Over 120 000 tons coffee is processed per year in Kenya. More than 1200 coffee factories produce a pollution loading equivalent to a staggering population equivalent of over 240 000 000. The coffee industry is therefore the most important industrial polluter in rural Kenya. Pulp, husks and wastewaters are produced. Husks can be directly used as fuel. Wet pulp could be composted and then used as a soil conditioner. Wastewaters have a high BOD5 sometimes even exceeding 9000 mg/l. In India and Central American countries, anaerobic lagoons are mainly used for the treatment of these wastewaters. In Keftya water re-use combined with land disposal with zero discharge has been recommended. However, in all these methods, the desired environmental soundness is rarely achieved. Anaerobic digestion with biogas production is potentially attractive. Fuel generated could be used for drying coffee. About 10 000 GJ of energy is required to dry 1 ton of coffee. The potential yield of biogas from one ton of pulp can be estimated as 131 m3. This is equivalent to 100 litres of petrol in fuel value.
Start-up of a “zero-discharge” recirculating aquaculture system using woodchip denitrification, constructed wetland, and sand infiltration
