asia Pacific
Dr. Anand Titus Pereira and M. S. Geeta Pereira