The application of the Zero Emissions Research and Initiatives (ZERI) concept in an integrated industry-polyculture-farm system in Namibia: The case of Tunweni Sorghum Brewery

Abstract

One major area dealt with by the concept of Zero Emissions Research and Initiatives (ZERI) is the utilisation of huge volumes of nutrient-rich waters from household toilets, kitchen sinks and municipal and organo-industries for integrated purposes. The arrangements at the Tunweni Sorghum Brewery, Tsumeb, Namibia are such that wastewater is utilised in the polyculture of locally available riverine fish species in large (3 000m²; 120m long x 25m wide), deep (3m) earthen ponds. Before reaching the fishponds the wastewater passes through a series of bio-system processes such as mushroom and earthworm beds, a pig sty, anaerobic and aerobic digesters and algae ponds. A pH of about 8.0 is desirable for maximum fish production in the large (9 000m³) fishponds. The old Chinese technique is followed whereby wastewater is utilised for growing fish without adding any feed supplement; various plankton and invertebrates produced naturally serve as feeds for various kinds of fish feeding at different trophic levels. A variety of locally-available riverine fish species, of different trophic levels, are useful for sustainable stocking in the ponds where no feed-supplement is necessary. Various plankton and invertebrates are produced naturally as feeds for the various kinds of fish feeding at different trophic levels, obviating the purchase of costly artificial feeds which can make fish culture uneconomical. Fish wastes are naturally mineralised into nutrients in the ponds and the nutrient-rich water supports phytoplankton, zooplankton and invertebrates, all of which comprise a varied food chain supporting the fish growth.


Keywords: Zero Emissions Research and Initiatives; wastewater; integrated poly-aqua-farm; bio-digester; sorghum brewery; Namibia


(Afr J Aqua Sci: 2000 25: 71-75)