Unlocking the potential of coffee pulp

The pulp problem

A major problem of the coffee industry nowadays is the huge amount of coffee waste that is dumped once the coffee beans are separated from the coffee cherries. For every kilogram of roasted coffee that we consume an equal amount of waste is left behind in the producing countries. When this waste is being disposed of, it pollutes the environment by leaching toxic compounds into rivers, lakes and soil.

The pollution generated from one ton of green coffee is equivalent to the pollution of domestic sewage output of 2.000 households. The high biological and chemical demand of oxygen (B.O.D. and C.O.D.) make it almost impossible for the waste to start oxidation and fermentation to become compost. Pectcof can prevent the formation of waste, by transformation of the coffee cherries into valuable bio compounds, consequently detoxifying them.

Coffee pulp being piled up in the coffee wet mills

 

Disposal of coffee pulp in the coffee regions

 

Process water from a wet mill, to produce 1kilogram of green beans 20 liters of water are needed.

 

Most of the coffee nowadays is processed using the wet method with variations to lower water consumption and control over the drying process (semi-dry, natural pulping etc.). Nevertheless, relative large amounts of biomass are still dumped into rivers. Nowadays, most of the coffee pulp goes without treatment directly to huge waste disposal sites without any treatment, eventually toxic compounds from the fermenting cherries leach to the rivers, polluting the sources of water in the coffee producing regions.

Coffee pulp therefore poses a serious environmental problem, and is a challenge to the sustainability of the coffee supply chain. With the actual production of coffee reaching 10 million tons per year, technology to exploit this waste stream is necessary. Currently coffee pulp is in general used only as compost. There has been research in the use of coffee pulp as feed for dairy cattle in Central and South Americas. Nevertheless, these practices use only a small percentage of the whole stream due to the anti-nutritional and toxic compounds in the biomass.

The Pulp Potential

With the production of coffee, coffee pulp is produced. Regardless of the source (wet or dry processing), by-products and waste products are often problematic. For example, pulp and mucilage are relatively acidic, corrosive to equipment, and difficult to safely dispose. Furthermore, where the pulp is discarded in a landfill or other disposal site, rotting pulp may lead to unpleasant smells. Therefore, by-products and waste products have often been viewed as materials which are either unusable, hazardous, or of negligible value.

Coffee pulp represents 45% of the total weight of the coffee cherry. The pulp biomass is rich in carbohydrates, polyphenols and caffeine. Because the high contents of organic acids, cathechins, and tannins, the coffee pulp and process water pose a serious environmental problem in the regions where production takes place. Coffee discarded streams (the pulp and process water used to separate the mucilage from the bean in the wet milling factories) have a high BOD (biochemical oxygen demand), which threatens water sources.

Wet Method

In the wet method, the cherries are collected and pulped fresh, leaving the mucilage (endocarp) and the silver skin attach to the beans; after pulping the beans go to fermentation tanks for period in general in the range of 12-24h in which the mucilage is released from the beans and silver skin. The beans then are dried (sun or hot air dried), the silver skin is removed and the green beans are packed and stored for further trade. During these processes about 45% of the coffee cherry biomass is discarded as waste material. This biomass has high content of polyphenols and caffeine, and therefore becomes toxic in high concentrations. Although composting is an alternative, big extensions of land and hard labor are necessary. On top of these requirements, the high concentration of polyphenols makes of the use of this compost a poor fertilizer with the risk of poisoning the soil and making it acidic.

Dry Method

In the dry method, the coffee cherries are dried, especially under the sun, for – in general - several days. Thereafter, the dried pulp is separated from the green beans by pulping. This method does not easily allow control of the drying process and may therefore generate a low(er) quality coffee.

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