Report

Polycultures - A step towards sustainability

Report about a meeting in Waedenswil, Switzerland

By Andreas Schoenborn-Schaller, Switzerland

More information and downloads of the Waedenswil meeting can be found at http://www.cascadesystems.ch/ [in German language]

Introduction

Polyculture is the integration of several cultures into one system, which generates multiple benefits arising from the single steps as well as from the system as a whole. The promotion of polycultures has been a key focus of Ecological Engineering for a long time. A meeting on April 25, 2003 at the University of Applied Science (UAS) in Wädenswil, Switzerland, gave an inspiring impression about what polycultures can look like, and summarized the state of the art in Switzerland of today.

Fig. 1: Andreas Graber of UAS Waedenswil explaining his polyculture research setup after lunch break at the polyculture meeting, April 25, 2003

Baobab Farm, Mombasa, Kenya

The meeting was opened by René Haller from Mombasa, Kenya, the founding father, director and "spiritus rector" of the Baobab Farm in Mombasa. Baobab Farm, in short, is a huge farm on the Kenyan coast that is situated in former quarries that were left completely barren after the excavation of limestone by the Bamburi Cement Factory. Haller, an agronomist, was asked to start the rehabilitation of this wasteland in 1971.

With a strong vision of creating a lush, self sustaining ecosystem that would yield benefits for the local population as well, with good support by the company management and a good portion of luck as well, Haller managed to help create what may be called a piece of paradise. Tropical vegetation was brought back to the quarries, and with them a multitude of animals came - birds, insects, monkeys, antelopes and many more, some by themselves, some by Haller and his team.

The Baobab Farm is now producing a variety of products, many of which are wanted in the area and can be sold on the local markets. Examples are: Tilapia fish, antelope and crocodile meat, vegetables of various kinds, wood for timber and carving, charcoal, medical plants and many other products. Baobab Farm has also become a major tourist attraction to the nearby tourist resorts and has had up to 90'000 visitors per year (before the current crisis).

An interview with René Haller will be published in the next issue of this newsletter.

From China to the World

In the second talk, Johannes Heeb, president of IEES, gave an overview about the roots of the polyculture idea in China and how it is beginning to spread over the globe. He gave several examples from his own work and the work of other IEES members, namely in Hainan, PR China, Calcutta and Bangalore, India and the Tropical House Ruswil in Switzerland. He showed how polycultures can be used to create beautiful and income generating systems in developing as well as in developed countries, while generating multiple benefits and economic return.

The Tropical House in Ruswil, for example, will be able to produce various tropical fruit and fish in an economically and ecologically sustainable way if the current pilot size of about 1 hectare is increased to 4-5 hectares, Heeb said. Already now, it is producing tasty, high quality Papayas and Mangos as well as Tilapia for local stores and restaurants. The attention the Tropical House has been receiving in public is overwhelming, with members of the Swiss national government among its visitors. For some more information look at the Case Study Tropical House Ruswil on this website.

One major constraint for the reproduction of the Ruswil project elsewhere is the availability of energy for heating during the cold season - the equivalent of 6 MWh per year which in the case of Ruswil is supplied by a gas compression station as waste heat and is provided to the Tropical House for free.

State of the Art in Switzerland

The examples for the work in Switzerland were further detailed in the two following talks by Andreas Graber and Daniel Todt from UAS Wädenswil. Graber presented examples of work with polycultures he and his colleagues have been conducting in recent years.

One example was the experimental polyculture plant at Otelfingen, Switzerland. This polyculture system recycled nutrients and treated surplus water from a biogas generating so called Kompogas® facility (for details see also Case Study Otelfingen on this website). The system removed about half of the nitrogen and the phosphorus while producing vegetables, ornamental plants (such as Eichhornia, yes, this is an ornamental plant in Switzerland) and fish. The work in Otelfingen ended in 2000.

More recent and stil ongoing work is conducted at the Tropical House Ruswil (see above) and at the aquaponics research facility at UAS Waedenswil, which we were also able to visit after lunch. The system in the UAS greenhouse is a polyculture driven by rainwater and fish fodder. The effluent from Tilapia (Oreochromis niloticus) fish basins is either cleaned in vegetated hydrofilters (where e.g. tomatoes and bananas are grown) or used for irrigation of vegetables. Based on their experiences, Graber and his colleagues are advocating a broader use of these polycultures (they also call them "Cascade Systems") in Switzerland.

After the post-lunch tour through the greenhouse, D.Todt presented an outlook how "waste" areas in Western cities (such as rooftops) in combination with waste heat could be used in the future to create small oases in our grey cities.

Composting Fecal Matter in Kumasi, Ghana

Last but not least, some work done by SANDEC was presented by Dyonis Forster who showed an example from Kumasi, Ghana. Kumasi is one of the biggest market towns in West Africa. There, SANDEC and the local administration are trying to set up a system for the co-composting of fecal matter from pit latrines with organic household wastes. Up to now, the fecal matter from pit latrines has been disposed somewhere on the open field or into open waters, thereby causing a major risk for public health.

The fecal matter is dewatered, shoveled to compost heaps and composted for 2 months. After this period, the compost is considered hygienically safe. However, it contains a disappointingly low amount of nutrients (1 % N, 0,4% K, 0,4% P). Since the co-compost is competing with chicken manure on the local market (which can be picked up by the farmers for free), its chances are rather limited.

A Personal Summary

My impression after this very inspiring meeting is that the idea of polycultures is well on the way in Switzerland. Today we are still on the stage of experimental setups and pilots. However, the development of these systems may pick up quite some speed as soon as agro-business jumps in. And there is considerable interest in them.

The polyculture idea has a great potential for both efficient food production and minimization of the impact on the neighbouring environment. The idea of closed nutrient cycles looks sympathetic to environmentalists, so does the multifunctionality, the integrative approach, the reuse and recycle aspects. Whether the agro factories that may grow out of these principles would be still all so sympathetic is a question I can't answer.

Joe Swamp, who has been critically accompanying this newsletter for a while, has his own private nightmare about them (see Joe's Corner, this newsletter).