1. Environmental Impact Assessment studies and process audits were made for three different agro-processing industries (Output 1).

Cassava starch and sago production in Tamil Nadu, India.
Cane sugar production in Mauritius .
Coffee production in Kenya.

From these studies, the coffee industry of Kenya was selected for more detailed study.

2. The methodology followed three parallel lines of approach. The first was to conduct surveys of coffee process plants including mass balances of coffee cherry in, water usage, coffee bean and discharge solids out. The second was to investigate current practices of waste-water treatment and evaluate alternatives which would be more cost effective and technically efficient. The third was to examine the patterns of water usage and solids release within the process to identify methods for reducing water utilisation, the management of waste pulp, and precipitating suspended solids from waste waters before they entered the waste-water treatment system (Output 2). All studies were directed towards identifying management improvements for cleaner production.

3. Findings of research and recommended methodologies for improving environmental control of the coffee industry were collated into a manual for the coffee industry (Output 3).

4. Strategies for reducing water use and pollution on a national basis have been developed in Kenya in consultation with the Kenya coffee industry. Due to the specific characteristics of the coffee process these strategies will find application in other countries producing coffee by the wet process rather than to agro-industries at large, though the general principles of water reduction and process control will apply to all (Output 4).

Environmental Impact Assessment studies

Distinct differences in the environmental impact potential were evident for the starch, sugar and coffee industries. The environmental impact of the Indian starch industry related to visual impact and odour generated by static ponds of starch effluent, but negative impact on ground water quality was minimal. In Mauritius, sugar processing waste-waters had a significant impact on inland surface water due to poor lagoon management at factory level. While being important, the environmental impact of the sugar industry was of lower impact than pollution from phosphates and nitrates from agricultural run-off and municipal and industrial effluents. In the past, poor coffee waste management in Kenya has led to critical anaerobic conditions in rivers flowing from coffee producing areas whose water is used for agriculture, livestock, aquaculture and domestic use. The coffee industry, on average, was using four times the volume of water required under legislation. Surface water bodies were being contaminated with high COD soluble solids due to decomposition of coffee pulp waste, and waste-water treatment systems were prone to blockage and consequent overflow into water courses during the rainy season.

Waste-water control and reduction in water requirement for coffee processing.

The contamination of water courses from heaps of decomposing coffee pulp can be controlled through pressing the pulp. Pressures of 175 psi (1207 x 103 Pascal) partitioned 100 parts of pulp into 50 parts press cake and 50 parts press liquor. The addition of lime to complex pectins as calcium pectate improved the handling texture of the pulp but not the efficiency of liquor released. Press cake can be easily removed off site for possible use as animal feed or mulch. The liquor can be treated by pit or anaerobic digestion systems.

The typical high water usage of the wet coffee process at 80 m3/tonne of dry parchment coffee can be reduced by about 70% by the application of counter-current rather than the traditional co-current flow. While this reduces the volume of water in the system it also concentrates the effluent for subsequent treatment.

Suspended pectins, which comprise approximately 50% of the effluent solids and originate from the important mucilage removal stage of the process, can be precipitated out of suspension in waste water by simple treatment using cement as a flocculant.

Five systems were evaluated for their efficiency for removing COD from coffee waste-waters. Efficiencies were: a) traditional pit system @ 5-15%; b) improved pit @ 30-80%; c) trench @ 40-85%; d) Upward Anaerobic Sludge Blanket (UASB) @ 65%; and e) Pond systems of varying hydraulic retention @ 55-80%.

All findings and costs for improving environmental management have been presented in a handbook to the coffee industry entitled " The management of the water effluent in the coffee industry of Kenya". The technical findings have been developed into a strategy for the Kenyan coffee industry which, although being specific to the international wet coffee industry, can be applied to all agro-processing industries using large volumes of water.

The project has provided coffee processors with the principles and practices of effluent control. These can be adopted through a stepwise approach, although ideally a full evaluation of the recommended interventions should be monitored in a pilot plant.

The adoption of pulp pressing, counter-current flow, and improved water treatment within the process and as an effluent, will enable the industry to control both its discharges, and meet the legal requirements for water usage without compromising the quality of the final coffee.

1. Preliminary Environmental Assessment: Cane Sugar Production in Mauritius, September 1996. Environmental Resources Management (ERM).

2. Preliminary Environmental Assessment: Starch and Sago Production in Salem District, Tamil Nadu, March 1996. ERM

3. Preliminary Environmental Assessment: Coffee Production in Kenya, August,1996,ERM.

4. Alleviation of Water Pollution from Agro-Industries in Developing Countries: Coffee and the Environment Workshop, Kenya December 1997. ERM

5. Alleviation of Pollution from the Coffee Processing Industry in Kenya - A Review of the Source of the Problem in the Coffee Cherry, April 1998. John Wood, Natural Resources Institute.

6. Technical reports on visit to CRF Ruiru, Kenya, October - December 1997, and April- June 1998, J Noble, University of Leeds

7. Laboratory and Field Trials on the De-watering of Coffee Cherry Pulp using Bridge and Screw Presses. May-July 1998, Stafford Head and Graham Anstee, Natural Resources Institute.

8. Water Quality Survey along the Ruiru River, September 1998, JK Mburu and PK Mwaura, Coffee Research Foundation.

9. The Management of Water Effluent in the Coffee Industry of Kenya. April 1999, NRI/CRF/Leeds University and ERM.

200 copies of the handbook on "The Management of Water Effluent in the Coffee Industry" will be distributed to the coffee processors in Kenya via the Coffee Research Foundation. A simple broad-sheet outlining the key recommendations will also be distributed for use by factory workers.

CRF are preparing projects to investigate appropriate uses for the coffee pulp press cake.

A paper on the findings will be prepared for publication in a suitable technical journal.

Subject to funding, the project findings will be presented to a wider audience at an international conference on treatment of agro-industry effluents. Funding sources for the establishment of a pilot plant incorporating the recommended technologies will be investigated.

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