EcoEng Newsletter No. 12, June 2006

Optimising waste flow in a printing plant at Limbe, Cameroon

Report from a practical student assigment
Content No. 12/06
  Title page / Index
  Water from the well
  Phototrophic biofilms
  optimising waste flow
  India: Water supply
  schemes in a slum
  Austria: Sewerless city
  Composting: Ch. 5
  PNG: Ecosan project
  Biopros project
  Ecosan curriculum CD
EcoEng News:
  Joe Swamp
Various issues:
  IEES Writers' Fund
  Mailing list
  EE-Newsletter Flier
By Nico Siegenthaler, Tobias Graf and Dr. Ranka Junge (advisor)

University of Applied Sciences Waedenswil, Dept. Natural Resource Sciences,
CH 8820-Waedenswil, Switzerland

Contact of the main authors:




Since 2003, the University of Applied Sciences Waedenswil, Switzerland offers a study program of Natural Resource Sciences ( Beside theoretical subjects a focus is placed on practical training. This takes form of frequent individual tasks, problem based learning, term theses, and recently also as a practical training abroad.

The objective of the practical training is to provide students interested in international relations who intend to work in this field upon completion of their studies with an opportunity to gain first-hand experience in a project in a developing country. The host institution can be a research institute, an NGO or a private enterprise within the field of natural resources. During the practical training, the student is integrated in a team and works on a specific topic.


The term thesis on material flows

Fig. 1: Presprint at low tide

Due to the world wide population growth, the issue of ecological waste management has gained immensely on importance, especially in developing countries. Many ecological problems were created by new technologies of the industrial countries. This is why development organisations are not only working in the economic and social area but also increasingly in the ecologic sector.

Prompted by our interest in development cooperation, and in the African continent, we contacted the evangelical organisation mission 21 ( in order to find an assignment. Mission 21, which is based in Basel, Switzerland, is active globally in about 150 projects, focussing on issues such as: poverty reduction, health promotion, improvement of the position of women, peaceful resolution of conflicts and education in theology and the church.

In Limbe, Cameroon, Mission 21 (in cooperation with the Presbyterian Church of Cameroon PCC) operates the most modern printing plant of the region. Presbyterian Printing Press (PPP) or briefly Presprint has been led for the last 15 years by Mr. W. Steidle, a print expert from Switzerland, . Today, Presprint employs up to 150 workers, and the machines work round-the-clock.

The management of Presprint has acknowledged the importance of ecological issues. As a first step towards improving the ecological situation, the current waste management of Presprint was analyzed. In our term thesis (Graf & Siegenthaler 2005) we quantified the environmental risks, and demonstrated a large potential for recycling.

In order to find the best possible solutions for the modification of waste management, the ecologically hazardous goods used by Presprint were identified and examined. Furthermore the substance flows were optimized by the application of new processes.

The substance flow analysis consists of four steps (Baccini & Bader 1996):

  1. Definition of system boundaries and description of the system
  2. Listing of the material flows
  3. Graphical visualisation and interpretation
  4. Identification of intervention and regulation alternatives
Figure 2: Current and target state of the substance flow at Presprint (click to download PDF 44 kB with details)

Thus, the current state of the substance flow in the printing plant was graphically set in contrast to the target state (Figure 2). This way, the scope for improvement was visualised. Alternative scenarios for improvement were explored.

For several ecological issues no standard solution existed and tailor made solutions had to be developed that would also work under African circumstances. In order to identify appropriate suggestions for the disposal of the output goods of the print plant, we extensively consulted literature, and talked to printing experts in Switzerland (Holcim Switzerland, AMRA Farben AG, Sun Chemicals). As a result, the target process was defined into which the output goods leaving Presprint should be directed. Different target processes with the same reutilisation pathway were consolidated to key processes. From these key processes the basic scenario was designed which served as foundation for the suggested solutions.

After evaluating the advantages and disadvantages, a modified version of the so-called "cement works" scenario proved to be the best possible solution for Presprint (Figure 2). This includes the following suggestions:

  • The amount of Presprint waste paper processed in cardboard production in Nigeria, should be maximized. On the raw material level this is the better disposal method than the combustion of Corg (organic carbon) in the cement works.
  • Nevertheless, a fraction of waste paper should be used as fuel for the incineration of the mixture of paints, varnish and saw dust in the "thermal" treatment in the cement works.
  • Next to paper products, the detergents contain the highest levels of organic carbon. We suggested, that detergents should be re-utilized through distillation or filtration.
  • Currently, the aluminium print plates are being handed out to the population. They are used as roof cover. The production of new aluminium takes more than 20 times more energy than its recycling. Therefore aluminium should be recycled. This also generates income which can be used for further investments to improve the ecological situation of Presprint.

Implementation in Cameroon

Fig. 3: Dumping site at Limbe, Cameroon

The biggest challenge of the term thesis assignment was that our research took place in Switzerland, while the printing plant is located in Cameroon. The communication with the people in charge in Cameroon was time-consuming and could not quite substitute field work. This is one of the reasons, why we endeavoured to implement our study on-site, in Cameroon.

After some weeks of intense paper-work and a preparatory seminar at mission 21, we finally arrived in Cameroon on a hot October day. During the first week we got to know the town, then we had three months to implement our term thesis.

