Water hyacinth spawns mushroom enterprise

Although wild mushrooms form a significant part of the traditional diet of many African families, mushroom culture is not widely practised. This is despite the fact that Africa is home to one-quarter of the world's mushroom species, many of which could, in theory, be cultivated. A project that has now spread to eight countries in sub-Saharan Africa is challenging this tradition and, not only has it provided a new cash crop, but it is also providing a means of recycling waste materials.

The water hyacinth (Eichornia crassipis) has been described as 'public enemy number one' in many parts of southern and eastern Africa. The floating plant, introduced for its potential as an ornamental flower, quickly escaped and has since spread throughout the region's waterways. Large areas of Lake Victoria, for example, are covered by the weed, which has also choked the life out of Kenya's Nairobi Dam. Now, however, rather than perceiving the plant as a weed to be exterminated, a project coordinated by the ZERI (Zero Emissions Research Initiative) Foundation has begun using it as a substrate for mushroom production.

The possibility of growing mushrooms on a water hyacinth substrate was first demonstrated by Professor S.T. Chang of the Chinese University of Hong Kong, and was put into practice by Margaret Tagwira, a laboratory technician at the African University of Mutare in Zimbabwe, whose work has been supported by ZERI and the United Nations Development Programme. When the ZERI programme began, however, the only mushroom species being grown in Africa was the typical white button mushroom (Agaricus bisporus). Since then, thanks to the work of Margaret Tagwira, other species have been successfully cultivated, including the oyster mushroom (Pleurotus) and the wild Reishi mushroom (Ganoderma lucida).

Having succeeded in growing oyster mushrooms, Margaret Tagwira then set about testing whether their commercial production was a viable proposition. Within a few months, with the help of two full-time and two part-time staff, a demonstration mushroom farm was yielding 40 to 50 kg of mushrooms per day, worth about US$55 to US$70 on the local market. Margaret also introduced the concept of distributing bags of compost seeded with mushroom spawn that could be buried in villagers' vegetable patches. These bags would be kept moist as the gardens were watered, and mushrooms harvested at the same time as the leafy green vegetables were collected for the evening meal.

Traditionally in Africa, wild mushrooms were collected at the start of the rainy season by women and young girls. In this way, knowledge of which mushroom species are edible was passed from generation to generation. However, as more and more African girls now receive full-time education, this indigenous knowledge is being lost and many people are now reluctant to eat wild-picked mushrooms. Access to home-grown mushrooms, or cultivated mushrooms from the local market is helping to fill this gap. "Mushroom farming projects supported by ZERI are now operational in eight African countries," says Professor Gunter Pauli, director of the ZERI Foundation, and clearly there is an opportunity for further mushroom cultivation in Africa on both subsistence and commercial scales.

This expansion can only be aided by the widespread distribution of the water hyacinth, which provides a free, almost unlimited resource for their production. In the case of the Nairobi Dam, for example, there are more than adequate supplies of the aquatic weed. In fact, once intended as the 'drinking fountain' of Nairobi and a venue for yachting regattas, the dam is now severely polluted by industrial waste, untreated sewage and soil run-off. With the water full of nutrients, the water hyacinth has flourished. However, millions of dead and dying plants have sunk to the bottom and decayed, eutrophying the lake. "None of the traditional solutions to water hyacinth control, either chemical sprays or biological control agents such as insects, have addressed the problem," adds Professor Pauli. "But how could scientists even resort to the importation of non-native insects to fight this pest? Solutions to Africa's problems should be home-grown. The water hyacinth is trying to clean up the Nairobi Dam mess, recover the nutrients and convert this massive pollution into useful biomass." What better way to use this 'waste' than to produce mushrooms - a vital food, and potentially a very lucrative crop for African farmers.