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WET COFFEE PROCESSING WASTE MANAGEMENT PRACTICE IN ETHIOPIA

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 Available Online at http://www.journalajst.com
ASIAN JOURNAL OF
SCIENCE AND TECHNOLOGY

Asian Journal of Science and Technology

ISSN: 0976-3376 Vol. 6, Issue 05, pp. 1467-1471, May, 2015

RESEARCH ARTICLE
WET COFFEE PROCESSING WASTE MANAGEMENT PRACTICE IN ETHIOPIA
1*Asrat Gebremariam Woldesenbet, 1Belay Woldeyes and 2Bhagwan Singh Chandravanshi
1School
of Chemical and Bio-Engineering, Addis Ababa Institute of Technology, Addis Ababa University,
P.O. Box 385, Addis Ababa, Ethiopia
2Department of Chemistry, Faculty of Sciences, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia

ARTICLE INFO ABSTRACT

Article History: Coffee is one of the most important agriculture commodities in the world. Ethiopia had been the origin
Received 15th February, 2015 of coffee because coffee plant was initially found and cultivated in the Kaffa province. Due to the great
Received in revised form demand of coffee, large amounts of residues are generated in the coffee industry, which are toxic and
24th March, 2015 represent serious environmental problems. 100 kg of fresh berry gives about 40 kg of wet waste pulp.
Accepted 02nd April, 2015
Published online 31st May, 2015
Coffee pulp contains caffeine, tannins, polyphenols and organic solid residues. It shows toxic nature
and thus not been utilized beneficially. This effluent is being directly discharged to the nearby water
bodies causing severe ailments like overexcitement, skin irritation, stomach pain, nausea and breathing
Key words: problem. Severeness of this waste causes a serious environmental problem among the residents of
Wet Processing, nearby area. For this reason, efforts have been made to develop methods for coffee waste treatment and
Coffee Effluent, management, also its utilization as a raw material for the production of bio energy is emerging as a new
Waste Pulp, technology. Recently, some attempts have been made to use these residues for energy or value-added
Pollution, compounds production as strategies to reduce their toxicity levels. The present article provides an
Waste Utilization overview regarding coffee and its main industrial residues. Based on the data, it was concluded that
coffee may be considered as one of the most valuable primary products in world trade, crucial to the
economies and politics of many developing countries since its cultivation, processing, trading,
transportation, and marketing provide employment for millions of people. As a consequence of this big
market, the reuse of the main coffee industry residues is of significant importance from environmental
and economical viewpoints.

Copyright © 2015 Asrat Gebremariam Woldesenbet et al. This is an open access article distributed under the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

INTRODUCTION 2008). Coffee contains over 1500 chemical substances, 850

volatile and 700 soluble, and when prepared correctly involves
Coffee is one of the most important agricultural export
13 independent chemical and physical variables. When coffee
commodities in the world economy, next to oils and it is the
is extracted in water, most of the hydrophobic compounds,
most important and strategic commodity on which Ethiopia's
including oils, lipids, triglycerides, and fatty acids remain in
economy depends on. It has always been the most important
the grounds, as do insoluble carbohydrates like cellulose and
cash crop and largest export commodity, which account 90%
various indigestible sugars. Structural lignin, protective
of exports and 80% of total employment in Ethiopia (Addis
phenolics and the wonderful aroma-producing essential oils
Ababa, 2008). Ethiopia had been the origin of coffee since
are also present in coffee. Coffee is a major plantation crop
coffee plant was initially found and cultivated in the Kaffa
grown worldwide and is one of the most popular beverages
province (Bonga, Makira) of Ethiopia (UNCTAD/WTO,
consumed throughout the world. There are three common
2002). Coffee in Ethiopia contributes 41% of the country’s
species of coffee: robusta, arabica and liberica. 75-80% of the
total foreign exchange earnings and about 10% of the gross
coffee produced worldwide is Arabica and 20% is Robusta.
domestic product. Over 25% of the populations of Ethiopia are
dependent on coffee for their livelihoods. There are four types
Residues Generated in the Coffee Industry
of coffee production system in Ethiopia: forest coffee (10%),
semi-forest coffee (35%), garden coffee (35%), and plantation
The agro-industrial and the food sectors produce large
coffee (20%) (5% government, 15% private) (Addis Ababa,
quantities of waste, both liquid and solid. Due to the great
demand of coffee, coffee industries are responsible for the
*Corresponding author: Asrat Gebremariam Woldesenbet generation of large amount of residues, which are toxic and
School of Chemical and Bio-Engineering, Addis Ababa Institute of
represent serious environmental problems (Solange et al.,
Technology, Addis Ababa University, P.O. Box 385, Addis Ababa,
Ethiopia 2011).
1468 Asian Journal of Science and Technology Vol. 6, Issue 05, pp. 1467-1471, May, 2015