Immediately we had to revise some of our preconceived opinions.

The environmental awareness as integral part of an enterprise is very much promoted by the Presprint management. PPP is situated directly at the sea shore (see Fig. 1), with a canteen on the beach. With every flood large amounts of rubbish are washed ashore. On the third day upon arrival already, we helped vigorously in the action "keep the beach clean" together with employees of the PPP.

Currently, the waste of the printing plant is either incinerated openly or deposited in a landfill (see Fig. 2). The unprotected, mixed landfill is operated by the town of Limbe. Once in a while, the dump is burned down to reduce the waste volume. In this landfill, printing inks and varnish which would have to be treated as a hazardous waste are disposed of, too. In the direct neighbourhood of the landfill there are extensive plantations of oil palm (Elaeis guineensis) and plantain (Musa paradisiaca normalis). It is unclear whether the emissions from the landfill influence the quality of the plantation products.

As the best solution for the improvement of the waste management of Presprint we proposed the combustion in a cement works. The management appreciated this suggestion, but to our disappointment the cement factory is only in planning, and will probably only be constructed within the next six months or so. Because of this, no negotiations could be held with the management. The general manager of the printing plant assured us, that after the arrival of the future cement-plant management he will proceed to negotiate this option. The thermal treatment in the cement works would be a huge success but it is depending on the kind of energy source used (coal and oil) and the addition of alternative combustible. The saw dust can be delivered by the church intern manufacturer.

To reduce the costs of the option "cement works" it was concluded that a distillation machine for the detergents would not be purchased. In this particular case the question came up if the detergents should be kept in the cement works or be used to fight malaria in the population of Cameroon.

The aluminium printing plates are still granted to the population for their houses. The cost of transport back to Europe for purposes of recycling would be prohibitive. After long search an aluminium plant was found in Cameroon, now it is up to the Management of Presprint to organise this.

The recovered paper of the PPP is already recycled for egg carton production in Nigeria, so this path of progress was covered.

Furthermore, we analysed the sewage system of Presprint on the basis of the material flow analysis and the product flow analysis. The current state of the product flow in the printing plant was compared graphically to a possible target state. This visualization showed room for improvement. Our analysis showed that the effluents were filtered by volcano stones on the beach and trickled into the porous ground or were disposed in the sea.

Figure 4: Pilot Constructed wetland built at Presprint, Limbe, Cameroon during our stay

Based on the current technical and financial possibilities of Presprint a constructed wetland seemed to be the best solution for the problem. Thus, we contacted our advisor Dr. R. Junge to provide us with literature on planted soil filters. This, together with some analyses of wastewater-flows enabled us to do the necessary calculations for the dimensioning of the wetland. A pilot wetland was constructed with the financial and technical support of the Presprint management and its workers (Figure 4).

However, which local plants are suited for this purpose? Typha, a plant usually used in Europe, does not grow here. We contacted the local botanical garden, an independent botanical expert, several plant urseries, consulted the library in Limbe, the internet, and talked to Presprint-employees. The information gathered resulted in our decision to use Pennisetum purpureum (Elephant grass). This plant belongs to the family of grasses (Poaceae). It has a bamboo-like appearance, with its stout, "woody" older stems. It grows as weed along dikes and ditches. Additional internet searches yielded several papers where P. purpureum was used in constructed wetlands for wastewater treatment, and as an alternative feedstock in kiln of ceramic industry. With the help of the local people we could gather enough seedlings for planting the constructed pilot wetland and finish our work before departure to Switzerland.


Concluding remarks


Our practical training in Cameroon was an exciting experience with many new cultural and also culinary impressions. We met amazingly friendly and hospitable people who contributed vastly to make our sojourn in Cameroon so memorable.




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BUWAL (1998): Abfall/Luft, Richtlinie, Entsorgung von Abfällen in Zementwerken.

Fehringer, R. et all (1997): Auswirkungen unterschiedlicher Szenarien von der thermischen Verwertung von Abfällen in …sterreich (ASTRA). TU, Wien.

Graf, T. & Siegenthaler, N. (2005) Variantenerarbeitung zur Abfallentsorgung der Druckerei Presprint in Kamerun anhand einer Stoffflussanalyse. Term Thesis, Hochschule Waedenswil.

Bahlo, K. and Wach, G. 1992. Naturnahe Abwasserreinigung. Oekobuch Verlag, Staufen bei Freiburg.

Fallshaw, D. (1993): Printer and the Environment. British Printing Industries Federation (BPIF), London.

Martinetz, Ch. (1999): Lexikon der Entgiftung von Abgasen, Abwässern, Abfälle und Altlasten. Verlag Harri Deutsch, Thun, Frankfurt am Main.

Mission 21 (2005) Kamerun, Limbe: Druckereiausbildung als Chance für Jugendliche, Projektblatt Projekt-Nr.: 134.1045 (

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Yang, L., Chang, H.T., Huang, M.N.L. (2001) Nutrient removal in gravel- and soil-based wetland microcosms with and without vegetation. Ecological Engineering 2001, 18(1): 91-105.

© 2006, International Ecological Engineering Society, Wolhusen, Switzerland