Table 1. Africa: Coffee production (Average in thousand bags of nature, without any treatment, causes severe environmental
60 kg each) pollution due to putrefaction of organic matter.

Year 1980 - 89 1990 - 99 2000 - 09 2010 -12 Coffee Industry Residues Applications
Total Africa 19888 16078 15372 15712
Ethiopia 3128 2973 4904 6450
Uganda 2724 2811 2924 3002 Nowadays, there is great political and social pressure to reduce
Cote d'ivoire 4338 3448 2692 1291 the pollution arising from industrial activities. Almost all
Cameroon 1771 1022 821 845 developed and underdeveloped countries are trying to adapt to
Tanzania 875 779 796 686 this reality by modifying their processes so that their residues
Congo, D.R. 1610 1019 383 681
Kenya 1726 1377 766 669 can be recycled. Consequently, most major companies no
Madagascar 1092 780 490 566 longer consider residues as waste, but as a raw material for
Others 2625 1868 1597 1522 other processes (Mussatto et al., 2006).

Source: (International Coffee Organization, 2014)

Fig. 1. Percent (%) share of Africa and Ethiopia in World coffee production (International Coffee Organization, 2014)

Fig. 2. Harvesting coffee for wet processing

The wastewater generated from coffee processing plant The presence of organic material and its demand of great
contains organic matter like pectin, proteins, and sugars quantities of oxygen to degrade confer a toxic nature. Despite
(Bello-Mendoza and Castillo-Rivera, 1998). Coffee pulp, one the negative characteristic and the large amounts that they are
of the principal by-products of wet processed coffee generated, there are few studies focusing on their use in
constitutes almost 40% of the wet weight of the coffee berry, different and profitable applications. Besides to add value to
is rich in carbohydrates, proteins, amino acids, poly-phenols, these unused materials, finding alternative forms to use them
minerals, and appreciable quantities of tannins, caffeine and would be useful to decrease their impact to the environment
potassium. The poly-phenols and caffeine are reported to be (Solange et al., 2011).
the anti-physiological factors on animal feed. Hence, coffee
pulp has to follow a preliminary treatment before it is used Processing of Coffee
(Sebastianos et al., 1998). Coffee pulp is generated to the
extent of 40% in the fermentation of coffee berries poses many There are two ways by which coffee can be processed: wet
problems in the coffee producing countries. Its disposal in (fermented and washed) and dry (natural) processing. In most
1469 Asian Journal of Science and Technology Vol. 6, Issue 05, pp. 1467-1471, May, 2015

cases, wet processing is regarded as producing a higher quality

product.

Wet Method

Approximately half of the world coffee harvest is processed by

the wet method in which the coffee berry is subjected to
mechanical and biological operation in order to separate the
bean or seed from the exocarp (skin), mesocarp (mucilagenous
pulp) and the endocarp (parchment) (Clark, 1985). Pulp
represents about 40% of the weight of the fresh fruit and
presently is underutilized, causing serious pollution problems.
In wet method, the de-pulping involves the removal of the
outer red skin (exocarp) and the white fleshy pulp (mesocarp)
and the separation of the pulp and beans. Immature cherries
are hard and green and very difficult to de-pulp. If the coffee is
to be wet processed, correct harvesting is essential. For small-
scale units, the cherries can be de-pulped in a pestle and
mortar, and is very labor intensive.

Dry Method

In dry method, the coffee cherries are dried immediately after

harvest. This is usually sun drying on a clean dry floor or on
mats. The bed depth is less than 40 mm and the cherries are
raked frequently to prevent fermentation or discoloration.
However, there are problems associated with this method. The
most serious problem is dust and dirt blown onto the product.
Another problem is rainstorms often appear (even in the dry
season) with very little or no warning. This can soak the
product very quickly. Labor has to be employed to prevent
damage or theft. Sun drying is therefore not recommended. Fig. 4. Waste disposal
The dried cherry is then hulled to remove the pericarp. This
can be done by hand using a pestle and mortar or in a The better utilization by biotechnological means assumes
mechanical huller. The mechanical hullers usually consist of a social, economic and industrial importance. The wastewater
steel screw, the pitch of which increases as it approaches the from agro industries has high concentration of organic
outlet so removing the pericarp. pollutants. So it’s very harmful for surrounding water bodies,
human health and aquatic life if discharged directly into the
surface waters. People residing in the vicinity of agro
industries utilizing the stream water for domestic purposes
suffer from severe health problems (Alemayehu and Rani,
2008). The seriousness of the situation is shown in Table 2.
From this it is obvious that some people were suffering from
one problem while others were having cumulative health
effects. Agricultural practices such as use of organic
herbicides, inorganic and synthetic pesticides, efficiency of the
uses of inorganic fertilizers, etc., determines the environmental
issues arising from them. For instance, the use of agricultural
pesticides significantly changes the toxic characteristics of the
wastewater (Chanakya and Dealwis, 2004).

Table 2. Health problems reported by the population living

nearby industries (Alemayehu and Rani, 2008)

Health problems % of population affected

Fig. 3. Sun drying of coffee for dry process
Spinning sensation (feeling drunk) 89
Eye irritation (burning inside) 32
Problems of Coffee Waste Skin irritation 85
Stomach problem 42
Agro-industrial residues/wastes are generated in large Breathing problem 75
quantities throughout the world. Their non-utilization results in Nausea 25
loss of valuable nutrients and environmental pollution.
1470 Asian Journal of Science and Technology Vol. 6, Issue 05, pp. 1467-1471, May, 2015

Coffee pulp/husk contains some amount of caffeine and In addition, the presence of some toxic chemicals – alkaloids,
tannins, which makes it toxic resulting in disposal problem. tannins, and poly-phenolics makes the environment for
However, it is rich in organic matters, which makes it an ideal biological degradation of organic material in the wastewater
substrate for microbial processes for the production of value- more difficult. The main ecological effect of organic pollution
added products. Several solutions and alternative uses of the in a water course (into which effluents have been discharged)
coffee pulp and husk have been attempted. These include is the decrease in oxygen content. The organic substances
fertilizers, livestock feed, compost, etc. diluted in the wastewater break down very slowly by
microbiological processes, using up oxygen from the water.
Management of Coffee Waste Due to the decrease in oxygen content, the demand for oxygen
to break down organic material in the wastewater exceeds the
Having known the problems of coffee waste, several attempts supply, dissolved in the water, thus creating anaerobic
have been made to manage. Coffee pulp solid waste is being conditions.
converted into compost, which was used by the suppliers in
fertilizing their coffee farms. Waste water management The amount of oxygen needed to biologically break down
techniques used by the coffee pulping operators are based on organic wastes diluted in water (BOD) could be as high as
the use of lagoons. 15,000 mg/l, while the amount of dissolved oxygen required to
combine with chemicals in the wastewater (COD), could be
Table 3. Characteristics of effluent wastewater from conventional between 15,000 and 25,000 mg/l. The resulting anaerobic
wet coffee processing plants conditions can be fatal to aquatic creatures and also cause bad
odour; moreover, the bacteria cause health problems if the
Parameter Mean + SD discharge standard (Ethiopia EPA) wastewater seeps into a source of potable water. Another
pH 4.13 + 0.23 6-9 environmental problem is the high requirement of water for
BOD5 mg/L 1697 + 391 80
coffee processing; as much as 15,000 litres per tonne of
COD mg/L 5683+ 304 250
NH3 mg/L 4.51 + 1.62 5 cherries (coffee fruit) can be used, if there is no recycling and
NO3N mg/L 3.39 + 0.65 20 reuse (UNCTAD/WTO, 2002). In Ethiopia at present, there
PO43- mg/L 3.32 + 0.5 5 are more than 1026 wet coffee processing installations
TSS mg/L 1975 + 322 100
processing 1000 tons of coffee cherry daily on average and a
TDS mg/L 1801 + 245 3000
DO mg/L 2.14 + 0.72 - number of industries under construction. About 15 liters of
Source: (Tsigereda et al., 2013) water is required to recover 1 kg of clean green coffee beans.
The effluents from the processing industries are directly
Environmental Issues discharged to the river streams. Waste water from pulping,
fermentation and washing of coffee beans presents series
The coffee process has been causing environmental problems problem on receiving environment especially on water bodies.
at the local level not only due to the consumption of water, but
more due to the discharge of effluents with large volumes of Conclusion
organic waste. Pollutants in coffee wastewater emerge from
the organic matter set free during pulping, especially due to In coffee producing countries, coffee waste constitutes a
the difficulty in degrading the mucilage layer surrounding the source of severe contamination and serious environmental
beans. The organic and acetic acids from the fermentation of problems. For this reason, since the middle of the last century,
the sugars make the wastewater very acidic (with pH as low as efforts have been made to develop methods for coffee waste
3.8), a condition in which higher plants and animals can hardly treatment and management, also its utilization as a raw
survive. Moreover, the total suspended solids in the effluents material for the production of feed, beverages, vinegar, biogas,
are high; in particular, the digested mucilage, when caffeine, pectin, peptic enzyme, protein, and compost. Hence,
precipitated out of the solution, builds a crust on the surface, there is a need to curb these problems through innovative and
clogging up waterways and further contributing to the eco-friendly techniques. So, this documentation may be an eye
anaerobic conditions. opening for the area. Presently, coffee waste management
systems in Ethiopia are not operating. They could reduce on
Table 4. Composition of coffee waste their losses if they employ qualified staff and adopt modern
management techniques. Therefore, unless they improve their
Pulp Mucilllage profitability, they will consider demands to take an additional
Contents
Proportion
Contents
Proportion investments, e.g. for environment as a burden. Many by-
(%) (%) products from wet coffee processing offer additional sources
Ether extract 0.48 Water 84.2 of revenue, employment and new enterprises. It is therefore
Crude fiber 21.4 Protein 8.00
Crude protein 10.1 Reducing sugar 2.50 high time that coffee waste started to put a price.
Ash 1.50 Non-reducing sugar 1.60
Nitrogen free extract 31.3 Pectin 1.00 Acknowledgements
Tannins 7.80 Ash 0.70
Pectic substances 6.50
Non-reducing sugars 2.00 The authors are thankful to School of Chemical and Bio-
Reducing sugars 12.4 engineering at Addis Ababa Institute of Technology, AAU for
Chlorogenic acid 2.60 financial, technical support and laboratory facility during the
Caffeine 2.30 research work. Asrat Gebremariam Woldesenbet would like to
Total caffeic acid 1.60
thank Bonga College of Teacher Education for providing
sponsorship for his PhD study.
1471 Asian Journal of Science and Technology Vol. 6, Issue 05, pp. 1467-1471, May, 2015

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